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  • 251.
    Karlsson, Andreas
    et al.
    University of Skövde, School of Engineering Science.
    Butoyi, Guy Igor
    University of Skövde, School of Engineering Science.
    Teknisk analys av felkällor kring äggpaketeringen hos DAVA Foods i Skara: med hjälp av produktionstekniska metoder och verktyg2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    DAVA Foods is a food industry that is one of Sweden's largest companies in the processing and packaging of eggs. The company on which this degree project is carried out in is located in Skara and the work has its main focus on the packaging process of the 24-pack as well as 10-pack egg cartons sold for grocery shopping.The thesis work is to do a technical analysis of sources of errors regarding the egg packaging at DAVA Foods. Students will use various production engineering tools to identify and evaluate improvement proposals on 24-packflow. Students will also identify and evaluate improvement proposals on 10-packflow and identify and evaluate improvement proposals to better alert staff when stops occurs in the process.The PDCA planning tool was used to plan and structure the work once and then a current analysis of flows was made. To gain a better understanding of the current state of the process, observations and interviews were used for data collection. The current position analysis was the base for the work's implementation phase where the root cause tool five why and the fishbone chart diagram was used to find root causes for found problems.The technical analysis of flows resulted in the creation of fourteen improvement proposals, of which eight of these improvement proposals belong to 24-packflow and the remainder to 10-packflows. A pick chart was then used to show which improvement proposals the students believe the companies should implement.The conclusion is that there are two improvement suggestions that should be considered in the 24-packflow. These are to smooth the flow with a new wrapping machine and to extend the conveyor belt, which would reduce wastage that occurs in the process.For 10-packflow, there are two improvements suggestions that should be implemented. These are the implementation of new boxes that have a different lock mechanism than the current ones, and the installation of new light beams to alert the staff the different conditions of the process. A rebuilding of the denester that supplies the flow with the packages, where the task of the denester is to separate the bottom package from the magazine and transport it further to the rotary machine that reverses the package, should also be considered to reduce losses that occur as a result of the packages being damaged in the magazine as the package pile bends when these have been stacked too high.

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  • 252.
    Karlsson, Daniel
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre. Production Engineering, Componenta, Nossebro, Sweden.
    Linnéusson, Gary
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre. Production Engineering, Arkivator AB, Falköping, Sweden.
    Systemic change management: An opportunity for manufacturing organizations2008In: Proceedings of the 18th International Conference on Flexible Automation and Intelligent Manufacturing: FAIM 2008 / [ed] Leo J. de Vin, 2008, Vol. 1, p. 654-659Conference paper (Refereed)
    Abstract [en]

    This paper examines potential opportunities at two SMEs (small to medium-sized enterprises) to improve the decision making process for change in their manufacturing organizations. Present procedures of the decision making process for manufacturing system development have been studied by applying feedback systems thinking. A framework for systemic change management is proposed utilizing a bottom-up perspective to acknowledge individual competence and creativity. In conclusion applying system principles facilitates an environment for proactive developments towards a learning organization.

  • 253.
    Karlsson, Ingemar
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    An interactive decision support system using simulation-based optimization and knowledge extraction2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The use of simulation to improve existing manufacturing systems is not new, but simulation can also be used increase the understanding of production systems that have not yet been built. The power of simulation models can be further enhanced by using simulation-based optimization, in which an optimization algorithm tries to find optimal solutions, given certain objectives. However, extracting knowledge from the data resulting from simulation experiments and simulation-based optimization is a complex task. Therefore, tools are needed to assist users in this task. These tools can be visual, like diagrams, or can be generated by data mining. The process of running a study using simulation-based optimization to extract knowledge is a manual task that can in part be automated using existing tools, but to the author’s knowledge there is no software that implements the complete process. This work aims to develop a novel decision support system to support the generic decision process when using simulation and simulation-based optimization. The first step in setting up such a system is to understand how industry currently uses simulation and simulation-based optimization in manufacturing operations. Thus a questionnaire was distributed to manufacturing companies and organizations. The results showed that these techniques are being used, but that companies want more help with the analysis of the results as well as an automated guide in the decision process. This work proposes a system that supports a generic decision process by providing a tool with which a user can define a workflow in their organization, using simulation-based optimization as one component. The decision support system then provides tools for extracting knowledge in the form of diagrams and performs data mining for automated analysis. Data mining is part of the workflow as a tool for extracting knowledge after an optimization, as well as a tool for guiding optimization to suit the users’ preferences. The decision support system also provides for visualization of simulation models and optimization results using augmented reality. A head-mounted display helps users to see the results and model behaviors in 3D. This technology also makes it possible for users to collaborate, both in the same location and remotely. These visual and automatic analysis tools are shown to be effective in several application studies of real-world production scenarios in which data mining has been used to extract important knowledge that would be hard to obtain manually. Together with the automated workflow and efficient visualization of simulation and optimization results in augmented reality, the decision support system is believed to be an effective tool for extracting knowledge for general production systems design and analysis.

  • 254.
    Karlsson, Ingemar
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Bernedixen, Jacob
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Pehrsson, Leif
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Combining augmented reality and simulation-based optimization for decision support in manufacturing2017In: Proceedings of the 2017 Winter Simulation Conference / [ed] W. K. V. Chan, A. D’Ambrogio, G. Zacharewicz, N. Mustafee, G. Wainer, and E. Page, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 3988-3999Conference paper (Refereed)
    Abstract [en]

    Although the idea of using Augmented Reality and simulation within manufacturing is not a new one, the improvement of hardware enhances the emergence of new areas. For manufacturing organizations, simulation is an important tool used to analyze and understand their manufacturing systems; however, simulation models can be complex. Nonetheless, using Augmented Reality to display the simulation results and analysis can increase the understanding of the model and the modeled system. This paper introduces a decision support system, IDSS-AR, which uses simulation and Augmented Reality to show a simulation model in 3D. The decision support system uses Microsoft HoloLens, which is a head-worn hardware for Augmented Reality. A prototype of IDSS-AR has been evaluated with a simulation model depicting a real manufacturing system on which a bottleneck detection method has been applied. The bottleneck information is shown on the simulation model, increasing the possibility of realizing interactions between the bottlenecks. 

  • 255.
    Karlsson, Ingemar
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Syberfeldt, Anna
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Bandaru, Sunith
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    An interactive decision support system using simulation-based optimization and data mining2015In: Proceedings of the 2015 Winter Simulation Conference / [ed] L. Yilmaz, W. K. V. Chan, I. Moon, T. M. K. Roeder, C. Macal, and M. D. Rossetti, IEEE Press, 2015, p. 2112-2123Conference paper (Refereed)
    Abstract [en]

    This paper describes a decision support system (DSS) built on knowledge extraction using simulation-based optimization and data mining. The paper starts with a requirements analysis based on a survey conducted with a number of industrial companies about their practices of using simulations for decision support.Based upon the analysis, a new, interactive DSS that can fulfill the industrial requirements, is proposed.The design of the cloud-based system architecture of the DSS is then described. To show the functionality and potential of the proposed DSS, an application study has been performed for the optimal design of a hypothetical but realistic flexible production cell. How important knowledge with respect to different preferences of the decision maker can be generated as rules, using the new Flexible Pattern Mining algorithm provided in the DSS, will be revealed by the results of this application study.

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    An interactive decision support system using simulation-based optimization and data mining
  • 256.
    Karlsson, Louise
    et al.
    University of Skövde, School of Engineering Science.
    Sjöberg, Alexander
    University of Skövde, School of Engineering Science.
    Framtagning av snabbkoppling i polymera material för vätskekylda datacentraler2018Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of the Bachelor thesis is to create a concept proposal in collaboration with CEJN. This report is presenting activities involved in the development process used to obtain the final result.

    Referring to the expansive market for liquid cooled data centres, CEJN aims to be in the leading edge with a new quick connection coupling. This demands reduction of production costs relative their existing aluminium coupling, partly by change of material to plastics. Outsourcing is relevant as the company does not produce plastic components at set.

    The idea generation phase has been based on a pre-study consisting of literature studies, analyses of competing products through demolition, and user tests. Prototypes have been used for testing and evaluation throughout the process.

    The outer components of the quick connection coupling proved to be among the costliest details. Locking mechanism, the formation of an inner slot for seals and the junction between nipple- or coupling body and back part to allow assembly and to ensure a non-drip application, have been developed separately. Decisions for final concept selection were made with the company of commission, with data regarding costs, usage interpreted from prototypes and verdicts from external experts within plastics production.

    Sub solutions mentioned, were combined into a final concept which reduces costs and fulfils demands regarding performance, appearance and usability. The material from the project is propositioned to form the basis for further development and testing to ensure high product quality representing CEJN.

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  • 257.
    Kedbäck, Miranda
    University of Skövde, School of Engineering Science.
    Exploring Dynamic Complexity in the Symbiosis of Operations and Maintenance Functions: A Simulation-Based Optimisation Study2018Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Maintenance, the process of preserving the condition of the equipment and performance in a production facility, stands for a considerable large cost in the budget of manufacturing organisations and is strongly affected by short-term philosophy. Therefore, both the long-term and short-term consequences of maintenance strategies need to be examined and analysed. The aim with this research is to investigate the dynamic complexity between the requirements from operations on the performance of maintenance, to illustrate the challenge of trading long-term and short-term requirements and benefits. These aspects have been studied through system dynamics (SD) modelling, simulation-based optimisation (SBO) and multi-objective optimisation (MOO). In order to illustrate the analysed problems, a state-of-the-art literature review has been created and two different scenarios have been evaluated. The scenarios are to investigate both the effects of more or less planned maintenance and the implication of a stock-and-flow structure for hiring and retirements of maintenance resources. A conceptual base model, created in previous research, has been applied and developed in order to meet the objectives.

