The effect of rapid tooling on final product properties

The development of a plastic part frequently involves several prototype iterations. Production of these prototypes with conventional metal tooling often results in high costs and long lead-times. A group of materials and processes known as rapid tooling can produce a limited number of prototypes faster and more economically than conventional tooling. However, differences in the thermal properties of conventional and rapid tools resulted in mechanical property differences in the final plastic parts.; Using a rapid mold selection procedure, important properties of rapid molds were identified and candidate materials were tested. From this process, several candidate materials were fabricated into injection molds. The method and techniques necessary to fabricate each type of tool were also discussed.; With a fixed mold design and optimized injection molding conditions, the tensile and flexural properties of atactic and syndiotactic polystyrene molded in steel, aluminum, and five types of rapid tools were compared.; In flexural testing, parts from both isomers produced in the rapid molds exhibited higher flexural strength, higher flexural modulus, and lower ultimate flexural elongation than parts produced in the steel and aluminum molds. The frozen skin thickness and magnitude of the residual skin stress were quantified and argued to be the predominant factors in the flexural properties of atactic and syndiotactic polystyrene. The frozen skin thickness was correlated explicitly with the flexural properties of atactic and syndiotactic polystyrene.; In addition, the tensile and flexural properties of polypropylene, acrylonitrile-butadiene-styrene (ABS), and polycarbonate parts molded in steel and backfilled stereolithography (SL) molds were compared. The characteristics of each polymer determined the magnitude of the observed property differences.; In order to understand how different mold materials and construction techniques affected the heat transfer characteristics of the part and mold, a one-dimensional multi-cycle heat transfer model for layered composite molds was developed. The model provided an accurate prediction of experimental data for the first 100 seconds of heat transfer.; The C-Mold injection molding simulation software package was intended to provide insight into the injection molding experiments as well as support the mechanical property results. However, several caveats made it inappropriate for use with rapid tools. (Abstract shortened by UMI.)...