It is important that when designing plastic parts you consider the various aspects of cooling, and how they affect the finished product.
Topics in this section
Cooling time Cooling time is the time after the end of packing until ejection. Usually, the material at the center section of a part wall reaches its freeze temperature (Vicat softening point) and becomes solid during cooling time. Cooling time usually represents 80 percent of the total cycle time.
Ejection temperature
The ejection temperature is the temperature below which the plastic is solid.
Heat transfer
The mold can be thought of as a heat exchanger because heat passes into the mold and transfers out of it.
Heat transfer due to coolant flow
The effect of heat transfer increases as the flow of coolant changes from laminar flow to turbulent flow.
Heat transfer effectiveness
A heat transfer effectiveness (HTE) value can be assigned to mold surfaces to indicate the effectiveness of heat transfer through specific mold surfaces.
Cooling system equations
Theoretically, cooling time is proportional to the square of the heaviest part wall thickness and the largest runner diameter raised to the power of 1.6, and inversely proportional to the thermal diffusivity of the polymer melt.
Interface conductance
Interface conductance is a measure of the rate of heat transfer across the surfaces represented by inserts and parting planes.
Mold materials
To run a Cool analysis, all mold model surfaces must be defined with a mold material. This allows an accurate estimate of cooling rates in the design, using the properties associated with that mold material.