    From the performed experiments, it can be confirmed that with the use of SD simulation trends and consequences over longer periods of time are truly visualised. In the first scenario, the results indicate that a short-term maintenance management strategy is unprofitable over time. The simulation also reveals that improvement strategies and proactive work can revolutionise capability and profit over time, even if these strategies initially generate a higher cost. In the second scenario, where the effects of a major retirement are visualised, the results confirm that the company needs to act proactively in order to avoid great financial losses. Employee and average skill losses cause long-term negative effects on the capability and availability. The optimisation that has been performed, with the hiring rate as the main variable and the objectives of maximising availability, minimising the direct cost and minimising the indirect cost, has generated feasible solutions on the Pareto front.

    In conclusion, the results from the experiments identify the behaviours and causal relationships in a maintenance system in symbiosis with operations. With the long-term goal of generating less reactive workload on the maintenance function, there are many benefits to obtain. The charted delays and causal relationships in the system indicate multi-level consequences, where a management approach should benefit financially from emphasising the importance of acting proactively and directing resources to improvement strategy work.

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  • 258.
    Kedbäck, Miranda
    et al.
    University of Skövde, School of Engineering Science.
    Ekdahl, Stellan
    University of Skövde, School of Engineering Science.
    Arbetsstandard, tidsunderlag och förbättringsarbete vid manuella arbetsstationer2016Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Brodit AB is a company located in Karlsborg, which manufactures holders for technical communication devices for mounting in vehicles. The manual manufacturing, where bending and assembly takes place, lacks a method for standardisation, a base for time scheduling, a base for manpower planning and a method for continuous improvements. The aim of this bachelor thesis was to develop a base for standardised work, time scheduling and manpower planning as well as a method for continuous improvements. To reach these aims a number of sub targets needed to be reached, which were to sustain an analysis of the current situation through observations and time studies, develop standard data for work tasks, divide the tasks into value adding work, non-value adding work and necessary non-value adding work, develop a suggestion to an improved work standard and develop a method for continuous improvements.

    To reinforce choices of methods and conclusions, a number of engineering areas have been studied. Based on the theoretical frame of references, a number of methods for the empirical study were formed.  The study was conducted of observations according to genchi genbutsu, grouping of work tasks, time motion studies performed with a time watch and SAM analysis, calculation of standard data times, evaluation of value adding-, non-value adding- and necessary non-value adding work, SMED analysis and spaghetti diagrams.

    The result of the empirical study was a base for time scheduling with calculated standard times for each work task, where every work task was evaluated as value adding, non-value adding or necessary non-value adding. Based on this, a base for manpower planning can be compiled. The compilation of standard data times as well as the SAM analysis resulted in cycle times far shorter than the cycle times measured in current production. Also, the setup times appeared to be long and irregular with several unnecessary work tasks performed. The result of the spaghetti diagrams also shows unnecessary movements. The conclusion of this is that non-value adding work tasks occurs in the process, that the work is performed in different ways which causes waste in the process and that the work performance rating is below 100 %. With a standardised way of work as well as eliminated non-value adding work tasks, the production could be increased with 60 %; alternatively, the manpower could be decreased with two workers. With the compiled improvement suggestions implemented, the cycle time at the bending working stations could be decreased with at least 50 % and the total setup time could be decreased with at least 57 %.

    A method for continuous improvements has been developed, based on a PDCA cycle. With improved conditions on each working station and a standardised way to work, possible improvements can be achieved in reduced setup times, reduced cycle times as well as the implementation of a culture of continuous improvements. 

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  • 259.
    Keyvani, Ali
    et al.
    Product and Production Development Dep., Chalmers University of Technology, Gothenburg, Sweden.
    Högberg, Dan
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Hanson, Lars
    Industrial Development, Scania CV, Södertälje, Sweden.
    Lämkull, Dan
    Virtual Methods & IT, Volvo Car Corporation, Gothenburg, Sweden.
    Delfs, Niclas
    Fraunhofer Chalmers Research Centre, Gothenburg, Sweden.
    Rhen, Ida-Märta
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Örtengren, Roland
    Product and Production Development Dep., Chalmers University of Technology, Gothenburg, Sweden.
    Ergonomic Risk Assessment of a Manikin’s Wrist Movements - a Test Study in Manual Assembly2013Conference paper (Refereed)
    Abstract [en]

    Use of digital human modeling (DHM) tools enables early assessment of ergonomic risks in the production development process. This early risk assessment can indicate needs for preventive actions in order to decrease risks for work-related musculoskeletal disorders. A method for the assessment of physical workload has been developed, for the analysis of wrist joint data produced by a DHM tool. The method is tested in a simulation model of an actual manual assembly station in industry where it is assumed that physical workload problems exist. The results show that the method can be successfully applied on an industrial case. In addition, presumptive risks and possible diagnoses are predicted based on the similarity of the simulated task’s motions with motions from other known work class profiles stored in a database based on epidemiological research.

  • 260.
    Khaki Boukani, Farzad
    University of Skövde.
    Overcoming logistical problems in organizations: The case of Elicom AB2007Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper presents an empirical case study of the company Elicom AB. Elicom AB is producing electrical devices that are mostly used in the telecom market where the main customers are. The data that was collected from this case was collected through observations, interviews and the study of company documents. This allowed the author to compare secondary and primary data, as well as quantitative and qualitative information. The problem, the company is facing in the logistical field, was discovered in the labeling production process.

    The production of the labels is unnecessarily complicated and inefficient due to incompatibility of the computer systems. Therefore some parts of the label design have to be made manually, even though the company has a scanning system. When analyzing the problem in detail it became clear to the author that it could be fixed easily and fast and that the key individuals involved in the process already knew the answer to the problem. Therefore the question of the underlying cause of the problem arose. Why has the company not yet fixed the problem if it is so obvious and also everybody in the organization is aware of it?

    When further reanalyzing the problem, the author discovered a second problem, which was not lying in the logistics of the production process, but had its roots in the organizational structure. The problem of interfering authorities and responsibilities made it impossible for the company to overcome the changes needed to solve the logistical problem in the labeling production process. Therefore this problem must be addressed first, together with overcoming the obstacles to change in the organization, to make a problem-solving-process in the logistical area possible.

    In general this paper shows the interrelation of logistics with organization and the highly complex environment manufacturing companies are facing when it comes to changes in the production process.

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  • 261.
    Kjellén, Linus
    et al.
    University of Skövde, School of Engineering Science.
    Björnell, Jonna
    University of Skövde, School of Engineering Science.
    Ställtids- och kassationsreducering, svarvning2016Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Ett examensarbete är utfört på ett tillverkande företag med cirka 140 stycken anställda och utför skärande bearbetning i stål, aluminium och gjutjärn till bland annat bil-, telekom och övrig verkstadsindustri. Produktsortimentet består till största delen av kopplingar till ramlager, medbringare, fyrhjulsdrifter och robotkomponenter. Företaget har en svarvgrupp med tre stycken CNC-svarvar som har problem med långa omställningstider och det upptar en stor del av produktionstiden. Det försvårar för svarvgruppen att leverera produkter i tid, i samband med omställningarna förekommer även en stor mängd kassationer som orsakar kostnader och som även är en bidragande orsak till de långa omställningstiderna.

    Syftet och huvudmålen var att reducera omställningstiden med 30 %, minska kassationer vid omställning med 30 % och att ta fram lämplig metod för ställtidsreducering. För att uppnå syftet och huvudmålen valdes metoden Single Minute Exchange of Die (SMED) som är en metod för att reducera omställningstid. Valet gjordes utifrån en litteraturstudie där metoden visat sig vara resultatrik i liknande fallstudier.

    Med användning av videodokumentation, spagettidiagram och kassationsdokument kunde nuläget fastställas i svarvgruppen. Orsakerna till den långa omställningstiden och kassationerna varierade, en stor anledning till deras långa omställningstider var att de genomförde alla aktiviteter under den inre omställningen. En annan anledning var att svarvgruppen saknade ett standardiserat arbetssätt samt struktur och framförhållning i arbetet.

    Utifrån nulägesanalysen utvecklades förbättringsförslag som implementerades inför en pilotstudie som kunde frambringa ett resultat. Omställningen kunde reduceras med 38 % och kassationer i samband med omställning reducerades med 50 %. Resultatet av studien visar även att metoden är lämplig för fortsatt arbete med ställtidsreducering för svarvgruppen. Genom implementering av SMED metoden har omställningstiden och kassationerna reducerats, vilket medför en ökad flexibilitet eftersom det finns en större förmåga att snabbt genomföra en omställning från en produkt till en annan och snabbare bemöta kundernas efterfrågan.

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  • 262.
    Klarin, Johanna
    et al.
    University of Skövde, School of Engineering Science.
    Johansson, Alexander
    University of Skövde, School of Engineering Science.
    Utveckling av en moduluppbyggd destinationsskylt2015Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A modular destination sign for buses was developed. The work was performed at the University of Skövde in cooperation with the company Mobitec AB that for instance sells the signs that was currently used in the city buses in London. The sign that was developed was meant to serve as a replacement for the signs with printed blinds that were existing in the London city buses. The sign therefore had to live up to the demands on the resolution and readability. This would be achieved by building up the sign with a modular system of Superfine Pitch LED Matrix Card.

