During turning, processes are faced with tough tolerances that can be difficult to maintain due to vibrations and bending. The company Volvo Cars would therefore like to examine the work station OP30, which is a turning process for crankshafts, to better understand why this is. The company has the ambition to implement virtual analyses with the finite element method (FEM) in its production lines. This is sought after to prevent physical examinations which can cause delays due to time-consuming physical tests. In order to investigate the causes for the tolerance not being met, the crankshafts deflection will be examined using FE-analyses that will consider the clamping conditions of the crankshaft, the centrifugal forces and the cutting forces. The natural frequencies of the crankshafts are also examined to confirm that the turning process is not carried out near any critical rotational velocities.
In order to verify the FE-analyses performed on the crankshafts, an analytical calculation based on beam theory of a simplified geometry is made using MATLAB. This is then compared with FE-analyses of the same simplified geometry, which shows that solid models used in FE-analyses gives reliable results compared with the beam theory. In order to confirm the deflection that is obtained from the FE-analyses, a measuring method using laser triangulation is developed. This is tested on a lathe at the University of Skövde.
The results of this work show that the FEM is a good approach for examining the deflection of a complex geometry. It also shows that the deflection that occurs due to centrifugal forces can be considered small compared to the tolerances that need to be met and the deflection that occurs due to axial displacement of the crankshaft. Therefore the conclusion is drawn that the deflection due to centrifugal forces is not the main source for the tolerances not being met. The work shows that the most important factors to consider are the cutting forces and the axial displacement of the crankshaft. It also shows that there is no risk of resonance occurring within the work parameters of OP30. The work also shows that the measuring method using laser triangulation can be used on a rotating crankshaft, although the equipment used cannot measure the deflection itself.