Estimate injection molding time for plastic parts

[chark]

How do you estimate injection molding time for plastic parts? What is the critical data needed?

 

[THannibal]

Cooling time is the key for estimating the molding cycle time.

Minimum cooling time is a function of:

1) Wall thickness
2) Difference between polymer and mold temperature
3) Difference between mold release temperature of the article and mold temperature.

Minimum cooling time could be estimated from the following
equation:

S=(-t^2)/(2(pi)alpha)*log e (pi(Tx-Tm)/4(Tc-Tm))

S= minimum cooling time (sec)
t= thickness of molding (in. or cm)
alpha=thermal diffusivity of material (in^2/sec or cm^2/sec)
Tx= ejection temp of molding (often heat distortion temp)
Tm= mold temp.
Tc= cylinder temp.

This equation is from the book "Injection Molding Handbook"

Hope this helps.
Good luck.

Ted Hannibal
IBIS Associates, Inc.