     

    The modular system needed to sustain vibrations from the bus and allow individual modules to be easily assembled and disassembled. To develop a functioning system guidelines for DFA and DFD was used, and user needs from installers and repairers were investigated. During the concept generation set-based concurrent engineering was used to avoid further development of non-functioning concept at the expense of elimination of good concepts.

     

    Three remaining, equivalent concepts were modeled and tested for vibration by doing simulations in Creo Parametric 2.0. The vibrations were also tested on 3D-printed models from CAD files. The results showed that all the solutions managed the vibrations. The final concept selection was made by matrices and by usability testing.

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    Utveckling av en moduluppbyggd destinationsskylt
  • 263.
    Korpi, Mika
    et al.
    University of Skövde, School of Technology and Society.
    Karlsson, Sandra
    University of Skövde, School of Technology and Society.
    Drivanordning för bandtransportör: En förstudie till en modulbaserad drivsektion2013Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Kellve manufactures conveyors for bulk and material handling and the company offers specific solutions according to customer preferences. The conveyor typically consists of a drive section, truss frame and safety equipment. The purpose of the thesis is to create a concept for a new modularized drive section in order to be able to continue offering customers the same range of options as before, but with fewer parts. The number of variations of the drive section Kellve offers their customers are identified and presented. The new drive section concept is visualized by a CAD model and a strength analysis is performed. The strength analysis is done using the finite element method and it is performed on both the concept and a basic drive section, which is a standard model of a drive section from Kellve, to ensure that the modifications made to the drive section do not lead to deterioration in strength in comparison with the basic drive section.

    A general introduction to corporate environmental awareness, environmental responsibility, codes of conduct and social responsibility is presented with a description of methods of how a company can promote sustainable development.

    A feasibility study is conducted giving a theoretical background on topics relevant to the thesis. A report of different product development stages, modularization and how these tools are implemented in a product is given followed by a description of the finite element method.

    In order to fully understand the current status of the company’s drive sections the thesis will begin with a study of a typical drive section. Drawings, dialogue and meetings with supervisors at the company are used as background material to fully comprehend the situation. After a status report is created, groundwork for concept generation phase begins, which consists of customer needs identification and development and definition of concept requirements. The work continues with efforts to identify the module drivers and is followed by brainstorming sessions to generate concepts. A number of concepts are selected using a concept selection matrix. The chosen concepts are presented to the company and after discussions the "winning" concept is chosen. The concept includes modularization and vertical assembly/disassembly of the drive pulley in order to achieve a more ergonomic working position during maintenance work.

    The concept and basic drive section are modeled and analyzed in Pro/ENGINEER. The purpose of this analysis is to compare the strength of the basic drive section with the new concept. The drive section is compared in an operational mode and a service mode.

    The outcome of the thesis is that a modularization of the drive section is achieved by maintaining its height regardless of the size of the drive pulley. The sides of the drive section are also combined with bearing plates, which are adapted depending on the size and type of bearing that is used. The bearing plate is no longer dependent on the drive pulley diameter. A modularization of the belt cleaner is conducted by constructing a plate that has distinct holes for each drive pulley diameter.

    With effective stress concentrations surpassing the yield limit, the result of the strength analysis reveals weaknesses in the basic drive section in operational mode as well as service mode. The concept section drive shows very low stress concentrations in operational mode and low effective stress levels not exceeding half of the yield limit in service mode. The recommendation is to evaluate the validity of the input data in the analysis, redesign the basic drive section and conduct new, more accurate analyzes. Furthermore, the modularization work should continue.

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  • 264.
    Koskenranta, Mikael
    University of Skövde, School of Technology and Society. University of Skövde, School of Engineering Science.
    Optimisation of ceiling attachment for AVPOS using FEA2015Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    In product manufacture and assembly it is important to lower materials usage and assembly timewhile retaining a safety margin against structural failure. In this project the ceiling attachment of theAVPOS offloading arm is redesigned based on objectives identified by Löfs Specialmaskiner. Theoriginal ceiling attachment is analysed using finite element analysis to identify any structuralweaknesses to be addressed during redesign. Based on information gained during the FEA threeconcepts are generated and rated based on their estimated assembly times, material usage, partscount and the cutting length for machining.One concept is selected for further topology optimisation and iterative FEA, where material isremoved from the selected concept design while maintaining safety objectives. The optimised designdeveloped during this project is shown to have a lower number of parts, lower usage of material andassembly time while retaining an overall FOS value of 4.In addition to redesigning the ceiling attachment, alternative bearings are also investigated whichchanges the existing ball bearings to a self-aligning sliding bearing with self-lubricating properties,lowering the machining tolerances as well as lowering the needs for service.This project contributes to lowering material usage and ease of assembly in the product AVPOS thatis manufactured by Löfs Specialmaskiner. The redesigned ceiling attachment along with thesuggested bearings will likely simplify future manufacturing as well as lower any concerns for damageto people and property as a result of structural failure.

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    Optimisation of ceiling attachment for AVPOS using FEA
  • 265.
    Kourentzes, Nikolaos
    Department of Management Science, Lancaster University Management School, Lancaster, Lancashire, United Kingdom.
    Intermittent demand forecasts with neural networks2013In: International Journal of Production Economics, ISSN 0925-5273, E-ISSN 1873-7579, Vol. 143, no 1, p. 198-206Article in journal (Refereed)
    Abstract [en]

    Intermittent demand appears when demand events occur only sporadically. Typically such time series have few observations making intermittent demand forecasting challenging. Forecast errors can be costly in terms of unmet demand or obsolescent stock. Intermittent demand forecasting has been addressed using established forecasting methods, including simple moving averages, exponential smoothing and Croston's method with its variants. This study proposes a neural network (NN) methodology to forecast intermittent time series. These NNs are used to provide dynamic demand rate forecasts, which do not assume constant demand rate in the future and can capture interactions between the non-zero demand and the inter-arrival rate of demand events. This overcomes the limitations of Croston's method. In order to mitigate the issue of limited fitting sample, which is common in intermittent demand, the proposed models use regularised training and median ensembles over multiple training initialisations to produce robust forecasts. The NNs are evaluated against established benchmarks using both forecasting accuracy and inventory metrics. The findings of forecasting and inventory metrics are conflicting. While NNs achieved poor forecasting accuracy and bias, all NN variants achieved higher service levels than the best performing Croston's method variant, without requiring analogous increases in stock holding volume. Therefore, NNs are found to be effective for intermittent demand applications. This study provides further arguments and evidence against the use of conventional forecasting accuracy metrics to evaluate forecasting methods for intermittent demand, concluding that attention to inventory metrics is desirable. 

  • 266.
    Kourentzes, Nikolaos
    Department of Management Science, Lancaster University Management School, Lancaster, Lancashire, United Kingdom.
    On intermittent demand model optimisation and selection2014In: International Journal of Production Economics, ISSN 0925-5273, E-ISSN 1873-7579, Vol. 156, p. 180-190Article in journal (Refereed)
    Abstract [en]

    Intermittent demand time series involve items that are requested infrequently, resulting in sporadic demand. Crostons method and its variants have been proposed in the literature to address this forecasting problem. Recently other novel methods have appeared. Although the literature provides guidance on the suggested range for model parameters, a consistent and valid optimisation methodology is lacking. Growing evidence in the literature points against the use of conventional accuracy error metrics for model evaluation for intermittent demand time series. Consequently these may be inappropriate for parameter or model selection. This paper contributes to the discussion by evaluating a series of conventional time series error metrics, along with two novel ones for parameter optimisation for intermittent demand methods. The proposed metrics are found to not only perform best, but also provide consistent parameters with the literature, in contrast to conventional metrics. Furthermore, this work validates that employing different parameters for smoothing the non-zero demand and the inter-demand intervals of Crostons method and its variants is beneficial. The evaluated error metrics are considered for automatic model selection for each time series. Although they are found to perform similar to theory driven model selection schemes, they fail to outperform single models substantially. These findings are validated using both out-of-sample forecast evaluation and inventory simulations. 

  • 267.
    Kourentzes, Nikolaos
    et al.
    Lancaster University Management School, University of Lancaster, Lancaster, United Kingdom.
    Li, Dong
    The York Management School, University of York, York, United Kingdom.
    Strauss, Arne K.
    Warwick Business School, University of Warwick, Coventry, United Kingdom.
    Unconstraining methods for revenue management systems under small demand2019In: Journal of Revenue and Pricing Management, ISSN 1476-6930, E-ISSN 1477-657X, Vol. 18, no 1, p. 27-41Article in journal (Refereed)
    Abstract [en]

    Sales data often only represent a part of the demand for a service product owing to constraints such as capacity or booking limits. Unconstraining methods are concerned with estimating the true demand from such constrained sales data. This paper addresses the frequently encountered situation of observing only a few sales events at the individual product level and proposes variants of small demand forecasting methods to be used for unconstraining. The usual procedure is to aggregate data; however, in that case we lose information on when restrictions were imposed or lifted within a given booking profile. Our proposed methods exploit this information and are able to approximate convex, concave or homogeneous booking curves. Furthermore, they are numerically robust due to our proposed group-based parameter optimization. Empirical results on accuracy and revenue performance based on data from a major car rental company indicate revenue improvements over a best practice benchmark by statistically significant 0.5–1.4% in typical scenarios.

