Experimental Investigation of the Robustness of Bulk Metallic Glass-Based Tooling for Microinjection Molding

Abstract

The primary objective of this research was to experimentally investigate the robustness of a commercially available zirconium-based bulk metallic glass material (Zr-based BMG) for microinjection molding (μIM) tooling. The focused ion beam (FIB) direct milling process was utilized to fabricate microfeatures onto two BMG-based mold inserts. Uncoated and Ti-coated inserts were inspected through molding cycles utilizing SEM. Additionally, TPU molded samples were characterized to quantify the replication quality of the inserts through molding cycles. This is to understand the polymer melt effect of the tooling during molding conditions. The uncoated BMG insert was utilized for more than 1000 molding cycles regardless of the potential crystallization. No signs of any crack initiation were observed in any part of the BMG insert. Through molding process, the replication quality degraded due to the polymer adhesion to the microcavity base. In the case of the coated BMG insert, the coating could not withstand the high ejection force during demolding stage. The adhesion between the coating and the BMG surface was insufficient to survive molding conditions. This resulted in disintegrated coating that was bonded into molded samples.