Page 360 - Injection Molding Advanced Troubleshooting Guide

356 37 Pin Push

„ „37.2„ Pin Push Troubleshooting Chart

Table 37.1 shows the pin push troubleshooting chart.

Table 37.1 Pin Push Troubleshooting Chart
Molding Process Mold Machine Material
high or low second- sticking machine performance release agent
stage pressure
low or high mold lack of ejection ejector plate moisture content
temperature
high melt temperature lack of draft velocity to pressure fillers
transition
fast ejector speed cavity balance
cooling time

„ „37.3„ Pin Push Troubleshooting

Pin push usually is a defect where the ejection force on a part distorts the wall of
the part. Many factors can impact the tendency of the wall stock to be distorted
resulting in pin push.

37.3.1„ Pin Push Troubleshooting Mold Process Issues

Molding concerns for pin push include the following:
ƒ High or low second-stage pressure
ƒ Low or high mold temperature
ƒ High melt temperature
ƒ Fast ejector speed
ƒ Cooling time

37.3.1.1„ Molding Process: High or Low Second-Stage Pressure

Second-stage pressure has a large impact on how a part sticks or shrinks onto a
mold. Depending on the detail on the ejector side of the mold both over-packing
and under-packing of the plastic can lead to pin push.
Over-packing of the plastic can reduce the amount of shrink on the molded part,
which can in turn lead to ribs and other details that are packed so tight that they