  • 268.
    Kourentzes, Nikolaos
    et al.
    Lancaster University Management School Department of Management Science, Lancaster, United Kingdom.
    Rostami-Tabar, Bahman
    Cardiff Business School, Cardiff University, Cardiff, United Kingdom.
    Barrow, Devon K.
    School of Strategy and Leadership, Faculty of Business and Law Coventry University, Coventry, West Midlands, United Kingdom.
    Demand forecasting by temporal aggregation: Using optimal or multiple aggregation levels?2017In: Journal of Business Research, ISSN 0148-2963, E-ISSN 1873-7978, Vol. 78, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Recent advances have demonstrated the benefits of temporal aggregation for demand forecasting, including increased accuracy, improved stock control and reduced modelling uncertainty. With temporal aggregation a series is transformed, strengthening or attenuating different elements and thereby enabling better identification of the time series structure. Two different schools of thought have emerged. The first focuses on identifying a single optimal temporal aggregation level at which a forecasting model maximises its accuracy. In contrast, the second approach fits multiple models at multiple levels, each capable of capturing different features of the data. Both approaches have their merits, but so far they have been investigated in isolation. We compare and contrast them from a theoretical and an empirical perspective, discussing the merits of each, comparing the realised accuracy gains under different experimental setups, as well as the implications for business practice. We provide suggestions when to use each for maximising demand forecasting gains. 

  • 269.
    Krantz, Johan
    et al.
    University of Skövde, School of Engineering Science.
    Krantz, Stefan
    University of Skövde, School of Engineering Science.
    Förslag på utformning av Kitt- och Sekvensering inför nästa generations motor: På Volvo Cars i Skövde2016Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Volvo Cars Skövde will in year 2018 implement a new engine model in Skövde plant, which will lead to a greatly increased variety of the articles in the material facade at the production line when the engine variants increases. However, the current material facade will not be able to cope with the future increase of articles. Therefore, design proposals for the handling of the material by using kit- and sequence picking externally from the production line have been proposed. Hence, handling these operations externally may lead to an efficient material flow, but also enables handling more articles when the engine variants increase.

    The main objective of the project was to develop proposals on how workplace design for a kit- and sequence picking station may look like, and how the flow of material should be handled to and from these stations. To implement this, a form of a PDCA-method has been used to structure the work. Relevant literature on the theory and studies in similar areas has been reviewed to gather knowledge in this area. Successful methods used in other studies, i.e. interviews, observations and benchmarking, were also used in this project to collect data.

    The results based on the collected data generated, present different layout suggestions of a kit- and sequence picking station, with regard to quality assurance and efficiency of the picking patterns, ergonomics, reliability of delivery and the total area required for these picking stations. It will also manage the flow of materials to and from these stations that should be handled in an efficient way. Prototype sketches of proposed way of transport and aid for the material handling have been developed for the company, which will be a base for continued work before the implementation of the next generation engine in year 2018. 

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  • 270.
    Kälström, Matilda
    University of Skövde, School of Engineering Science.
    UTVECKLING AV EXKLUSIV KLÄDKAMMARE OCH FÖRVARINGSLÖSNING FÖR PRIVATHEM2015Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Design Engineering student Matilda Kälström has developed a range of storage solutions for walk-in closets where the target group for the project is the company’s existing customer base. During the project a basic feasibility study was done to determine the project requirements, identify competitors and find out what demands and requests the customers have. Example of demand was that the product should provide an overview of the content of the walk-in-closet. A literature study was done to gather information about storage, man's relationship to its home and architecture. Identified information was that it's very important for the human to be able to design their home according to their needs and a good guideline to structure storage is to place the clothes according to where on the body they are used.

    A central part of the project is Kansei engineering, which is a concept of connecting peoples’ perceptions to products' design. It has been used in surveys to find out what the customers want to experience, it has been used for idea generation and it has been used to find out if the results gave desirable experiences. The survey results revealed that desirable experiences of a walk-in closet is luxurious, classic, stylish and comfortable. The meaning of these words were used from the National Encyclopedia to make mood boards which then were used to generate ideas.

    The development of ideas were made in three stages with different methods. After each stages the concepts were evaluated and the results were used in the next stage. The methods that were used was for example personas, scenarios, function trees and morphological table. The evaluations was performed with the company, the method PNI and a weighting matrix.

    The result is a collection of twelve modules that customers can combine in their own way of walk-in closets. Four different cabinet modules, two different “storage islands”, two seats, a dressing table, a chest of drawers for jewelries, a shoe rack and a mirror shelf. To finally find out if the result gives the perceptions and experiences that is desirable an evaluation was done with twelve people, mostly students at the University of Skövde. Two different mounting of the modules in the form of a "female" and "male" walk-in-closets were shown. With their own words they were about to describe what impressions they had of the pictures and tell what they thought of these walk-in-closets. The participants' response strengthened the project's results and confirmed that the impressions and experiences were desirable. 

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  • 271.
    Kärmander, Adam
    et al.
    University of Skövde, School of Engineering Science.
    Nori, Daniel
    University of Skövde, School of Engineering Science.
    Produktionstekniskt förbättringsarbete hos Dava Foods: Förbättrande av en maskin2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Detta examensarbete har utförts på Dava Foods i Skara. Det är ett företag där hönsägg i olika kvaliteter bearbetas. Där finns en äggknäckningsprocess som består av två maskiner. Organisationen har problem med maskinen som har till uppgift att separera brickor och ägg. Den stannar alltför ofta och därför har företaget bett om hjälp.

    Syftet med arbetet var att ta reda på vilka orsaker som ligger bakom stoppen och att ge förbättringsförslag för att förhindra framtida oönskade stopp. Observationer och intervjuer genomfördes för att få en bättre förståelse för hur maskinen fungerar. Därefter utfördes fyra stopptidsanalyser för att dokumentera stilleståndstider och för att det skulle vara möjligt att se vad som får maskinen att stanna. Metoden 5 x varför användes för att hitta rotorsakerna till problemen. Förbättringsförslag gavs utifrån de rotorsaker som identifierades och även utifrån egna tankar och idéer. Dessa förslag placerades även in i två PICK-charts så att organisationen eventuellt kan välja att implementera några av dessa i framtiden.

    Arbetet resulterade i 12 unika förbättringsförslag. 2 av dessa hade med brickornas material att göra. Det ena förslaget innebar att endast använda plastbrickor och det andra var en blandning av plast- och pappersbrickor. Ytterligare ett förslag var brickor med 5x5 ägg, vilket innebär att brickan ska ha plats för 5 ägg på bredden och 5 på längden. Tre förbättringsförslag hade med människor att göra. Dessa handlade om att operatören ska försöka vara mer noggrann med avståndet mellan brickor på första rullbandet, att människor ska vara försiktiga vid transport och hantering av äggen samt att det ska vara tre personer som arbetar vid maskinen. Några mer omfattande förbättringsförslag var ett längre första rullband, en robot vid första rullbandet, en bättre funktion som separerar brickor, en ny maskin och en annan layout. Det föreslogs även att minska hastigheten på den så kallade cylindern.

    Slutsatsen är att det finns tre förbättringsförslag som verkligen bör övervägas. Dessa är användning av plastbrickor istället för pappersbrickor, införskaffande av en ny maskin samt tre personer som arbetar vid maskinen. Om plastbrickor används istället för pappersbrickor så hade det blivit mycket mindre stopp. Detta gäller även för en ny maskin som kan hantera både plast- och pappersbrickor. Om tre personer arbetar vid maskinen så kan den tredje personen ha som arbetsuppgift att upptäcka och åtgärda fel innan dessa får maskinen att stanna.

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  • 272.
    Kärrlander, Daniel
    et al.
    University of Skövde, School of Engineering Science.
    Nordström, Marcus
    University of Skövde, School of Engineering Science.
    Utveckling av fiberoptisk ljusgenomföring för lägenhetsdörr2017Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This is a report which covers the bachelor degree project in Product Design Engineering at University of Skövde. The project is conducted in cooperation witha company that manufactures doors and wants to expand their accessory rangewith a product in the market segment between windows and LED-lights toilluminate the very entrance of an apartment and provide the user with sufficientlight. The development process for this product began with a comprehensiveprestudy followed by identification of relevant environments, collection of targetdata through measurements of illumination, and theoretical calculations ofproduct geometries such as light collecting area. The combined knowledge led toa generation stage, evaluation stage and prototype production. The result becamesubstandard and did not reach the desired lighting effect with the identifiedboundary conditions due to unforeseen power losses. If the product is taken outof these boundaries and instead used in more favorable conditions, the result issignificantly better.The conclusion is that passive collection of diffused light is possible but noteffective and above all incompatible with, in this case, high security and demandsfor low costs.

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  • 273.
    Ladrón de Guevara Muñoz, M. Carmen
    et al.
    University of Skövde, School of Engineering Science.
    Martín Márquez, Javier
    University of Skövde, School of Engineering Science.
    Mini-grid system study applied to a stand-alone house located in Málaga, Spain2015Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    A study of an off-grid photovoltaic system for the electrification of a stand-alone single residential house in a rural area located in the city of Málaga, Spain, is presented. The load of an average family house is analysed keeping in mind the available solar energy at this location. A preliminary sizing of the system is carried out considering predefined values for the efficiency of the different technologies employed in the system: photovoltaic (PV) array, batteries as energy storages, inverters to convert the energy obtained from the sun, and diesel gensets to ensure supply under any circumstances. Later, precise brands of the available technologies in the market are selected, and the system is re-sized using the new parameters. The life cycle cost of the mini-grid (MG) system shows that the amortization of the system in 20 years for a stand-alone house is not possible. Although it is not confirmed that 20 years will be sufficient to make the system profitable, other aspects are considered and discussed in terms of their feasibility in Málaga.

