Determining of cumulative dimension deviations in multi – part sheet metal constructions by means of measurements and analyses and development of an algorithm

Today, by producing an industrial product design, manufacturing and measuring systems and quality management processes are interlaced and bonded with powerful links. These links have become in the time to a functional state and the provided improvements have formed the basis of Industrial 4.0 Revolution. Industrial establishments are trying to build the aforesaid functional links and to reinforce their databases. So, they have the possibility of the revulsion of being behind the times. Because the automotive industry is one of the main sectors where this point of view can be seen dominantly, the practical application field of this thesis has been chosen from here. So, in the selected chasis group, tolerances, tolerance stack-up analyses and distortions after welding are being handled. Distortions before welding and after welding are being evaluated with design criterions and process parameters and an approachment method is being created. So the estimation of the stack-up of dimensional and form deviations is being aimed. The created approachment method is in a structure that can be converted to intelligent systems by arriving of new parametric values coming from analyses and applications. In the establishment, with feedbacks got from the serial production, the sustainability of the method and its adaptation for new groups and parts can be provided. The method can be linked in the context of Industry 4.0 to its other factors and applications. The providing of nominal dimensions during the application of manufacturing processes can not be possible because of technological and financial restrictions. Hence, tolerancing is very important for a successful assembly. Determining tolerances for complex parts and assembly groups in the design stage is a hard job. Because assigning the foreseen tolerances and the ones which can be realized during manufacturing is based not only on the knowledge but also on the experience. Small dimension and form tolerances are accumulated cumulatively and cause that the last tolerances can not be adapted. The main aim of the thesis work is to predict the last stage during geometrical and welding process designs and to help to the designers. Although today some approximation models for specific surfaces appear, there is not a mathematical model yet which represents the tolerance during assembly directly. Because sheet metal parts are considered for applications in the thesis work, the pimary two factors affecting on deviations are the springback after forming and distortions after resistance spot welding. The form deviations after forming can be obtained with the method scanning and welding distortions obtained with analysis method can be added to this data. During that stage, the mathematical relation formula between distortions and welding parameters can be used and the parameter limits will have been found with specific tests. The second arm of the thesis work is, without showing any correction effort, mating the singular parts with each other by accepting the deviations after manufacturing as they are and by meeting the optimum cumulative tolerances. So, a software has been created to optimize the cumulative tolerances by using the singular deviation datas which can be obtained from the measurements of parts. This software mates the singular parts according to Tolerance Analysis methods and so the groups for assembly before welding become ready. At the end of the thesis work, the generated mechanization of the system has been designed and ist protype has been manufactured and made ready for functioning. The patent application for this system has been made. In conclusion, the made thesis work will provide designing tolerances, geometrical dimension and form and welding process parameters according to the standards in an integrated manner. It will make possible the transition from singular tolerances to optimum cumulative tolerances. So, these proposed systems can be transformed to intelligent systems, after continuing works after the thesis and it is aimed to help to the way reaching of Industry 4.0 Revolution. Keywords: Cumulative tolerance, Statistical Tolerance Stack-up Analysis methods, resistance spot welding and parameters, mating