Basic analysis and optimization of the flow behavior of thermoplastics by adjusting the surface of electrical discharge machined injection molds (EDSIMP)

 

Laser radiation has been used for many years in a wide variety of processes in industrial manufacturing technology. Traditionally, depending on the process, either a continuous wave - cw or a pulsed wave - pw, laser is used. On the other hand, the dual beam process developed at WZL and Fraunhofer IPT for flux-free laser brazing of aluminum is used, in which a cw and a pw laser are used simultaneously. Due to the naturally present oxide layer on aluminum, the joining of aluminum and aluminum-steel mixed joints poses a particular challenge. The pulsed laser used in addition to the actual continuous process laser enables flux-free removal of the oxide layer and the formation of a joint in the dual beam process.

Previous research projects have already provided important insights into the pulsed laser effect and a process model has been developed. In some areas, however, the physical understanding of the mechanisms involved is still incomplete.

On the one hand, the question arises as to what effect the plasma produced by pulsed laser-induced material evaporation has on the absorption of the continuous laser beam and thus on the workpiece temperature during the process. On the other hand, it has not yet been completely clarified whether only the removal of the oxide layer or also the topography change of the substrate surface due to pulsed laser ablation and the associated change in wetting with the solder is decisive for the process. A third question arises with regard to the pressure effect of the plasma on the melt and how this can be specifically used to influence the geometry of the weld or solder seam. This aspect is also of interest with regard to the possible application of the two-beam process as an additive manufacturing process.