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  • 274.
    Lageholm, Joel
    et al.
    University of Skövde, School of Engineering Science.
    Dia, Mohammed
    University of Skövde, School of Engineering Science.
    Hållfasthetsanalys och vidareutveckling av skopa för traktorer med frontlastare2018Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A bucket, designed and constructed by the company Kellfri AB for all-round usage with front-end loader equipped tractors, has been analyzed via finite element analysis in Creo Parametric. Possibilities of mass reduction, suitability in the placement of an additional detail in the upper parts of the bucket and potential strength problems in the construction was investigated. The project was initialized during the prototyping-phase of product development and at the time the bucket was considered to be over dimensioned by the company with regard to their earlier prototype-testing. Static analysis was done for three separate models; The Company’s own CAD-model, for which the strength of the bucket, as it was originally designed, was evaluated. A second model was made for the use of iterative changes in the construction, each followed by an analysis, to test different solutions for reducing the buckets mass without compromising strength and to address strength issues found in the original model. A third model, comprised of a simplified section of the buckets front, was then used to further evaluate and address the most critical of the strength problems that was found. The bucket was, at the end of the project, considered to be inadequately dimensioned for one of the features of the suggested front-end loader model. Suggestions was therefore given, with probable uncertainties accounted for, regarding a suitable area for mass reduction, changes in the design with the possibilities of cost-reduction by simplifying the manufacturing and assembly processes and also actions to be made in regard of strength problems found. Placement of the upper part-detail was considered safe and therefore given a suggested shape.

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  • 275.
    Land, Niklas
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Syberfeldt, Anna
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Almgren, Torgny
    GKN Aerospace Sweden AB, Trollhättan, Sweden.
    Vallhagen, Johan
    Volvo Group Trucks Operations, AB Volvo, Gothenburg, Sweden.
    Virtual Human-Robot Collaboration: The Industry's Perspective on Potential Applications and Benefits2019In: Advances in Manufacturing Technology XXXIII: Proceedings of the 17th International Conference on Manufacturing Research, incorporating the 34th National Conference on Manufacturing Research, September 10–12, 2019, Queen’s University Belfast, UK / [ed] Yan Jin, Mark Price, Amsterdam: IOS Press, 2019, Vol. 9, p. 161-166Conference paper (Refereed)
    Abstract [en]

    Two keystones of Industry 4.0 are the increased use of autonomous robots and advanced simulation software. Human-Robot Collaboration (HRC) combines the strengths of humans and robots, opening up application areas that previously could not be automated. However, the realization of HRC on industrial shop floors is held back by several challenges: safety, trust, the need for intuitive interfaces, and design methods. This study investigates the automotive industry’s perspective on relevant application areas and potential benefits of HRC. The data were collected through a survey of 185 participants from a variety of working roles in the automotive industry. The results of the study indicate that participants from the automotive industry consider that the areas best suited to the implementation of collaborative robots are material handling, assembly, and quality control, with potential benefits in ergonomics, efficiency, and quality. The results can be used for the development of a future virtual HRC simulation model.

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  • 276.
    Larsson, Carina
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Communicating performance measures: Supporting continuous improvement in manufacturing companies2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Manufacturing enterprises are a key driver of economic growth (Eurostat, 2016). Implementing continuous improvement (CI) is commonly used to increase competitiveness (Hyland et al., 2007), but despite the well-known theory of CI, many manufacturing companies fail in implementing it (Bhasin, 2012; Nordin et al., 2012; Tiwari et al., 2007).

    An identified critical success factor in CI implementation is the evaluation of performance, including the performance evaluation system itself, the linkage between targets at different company levels, and continual evaluation of performance (Bakås et al., 2011; Scherrer-Rathje et al., 2009; Ukko et al., 2009). Another critical success factor in CI implementation is the communication of performance measures (Bakås et al., 2011; Ukko et al., 2009).

    This research explores the communication of performance measures. The aim is to support CI by improving the communication of performance measures, and to this end, this thesis concentrates on identifying the main challenges in the communication of performance measures supporting CI. The research scope is manufacturing companies in general, and manufacturing SMEs in particular. The relevant literature concerning the communication of performance measures in manufacturing companies is identified and summarized. Also, current practice is explored, focusing on how performance measures are communicated in manufacturing companies, and whether and how the communication supports CI. This has been done to identify divergences between current practice and theory. Finally, theory and empirical findings are synthesized to identify some of the main challenges to be addressed in order to succeed in CI.

    The main task is to support CI efforts in manufacturing SMEs, eliminating the identified divergences in the communication of performance measures by adapting these measures to these manufacturing SMEs. These challenges can be summarized as follows: 

    - using both financial performance measures as well as objective and subjective, non-financial performance measures  - aligning performance measures with strategy and targets  - integrating all performance measure communication, as related to both daily performance and CI, in the same communication loop.  - forming two-way communication channels between managers and operators  - aligning oral and written communication channels  - exploring how information systems can facilitate the communication of performance measures  - using and optimizing the visual communication of performance measures

  • 277.
    Larsson, Carina
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Jönköping.
    Säfsten, Kristina
    University of Jönköping.
    Visual communication of performance meaures supporting continuous improvement: Challenges and opportunities for manufacturing SMEs2016Conference paper (Refereed)
    Abstract [en]

    This paper provides a holistic view of visual communication of performance measures supporting continuous improvement in manufacturing SMEs. This is done by a theoretical part with a literature review, and an empirical part with case studies, including both the managers’ and the operators’ perspectives, and by focusing on manufacturing SMEs. The paper identifies five challenges and one opportunity in visual communication that SMEs perceive when using visual communication of performance measures, supporting continuous improvement.

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  • 278.
    Larsson, Carina
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. School of Engineering, Jönköping University.
    Säfsten, Kristina
    School of Engineering, Jönköping University.
    Syberfeldt, Anna
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Performance measurement communication supporting lean production in SMEs2014In: Performance management: Designing the high-performing organization, 2014, p. 714-725Conference paper (Refereed)
    Abstract [en]

    Purpose

    The aim of this paper is to provide an overview of the current status of performance measurement communication to support lean production in SMEs.

    Design/methodology/approach

    The paper is based on theoretical and empirical studies. A literature review of existing research in performance measurement communication, focusing on lean production in SMEs, was carried out. The empirical part is based on interviews with both managers and operators in SMEs in the south of Sweden working with lean production. Twenty-four interviews in eight companies / plants were carried out.

    Findings

    The paper provides a structured overview of current research in performance measurement communication. Performance measurement communication was categorised into three parts, which taken together could support lean production implementation in SMEs. It can be concluded that, although all existing research in performance measurement and communication, there is no operational guideline of how to communicate performance measurement. From the interviews it can be seen that the companies have improved their performance measurement communication during the lean production implementation, but that there is no common way of communicating performance measurements in SMEs.

  • 279.
    Larsson, Carina
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Säfsten, Kristina
    Högskolan i Jönköping.
    Syberfeldt, Anna
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Performance measurement follow-up supporting continuous improvements in manufacturing companies: a systematic review2015In: 22nd EurOMA conference: Operations management for sustainable competitiveness / [ed] Gerald Reiner, 2015Conference paper (Refereed)
    Abstract [en]

    Performance measurement has been paid a lot of attention. This paper provides a systematic review of existing research in performance measurement follow-up, which so far has been less treated. The paper suggests a categorization of the follow-up phase into the performance measurement system, input to and output from the system, and operational activities. It is concluded that there is a lack of research concerning the operational activities in the follow-up phase. It is also concluded that most of the research concerning follow-up of performance measurement does not support continuous improvement explicitly, but concerns performance measurement follow-up in general.

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  • 280.
    Leffler, Karin
    University of Skövde, School of Technology and Society.
    Shear Behaviour of Adhesive Layers2005Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    An experimental method to determine the complete stress versus deformation relation for a thin adhesive layer loaded in shear is presented. The work is based on a classical specimen geometry, i.e. the end-notch flexure specimen (ENF-specimen) and the experiments are evaluated based on an inverse method. By studying the energy balance at the crack tip an expression for the energy release rate is derived. The theory considers the effects of a flexible adhesive layer and is based on beam theory. From the energy release rate the stress-deformation relation is derived using the inverse method.

    Quasi-static experiments are performed using a servo-hydraulic testing machine. The deformation process at the crack tip is monitored during the experiments by use of a CCD-camera attached to a microscope. The method requires differentiation of the energy-deformation relation, therefore a Monte-Carlo simulation is performed to investigate how small errors in the data acquisition system affects the final stress-deformation relation. Small errors in the measurement of the force and shear deformation give small effects on the final stress-deformation relation.

    Experiments on three different geometries of the specimen are performed. The experiments give consistent results. It is shown that if the process zone in front of the crack tip is large, then the stress-deformation relation does not depend on the dimensions of the adherends. Thus, the constitutive relation can be considered to be a property of the adhesive layer.

