JING YANG
M.S. in Mechanical Engineering, December, 2006
Advanced Materials and Technologies Laboratory
University of Connecticut

 

ANALYSIS OF A PROCESS FOR RAPID REPLICATION OF ELECTROFORMING MICROMOLDS.

Electroforming is an important step in the fabrication of microparts using the LIGA (an acronym for the German words for lithography, electroplating and molding) process. This thesis considers a novel process for rapid replication of thermoplastic electroforming LIGA micromolds incorporating metallic microscreens. During the process, the walls of the microfeatures on the mold stamp are subject to the pressure forces imparted by the flowing thermoplastic melt. The pressure forces on the two sides of the mold feature walls are often unbalanced because of the non-uniform distribution of fluid flow or the different sizes of the cavities adjacent to the mold walls. The unbalanced pressure distribution results in bending stresses on the mold walls, which might lead to a catastrophic breakage of the mold features. To improve the mold life, the effects of mold temperature, inlet polymer melt temperature, flow rate, and cavity width on the mold stress are investigated in this thesis. A computational simulation model is implemented for the process, which forms the basis for a systematic parametric exploration. The parametric studies are used to obtain operating range of the injection molding parameters as well as design guidelines on the mold feature layout so as to eliminate catastrophic mold failures.