The thermal advantages of copper-alloy cores are conclusive and accepted by the industry. However, the industry is concerned about the life of copper-alloy mold components.
The research team at Western Michigan University has experiments underway to compare the life of copper alloys protected with a variety of hard coatings to the life of P-20 steel. Aggressive erosion and stripping wear conditions have been designed into an eight-cavity mold that is producing glass-filled nylon parts. Copper-alloy cores have been coated with the following:
- Electroless nickel
- Hard chrome
- Titanium nitride
- Thin dense chrome
- Thin dense chrome with diamond particulates
Quantifiable results will have to wait for the experiments to be completed, but the initial trends show that, for at least one of the coating systems, the copper alloys will have lives equal to or better than P-20.
In the process of adjusting the mold to intensify the wear rate, the research team reduced the wall thickness of the part being molded. This change allowed the researchers to learn several things to consider when designing a mold to withstand wear.
Thin wall design may cause a stable skin of solidified plastic to be washed away by the hot polymer melt and significantly increase erosive wear.
While wear was expected on the core opposite the gate, unexpected wear occurred where the melt washed back against the steel cavity wall a short distance from the gate.
If you would like to receive the report on the long-term wear study when it is completed, contact CDA at 212-251-7200.