Rockwell Automation 1771-QDC, D17716.5.93(Passport) PLASTIC MOLDING MODULE - Manual (Page 18)

Overview of Inject, Clamp, and Eject Mode
Chapter 1
1-6
Example Benefit of Profiling the Pack Phase
Molten plastic may cool unevenly in the mold causing variations in density
with the end result of warpage and distortion as shown in Figure 1.6.
Figure 1.6
Uneven Cooling in Pack Phase
Gate
Time
1 2 3 4 5
Density in Mold Cavity
Pack Profile
Lower density
(last zone filled)
Higher density
(gate zone,
greater pressure)
Pressure
You can remedy this by decreasing the pack pressure with time so plastic
can back out of the mold as shown in Figure 1.7. This is to alleviate
gradations in density as the plastic cools from the low-density end of the
mold (last zone filled) to the high-density end of the mold cavity (gate
zone where pressure is greater).
Figure 1.7
Even Cooling in Pack Phase
Gate
Time
1 2 3 4 5
Density in Mold Cavity
Pack Profile
Pressure
Constant Pressure over entire Mold Cavity
After completing the last segment of the pack phase, the QDC module
automatically starts the hold phase.