Process Window for Forming of Micro Preforms at Different Temperatures

Parts, which dimensions do not exceed the micro range are gaining more importance in today´s goods due to miniaturization and function compaction of products. Thus, fabrication methods for these special, very small parts attract notice because whole processes or at least process parameters cannot be transferred into micro range. Nevertheless, this does not necessarily mean, that size-effects are always detrimental as there are some processes which can only be carried out in micro range such as the laser-based micro upsetting process. The basic characteristics of this process are presented in this paper such as its self-aligning capability. Due to the fact that the maximum achievable upset ratio in single stage upsetting decreases with decreasing sample size, the material accumulation represents a very good semi-finished product (preform) being formed in a succeeding upsetting process. A temperature- and time controlled forming unit has been developed which is directly adapted to the laser system which is required to generate the preform. Thus, either a pre-defined temperature of the preform or the down time gives the initial signal to start the forming process. In this paper, a mathematical model is very briefly presented to determine the process window for forming preforms at certain well defined temperatures regarding size-effects.