Prozesscharakteristiken des thermischen Stoffanhäufens in der Mikrofertigung

Abstract

Conventional single stage cold upsetting processes are limited to upset ratios 2 in micro range due to size effects. To still benefit from the advantages of upsetting, an alternative process chain called "laser rod end melting" is presented in this work. Prior to cold forming, the wrought material is locally melted by a laser beam whilst the surface tension causes the melt to form spherically, called "preform" . Experimental investigations show that the master forming stage allows geometrical tolerance IT9 in diameter of preform. An analytical, non-adiabatic model is set up describing very well the master forming stage in terms of pulse energy, deflection velocity and preform diameter. The dendritic grain structure of preforms does not show any deficits when forming is carried out in cone-shaped dies and it is possible to replicate surface structures as small as 0,001 mm. Hence, this work shows that the laser rod end melting process is well suitable to significantly shorten multi-stage cold forming operations.