  • 281.
    Lidberg, Simon
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Volvo Car Corporation, Sweden.
    Aslam, Tehseen
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Pehrsson, Leif
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Evaluating the impact of changes on a global supply chain using an iterative approach in a proof-of-concept model2018In: Advances in Manufacturing Technology XXXII: Proceedings of the 16th International Conference on Manufacturing Research, incorporating the 33rd National Conference on Manufacturing Research, September 11–13, 2018, University of Skövde, Sweden / [ed] Peter Thorvald, Keith Case, Amsterdam: IOS Press, 2018, p. 467-472Conference paper (Refereed)
    Abstract [en]

    Analyzing networks of supply-chains, where each chain is comprised of several actors with different purposes and performance measures, is a difficult task. There exists a large potential in optimizing supply-chains for many companies and therefore the supply-chain optimization problem is of great interest to study. To be able to optimize the supply-chain on a global scale, fast models are needed to reduce computational time. Previous research has been made into the aggregation of factories, but the technique has not been tested against supply-chain problems. When evaluating the configuration of factories and their inter-transportation on a global scale, new insights can be gained about which parameters are important and how the aggregation fits to a supply-chain problem. The paper presents an interactive proof-of-concept model enabling testing of supply chain concepts by users and decision makers.

  • 282.
    Lidberg, Simon
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Aslam, Tehseen
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Pehrsson, Leif
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Optimizing real-world factory flows using aggregated discrete event simulation modelling: Creating decision-support through simulation-based optimization and knowledge-extraction2019In: Flexible Services and Manufacturing Journal, ISSN 1936-6582, E-ISSN 1936-6590Article in journal (Refereed)
    Abstract [en]

    Reacting quickly to changing market demands and new variants by improving and adapting industrial systems is an important business advantage. Changes to systems are costly; especially when those systems are already in place. Resources invested should be targeted so that the results of the improvements are maximized. One method allowing this is the combination of discrete event simulation, aggregated models, multi-objective optimization, and data-mining shown in this article. A real-world optimization case study of an industrial problem is conducted resulting in lowering the storage levels, reducing lead time, and lowering batch sizes, showing the potential of optimizing on the factory level. Furthermore, a base for decision-support is presented, generating clusters from the optimization results. These clusters are then used as targets for a decision tree algorithm, creating rules for reaching different solutions for a decision-maker to choose from. Thereby allowing decisions to be driven by data, and not by intuition. 

  • 283.
    Lidberg, Simon
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Volvo Car Corporation, Skövde, Sweden.
    Pehrsson, Leif
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Frantzén, Marcus
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Applying Aggregated Line Modeling Techniques to Optimize Real World Manufacturing Systems2018In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 89-96Article in journal (Refereed)
    Abstract [en]

    The application of discrete event simulation methodology in the analysis of higher level manufacturing systems has been limited due to model complexity and the lack of aggregation techniques for manufacturing lines. Recent research has introduced new aggregation methods preparing for new approaches in the analysis of higher level manufacturing systems or networks. In this paper one of the new aggregated line modeling techniques is successfully applied on a real world manufacturing system, solving a real-world problem. The results demonstrate that the aggregation technique is adequate to be applied in plant wide models. Furthermore, in this particular case, there is a potential to reduce storage levels by over 25 %, through leveling the production flow, without compromising deliveries to customers.

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  • 284.
    Lidberg, Simon
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Pehrsson, Leif
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Using Aggregated Discrete Event Simulation Models and Multi-Objective Optimization to Improve Real-World Factories2018In: Proceedings of the 2018 Winter Simulation Conference / [ed] M. Rabe, A. A. Juan, N. Mustafee, A. Skoogh, S. Jain, B. Johansson, IEEE, 2018, p. 2015-2024Conference paper (Refereed)
    Abstract [en]

    Improving production line performance and identifying bottlenecks using simulation-based optimization has been shown to be an effective approach. Nevertheless, for larger production systems which are consisted of multiple production lines, using simulation-based optimization can be too computationally expensive, due to the complexity of the models. Previous research has shown promising techniques for aggregating production line data into computationally efficient modules, which enables the simulation of higher-level systems, i.e., factories. This paper shows how a real-world factory flow can be optimized by applying the previously mentioned aggregation techniques in combination with multi-objective optimization using an experimental approach. The particular case studied in this paper reveals potential reductions of storage levels by over 30 %, lead time reductions by 67 %, and batch sizes reduced by more than 50 % while maintaining the delivery precision of the industrial system.

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  • 285.
    Lind, Carl Mikael
    et al.
    Unit of Occupational Medicine, Karolinska Institutet, Stockholm, Sweden / Division of Ergonomics, KTH Royal Institute of Technology, Huddinge, Sweden.
    Sandsjö, Leif
    Faculty of Caring Science, Work Life and Social Welfare, University of Borås, Sweden / Design & Human Factors, Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Mahdavian, Nafise
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Hanson, Lars
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Scania CV, Södertälje, Sweden.
    Olivares, Jozé Antonio Diaz
    Division of Ergonomics, KTH Royal Institute of Technology, Huddinge, Sweden.
    Yang, Liyun
    Unit of Occupational Medicine, Karolinska Institutet, Stockholm, Sweden / Division of Ergonomics, KTH Royal Institute of Technology, Huddinge, Sweden.
    Forsman, Mikael
    Unit of Occupational Medicine, Karolinska Institutet, Stockholm, Sweden / Division of Ergonomics, KTH Royal Institute of Technology, Huddinge, Sweden.
    Prevention of Work: Related Musculoskeletal Disorders Using Smart Workwear – The Smart Workwear Consortium2019In: Human Systems Engineering and Design: Proceedings of the 1st International Conference on Human Systems Engineering and Design (IHSED2018): Future Trends and Applications, October 25-27, 2018, CHU-Université de Reims Champagne-Ardenne, France / [ed] Tareq Ahram, Waldemar Karwowski, Redha Taiar, Springer, 2019, Vol. 876, p. 477-483Conference paper (Refereed)
    Abstract [en]

    Adverse work-related physical exposures such as repetitive movements and awkward postures have negative health effects and lead to large financial costs. To address these problems, a multi-disciplinary consortium was formed with the aim of developing an ambulatory system for recording and analyzing risks for musculoskeletal disorders utilizing textile integrated sensors as part of the regular workwear. This paper presents the consortium, the Smart Workwear System, and a case study illustrating its potential to decrease adverse biomechanical exposure by promoting improved work technique. 

  • 286.
    Lindell Wallgren, Ida
    University of Skövde, School of Engineering Science.
    Alternativt material i behållare för konstgödselrampspridare: Förarbete för prototyp2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Överums Bruk AB manufactures agricultural equipment such as the fertilizer spreader Wing Jet. Wing Jet has a container which today is manufactured from stainless steel and the company wishes to know if it is possible and suitable to manufacture the container from plastic/plastic composite with the purpose to lessen the containers production costs and weight. This work is limited to the container, the rest of the fertilizer spreader should not need any changes to switch the stainless steel container for a plastic/plastic composite one and the work does not include manufacturing a prototype. Rotational molding and hand lay-up (glass-fibre reinforcement) are two manufacturing processes which are suitable to use when manufacturing such large objects. Simulations of a rotational molded container in the material high density polyethylene (HDPE) in the program SolidWorks Simulation Standard results in maximum effective stresses just above the materials tensile strength when a pressure based on equations from the European standard Eurocode 1-4: 2006 (Silos and Tanks) are applied on the containers inside. However, deformations of several centimeters occurs which in itself is not a problem, though it makes the container less esthetically appealing (smooth sides bulges outward). The containers weight decreases to approximately half of that of today and it is cheaper to manufacture. Materials and manufacturing processes which results in a container with higher stiffness in the purpose of lessen the deformation is recommended to investigate as future work. Examples of this are glass-fibre reinforced polyester or epoxy and “sandwich”-constructions. A sandwich-construction is comprised of two (or more) layers of a material with a core, of e.g. foam, between. The simulations carried out are linear elastic, whereas plastics generally are non-linear, so non-linear simulations should be carried out before a prototype in manufactured.

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  • 287.
    Linder, Jonas
    University of Skövde, School of Engineering Science.
    Kyleffektivisering av en havsvattenanläggning: Havets Hus i Lysekil2016Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Havets Hus i Lysekil bedriver en anläggning med ett flertal havsvattenakvarium som innehåller fiskar och havsdjur från svenska havsvatten. Till anläggningen tas det kontinuerligt in nytt havsvatten från Gullmarsfjorden, till några av akva-rierna kyls det inkommande havsvattnet med hjälp av en kylmaskin. I dagsläget är kylmaskinen luftkyld, vilket är ineffek-tivt. Havets Hus vill undersöka möjligheten att effektivisera kylprocessen genom att kyla maskinen mer effektivt, undersö-ka om det går att ta vara på värmeenergin som annars släpps ut i luften eller på något annat sätt göra kylprocessen mer effektiv.Sex alternativ för effektivare kylning har tagits fram. Det finns två inriktningar på alternativen, antingen att förbättra den befintliga installationen genom att till exempel kyla dess kondensor mer effektivt med hjälp utav havsvatten eller att installera nya maskiner. Det finns också ett kompletteringsalternativ som går att kombinera med alla de andra alternativen och går ut på att installera en värmeväxlare mellan ingående havsvatten som ska kylas och utgående havsvatten från de kylda akvarierna. Alternativet som ger störst ekonomisk sparpotential går ut på att installera två nya kylmaskiner. En som är dimensionerad efter Havets Hus varmvattenbehov och som tar värme från det inkommande havsvattnet och en som fyller upp det resterande kylbehovet. De nya maskinerna fyller det totala kylbehovet på Havets Hus, det vill säga både kylbehovet för det inkommande havsvattnet och för ventilationssystemet. Alternativet kan spara Havets Hus ca 184 000-199 000 kr/år och tillsammans med en värmeväxlare kan det spara ca 202 000-223 000 kr/år.

