Adjusting process parameters in zamak-8 prototype tooling to obtain functional prototypes in PP

Abstract

Prototype tooling is an option to obtain functional prototypes, or even final parts, in low-scale injection molding. In order to reduce the manufacturing time and cost of this type of tooling, alternative materials, such as zinc alloys, can be employed. However, the mold material and injection parameters can influence molding crystallinity and mechanical properties. The zinc alloy known as zamak-8 has not been explored much for this application. The objective of this work is to study the influence of this mold material on the properties of polypropylene (PP) when varying the mold (T m) and injection (T i) temperatures. Then, based on that, to develop some regression models to help obtain PP moldings in the zamak-8 mold with similar characteristics to those injected in a steel mold, which was used as a reference, the characterization techniques used were tensile and impact tests, and differential scanning calorimetry as well, to measure crystallinity. The results showed that zamak-8 prototype tooling only has a significant influence on the impact strength of the injected PP. The regression models showed that to obtain injected prototypes with mechanical and crystalline properties close to a production part in this specific study, T m should be set at around 40 °C and T i at 225 °C. In general, this indicates that zamak-8 can be used to obtain functional prototypes in PP with similar properties to the production parts.