In this month’s webinar, we’ll examine the topic of plastic cooling rate. The rate that the parts cool in the cavity influences many of the finished part properties. Cooling rate is controlled primarily by the mold coolant temperature.

The design and layout of the cooling circuits in the mold play an important part in final part properties. More cooling is required in areas of the cavity where there is more plastic. Often there are several different cooling circuits in the mold to accommodate the need for more or less cooling depending on the part design.

In general faster cooling locks more molecular orientation into place near the surface of the part. It also forces more shrinkage to occur away from the part walls. Cooling time is the longest part of the molding cycle. The goal is always to cool the part as quickly as possible to minimize the cycle time while maintaining part properties .

For crystalline plastics, like polypropylene and polyethylene, the rate at which they cool affect the amount of crystalline formation, which in turn affects the amount of shrinkage.

Topics covered include:

• How cooling rate affects part properties
• How cooling rate affects crystal formation in crystalline plastics
• Best operating practices for coolant in/out temperatures
• How to minimize cooling times to achieve quicker cycle times