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  • 288.
    Lindström, Adam
    University of Skövde, School of Engineering Science.
    Undersökning av mekanisk belastning på ytmonterade elektriska komponenter vid screentryckning2016Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    A study is done to find out if there is any risk to damage surface mounted components with the use of pneumatic supports during screen printing. The literature review suggests that there is only one type of component that is relevant to analyze: MLCC (multilayered ceramic chip capacitor). It is also pointed out that bending of the PCB (Printed Circuit Board) on which the MLCC is mounted may cause it to crack.

    For the load case that is present during screen printing, the deflection of the PCB is analyzed using two methods: First an analytical method for beam on elastic foundation and second: FEM (Finite Element Method) with discrete springs as support. For these calculations the size of the PCB is set to have the dimensions 100x40x1.6 mm. According to the analytical method the PCBs deflection is 0.6 mm and the FEM 0.7 mm. The difference in deflection is because the analytical method assumes that the elastic foundation is evenly spread while for the FEM the supports are idealized as discrete springs.

    The stress in the MLCC as a result of the PCB bending has been calculated both analytically and with FEM. The analytical solution is based on beam theory and the MLCC is assumed to deform equally to the PCB. In the FEM analysis, the solder joint is also considered. The analytical calculations result in very large stresses within the MLCC (705 MPa) which is due to the assumptions made that the MLCC deforms equally to the PCB. In reality, the solder joint also deforms which dampens the stresses in the MLCC. This is why the FEM analysis gives a more realistic result and the stress is calculated to 37 MPa.

    The conclusion of this study is that the pneumatic supports can be used without risk of damaging surface mounted components.

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  • 289.
    Linero Jiménez, Adriano
    University of Skövde, School of Engineering Science.
    DEVELOPMENT OF A MODEL OF THE DEGRADATION OF THE MECHANICAL PROPERTIES OF POLYOXYMETHYLENE (POM) IN THE PRESENCE OF BIODIESEL2014Independent thesis Advanced level (degree of Master (One Year)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    This project analyses the impact in the mechanical properties of Polyoxymethylene (POM) of three different blends of biodiesels: B0 with 0% of Rapeseed Methyl-ester (RME), B20 with 20% of RME and B100 with 100% of RME. Polyoxymethylene specimens have been subjected to an accelerated aging during 1600 hours at 85ºC. This is the equivalent to 20 years of life time. In addition, a thermal oxidation in air at the same temperature has been performed to check the impact of the temperature in the final degradation.Three different methods have been performed to calculate the diffusion rate, however and one of them has been selected for its reliable results. The second Fick´s law have been chosen to model the diffusion. The diffusion rate has been calculated for the B20 and B100 blend due to the B0 blend has a non-constant diffusion rate. B20 shows also some divergence while B100 fits the Fickian behaviour.A Finite Different approximation method has been used to predict the concentration profiles of the diffusion process of B20 blend. They have been compared with the results of the IR Microscope, with a clear misalignment between the expected and the actual values.Tensile tests have been done in different stages of the test to check the stress-strain behaviour of the specimens for each aging type. The most relevant parameter of degradation is the Elongation At Break (EAB), which decrease considerably a cause of the embrittlement. A study of the real stress-strain has been also done to assure the real behaviour of the material.A fracture surface study through Scanning Electron Microscope (SEM) and Light Microscope has been done to assure the brittle behaviour with the aging and the changes in the structure of the material.The swelling behaviour has been also modelled, and the bases for a future FEM analysis have been exposed.

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  • 290.
    Lingman, Simon
    et al.
    University of Skövde, School of Engineering Science.
    Einemo Swahn, Dennis
    University of Skövde, School of Engineering Science.
    Utveckla förbättringsunderlag och utöka utnyttjandegraden för en maskincell2019Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Detta examensarbete är utfört på RPC Superfos i Mullsjö och företaget tillverkar plastförpackningar till livsmedelsprodukter runtom i världen. RPC Superfos har ett uppsatt mål att det sammanlagda TAK/OEE-värdet för samtliga maskiner inte skall understiga 76,4 %. I dagsläget ligger många av maskincellerna på ett TAK/OEE-värde över målet, medan vissa ligger under 50 % vilket innebär att målet inte uppnås. Den maskincell som omfattas för projektet har lägst TAK/OEE-värde av samtliga maskinceller i fabriken. Syftet har varit att undersöka varför denna maskin inte uppnår företagets mål med ett TAK/OEE värde på 76,4 %. Efter att ha analyserat data över maskincellens stopp konstaterades att den bidragande orsaken till det låga TAK/OEE-värdet beror på ställtiden. Utifrån detta konstaterande har flera arbetsmetoder som frekvensstudier, intervjuer, SMED och spaghettidiagram använts för att presentera förbättringsförslag. Just ställtiden har valts som ett delmål för att fortsätta processen och genom en överenskommelse med företaget valdes att försöka reducera ställtiden från mediantiden 12h till 7h och detta skulle motsvara 42 % av den totala ställtiden på maskincellen. Metodvalen som tidigare nämnts beskrivs i referensramen och detta har gynnat det fortsatta arbetet med att försöka reducera ställtiden och därmed öka tillgängligheten för maskincellen. Under sju omställningar användes Genchi Genbutsu som arbetsmetod för att skapa en ökad förståelse över processen. Under samtliga omställningarsamlades data in med arbetsmetoden frekvensstudie där ställarnas aktiviteter kategoriserades för att identifiera beläggningen för varje aktivitet. Slutligen användes arbetsmetoden spaghettidiagram för att analysera och dokumentera ställarnas rörelser. 19 förbättringsförslag presenterades för personal på RPC Superfos, 10 utav förbättringsförslagen användes under en avslutande omställning. Resultatet från den avslutande omställningen jämfördes emot mediantiden för en omställning. Resultatet blev att omställningen tog 5 timmar, 10 minuter och 14 sekunder, vilket innebär en procentuell minskning av omställningstiden med 57,5%

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  • 291.
    Linnéusson, Gary
    University of Skövde, School of Technology and Society.
    Literature Review on System Dynamics and Simulation2006Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report is a literature review of System Dynamics (SD) and simulation, with enough information so the receiver can form a mental model of his own of what SD is.

    It started in the 1950s by Jay W. Forrester at the Massachusetts Institute of Technology, a devoted man that through his career always sought for practical applications of theory and gained skills. The key in why this new way of approaching problems in complex systems was its strength in capturing the dynamics, through the use of a computer to run a modeled system for a set of time and experimenting on which variables to modify or rearrange. SD methodology uses the theory of information feedbacks (i.e. closed loop structures), and the structure is based on the decision making processes or policies that interrelate in ways in the system. The model is valid if it shows the same dynamic behavior as the real system.

    In the report you will find some history and background to SD and the contents of the methodology, some application areas and two models; of which simulation is performed, one made by Jay Forrester and one very simple made by Gary Linnéusson.

    Main purpose with this review was to find out if SD could serve as a tool for simulating organizational development. If it can, further research on how will be part of a doctoral study project within CAPE, an Industrial Graduate School in Advanced Production Engineering. This due to that Arkivator Falköping AB is interested in to conduct an attendee in that School which would research on: "developing a method that would support management in decisions to develop their organization". The result of this review shows that SD can be a tool to treat that issue, one of very few tools that consider interrelations and interactions within organizational systems.

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  • 292.
    Linnéusson, Gary
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Towards strategic development of maintenance and its effects on production performance: A hybrid simulation-based optimization framework2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Managing maintenance in manufacturing within an economical short-termism framework and taking the consequential long-term cost effects into account is hard. The increasing complexity of managing maintenance and its impact on the business results calls for more advanced methods to support long-term development through effective activities in the production system environment. This problem-based design science research has evolved into the novel concept of a hybrid simulation-based optimization (SBO) framework which integrates multi-objective optimization (MOO) with system dynamics (SD) and discrete-event simulation (DES) respectively. The objective is to support managers in their decision-making on the strategic and operational levels for prioritizing activities to develop maintenance and production performance.

    To exemplify the hybrid SBO framework this research presents an SD model for the study of the dynamic behaviors of maintenance performance and costs, which aims to illuminate insights for the support of the long-term strategic development of maintenance practices. The model promotes a system view of maintenance costs that includes the dynamic consequential costs as the combined result of several interacting maintenance levels throughout the constituent feedback structures. These levels range from the applied combination of maintenance methodologies to the resulting proactiveness in production, such as the ratio between planned and unplanned downtime, in continuous change based on the rate of improvements arising from root-cause analyses of breakdowns. The model creation and validation process have been supported by two large maintenance organizations operating in the Swedish automotive industry. Experimental results show that intended changes can have both short-term and longterm consequences, and that the system may show both obvious and hidden dynamic behavioral effects.

    The application of MOO distinguishes this work from previous research efforts that have mixed SD and DES. It presents a unique methodology to support more quantitative and objective-driven decision making in maintenance management, in which the outcome of an SD+MOO strategy selection process forms the basis for performance improvements on the operations level. This is achieved by framing the potential gains in operations in the DES+MOO study, as a result of the applied strategy in the SD model. All in all, this hybrid SBO framework allows pinpointing maintenance activities based on the analysis of the feedback behavior that generates less reactive load on the maintenance organization.

