Problems of accuracy control in cold forming

Modern manufacturing technologies demand components produced to very narrow tolerances: the number of non-satisfying parts is nowadays limited to some tens per million, the final goal being “zero-defect production”. In order to fulfil these preconditions, the forming processes must be well understood and kept under permanent control. The geometrical accuracy of cold-formed components depends on many parameters, among which the most important are the incoming material, the machine, the tools, and the process itself. This paper first discusses some efforts in analysing the impacts of different process parameters where a combination of experiments and numerical evaluations was used. The research was oriented towards ranking of the parameters, according to their influence and studying their interrelated effects on the processes. In the final sections, an interesting phenomenon concerning the accuracy control were presented: it is possible to find such a combination of parameters where the process is stable, and not so sensitive to the fluctuations of parameters. The definition of such “stable technological windows” will be very valuable for practice, especially for technology planning.