As a molder, we are responsible for the processing of your part. Making sure it meets its component criteria. As the designer, you are responsible for the part meeting expectations in its design application. Many mechanical engineers are more heavily educated and experienced in metals. If your application includes heat exposure, it is important to understand how plastic reacts to heat differently than metal.
For plastic part designs or even more importantly metal to plastic conversions, you need to account for how will plastics react to heat in your design. Metals tend to maintain their mechanical characteristics well through the range of room temperature up to their melting point. Plastics on the other hand, due to their molecular make-up, react differently to heat. As temperature rises, plastics first experience their glass transition (Tg) temperature and then ultimately reach the melt temperature (Tm). Between those two temperatures, the plastic is susceptible to mechanical forces, making them behave differently from metals. It is a characteristic that you need to consider in your product design. Different plastics have different Tg specifications. The Tg can be altered using fillers and additives (also known as a composite). Matching up the right plastic or composite with your design application is a critical step and one where your processor can be of assistance.
Include that ability in your selection of an injection molder. Along with assessing their ability to mold plastic and composites, actually understanding the dynamics of the plastic for your end application can be invaluable. We are fortunate at PlastiCert to be located near the only university in the United States (Winona State University, Winona, MN) that offers a major in Composites Engineering. We are also happy about having staff that are products of the program. We act as a resource for our customers when they are trying to decide from the 70,000 odd plastics out there. We can provide guidance on which direction to go for your application. What are you expecting your plastics processor to do?
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