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  • 293.
    Linnéusson, Gary
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre. Production Engineering and Production Preparation, Arkivator AB, Falköping, Sweden .
    Jägstam, Mats
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Näsström, C.
    Production Engineering and Production Preparation, Arkivator AB, Falköping, Sweden.
    Cutting Tool Management: A Dynamic Assessment of Opportunities for Improvement2008In: Proceedings of the 18th International Conference on Flexible Automation and Intelligent Manufacturing: FAIM 2008 / [ed] Leo J. de Vin, 2008, Vol. 2, p. 1084-1091Conference paper (Refereed)
    Abstract [en]

    Lack of time due to daily problems in need of attention restrains proper assessments of improvement opportunities. There is neither proper support at hand to deal with the dynamic complexity of human activity and systems in use. This paper explores if system dynamics simulation can be used to model tooling problems on a management problem level at a manufacturer and evaluates its use. System dynamics is a methodology designed to aid understanding of dynamically complex problems and increases decision making impact. The results focus on the achieved models which prove to have sense behaviour despite lack of thorough data. In conclusion the applied method provides with an analysis of complex problem situations applicable for a decision support, otherwise performed through good guessing. Main characteristics from reality have been included in model and an experimental laboratory to test future policies on achieved.

  • 294.
    Linnéusson, Gary
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Aslam, Tehseen
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science.
    Investigating Maintenance Performance: A Simulation Study2016In: Proceedings of the 7th Swedish Production Symposium, 2016Conference paper (Refereed)
    Abstract [en]

    Maintenance can be performed in multiple procedures, and it is hard to justify investments in preventive work. It is a complex equation between the inherent complexity of maintenance and its tight dependencies with production, but also the aspect of direct cost and consequential costs from activities. A model is presented that quantify dynamics of maintenance performance in order to enable a systems analysis on the total of consequences from different strategies. Simulation offers experimenting and learning on how performance is generated. The model is based on parts of previous research on maintenance modelling, system dynamics, maintenance theory, and mapping of practical information flows in maintenance. Two experiments are presented that both take off from a reactive strategy of maintenance performance, and implement two different strategies for preventive maintenance. Using the model enriches the analysis on how the aspects of maintenance performance work together with different maintenance strategies.

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    Investigating Maintenance Performance: A Simulation Study
  • 295.
    Linnéusson, Gary
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Aslam, Tehseen
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    A hybrid simulation-based optimization framework for supporting strategic maintenance to improve production performance2020In: European Journal of Operational Research, ISSN 0377-2217, E-ISSN 1872-6860, Vol. 281, no 2, p. 402-414Article in journal (Refereed)
    Abstract [en]

    Managing maintenance and its impact on business results is increasingly complex, calling for more advanced operational research methodologies to address the challenge of sustainable decision-making. This problem-based research has identified a framework of methods to supplement the operations research/management science literature by contributing a hybrid simulation-based optimization framework (HSBOF), extending previously reported research.

    Overall, it is the application of multi-objective optimization (MOO) with system dynamics (SD) and discrete-event simulation (DES) respectively which allows maintenance activities to be pinpointed in the production system based on analyzes generating less reactive work load on the maintenance organization. Therefore, the application of the HSBOF informs practice by a multiphase process, where each phase builds knowledge, starting with exploring feedback behaviors to why certain near-optimal maintenance behaviors arise, forming the basis of potential performance improvements, subsequently optimized using DES+MOO in a standard software, prioritizing the sequence of improvements in the production system for maintenance to implement.

    Studying literature on related hybridizations using optimization the proposed work can be considered novel, being based on SD+MOO industrial cases and their application to a DES+MOO software.

  • 296.
    Linnéusson, Gary
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Aslam, Tehseen
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Justifying Maintenance Studying System Behavior: A Multipurpose Approach Using Multi-objective Optimization2017In: 35th International Conference of the System Dynamics Society 2017: Cambridge, Massachusetts, USA 16 - 20 July 2017 / [ed] J. Sterman, N. Repenning, Curran Associates, Inc., 2017, Vol. 2, p. 1061-1081Conference paper (Refereed)
    Abstract [en]

    Industrial maintenance includes rich internaldynamic complexity on how to deliver value. While the technical development hasprovided with applicable solutions in terms of reliability and condition basedmonitoring, managing maintenance is still an act of balancing, trying to pleasethe short-termism from the economic requirements and simultaneously address thenecessity of strategic and long-term thinking. By presenting an analysis tojustify maintenance studying system behavior, this paper exemplifies thecontribution of the combined approach of a system dynamics maintenanceperformance model and multi-objective optimization. The paper reveals howinsights from the investigation, of the near optimal Pareto-front solutions inthe objective space, can be drawn using visualization of performance ofselected parameters. According to our analysis, there is no return back to thesingle use of system dynamics; the contribution to the analysis of exploringsystem behavior, from applying multi-objective optimization, is extensive.However, for the practical application, the combined approach is not areplacement – but a complement. Where the interpretation of the visualizedPareto-fronts strongly benefits from the understanding of the model dynamics, inwhich important nonlinearities and delays can be revealed, and thus facilitateon the selected strategical path for implementation.

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  • 297.
    Linnéusson, Gary
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Jönköping University, School of Engineering, Sweden.
    Aslam, Tehseen
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Quantitative analysis of a conceptual system dynamics maintenance performance model using multi-objective optimisation2018In: Journal of Simulation, ISSN 1747-7778, E-ISSN 1747-7786, Vol. 12, no 2, p. 171-189Article in journal (Refereed)
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  • 298.
    Linnéusson, Gary
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Jönköping University, Sweden.
    Aslam, Tehseen
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Relating strategic time horizons and proactiveness in equipment maintenance: a simulation-based optimization study2018In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 72, p. 1293-1298Article in journal (Refereed)
    Abstract [en]

    Identifying sustainable strategies to develop maintenance performance within the short-termism framework is indeed challenging. It requires reinforcing long-term capabilities while managing short-term requirements. This study explores differently applied time horizons when optimizing the tradeoff between conflicting objectives, in maintenance performance, which are: maximize availability, minimize maintenance costs, and minimize maintenance consequence costs. The study has applied multi-objective optimization on a maintenance performance system dynamics model that contains feedback structures that explains reactive and proactive maintenance behavior on a general level. The quantified results provide insights on how different time frames are conditional to enable more or less proactive maintenance behavior in servicing production.

  • 299.
    Linnéusson, Gary
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Aslam, Tehseen
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Towards strategic development of maintenance and its effects on production performance by using system dynamics in the automotive industry2018In: International Journal of Production Economics, ISSN 0925-5273, E-ISSN 1873-7579, Vol. 200, p. 151-169Article in journal (Refereed)
    Abstract [en]

    Managing maintenance within an economical short-termism framework, without considering the consequential long-term cost effect, is very common in industry. This research presents a novel conceptual system dynamics model for the study of the dynamic behaviors of maintenance performance and costs, which aims to illuminate insights for the support of the long-term, strategic development of manufacturing maintenance. By novel, we claim the model promotes a system's view of maintenance costs that include its dynamic consequential costs as the combined result of several interacting maintenance levels throughout the constituent feedback structures. These range from the applied combination of maintenance methodologies to the resulting proactiveness in production, which is based on the rate of continuous improvements arising from the root cause analyses of breakdowns. The purpose of using system dynamics is to support the investigations of the causal relationships between strategic initiatives and performance results, and to enable analyses that take into consideration the time delays between different actions, in order to support the sound formulation of policies to develop maintenance and production performances. The model construction and validation process has been supported by two large maintenance organizations operating in the Swedish automotive industry. Experimental results show that intended changes can have both short and long-term consequences, and that obvious and hidden dynamic behavioral effects, which have not been reported in the literature previously, may be in the system. We believe the model can help to illuminate the holistic value of maintenance on the one hand and support its strategic development as well as the organizational transformation into proactiveness on the other.

  • 300.
    Liu, Yu
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Syberfeldt, Anna
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Strand, Mattias
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    A Review of Simulation Based Life Cycle Assessment in Manufacturing Industry2018In: Advances in Manufacturing Technology XXXII: Proceedings of the 16th International Conference on Manufacturing Research, incorporating the 33rd National Conference on Manufacturing Research, September 11 – 13, 2018, Skövde, Sweden / [ed] Peter Thorvald, Keith Case, Amsterdam, Berlin, Washington,DC: IOS Press, 2018, Vol. 8, p. 381-386Conference paper (Refereed)
    Abstract [en]

    The manufacturing industry has a duty to minimize their environmental impact and more and more legislations include environmental impact evaluations from a life cycle perspective to avoid burden shift. Current manufacturing industry increase their use of computer-based simulations for optimizing production processes. In recent years, a number of studies have been published, combining simulations with life cycle assessments (LCA), to evaluate and minimize the environmental impact of production activities, as part of improving the production processes. Still, current knowledge concerning simulations for LCA is rather scattered. Therefore, this paper reviews relevant literature covering simulation based LCA for production development. The results of the review and cross comparison of papers are structured following the 6 categories in line with the ISO standard definition of LCA (goal formulation, scope definition, environmental impact assessment, data quality, level of modelling details, and model validation) and report the strengths and constraints of the reviewed studies. 

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