Page 452 - Injection Molding Advanced Troubleshooting Guide

452 45 Voids

„ „45.2„ Voids Troubleshooting Chart

Table 45.1 shows the voids troubleshooting chart.

Table 45.1 Voids Troubleshooting Chart
Molding Process Mold Machine Material
low second-stage pressure cooling machine performance
short second-stage time thick sections
low or high mold temperature gate location
high melt temperature

„ „45.3„ Voids Troubleshooting

Voids are often overlooked because they are not visible on an opaque part. Trans-
parent parts will visually show voids; they will most often appear in thicker wall
stock areas. Voids may lead to a decrease in physical properties on the molded part
so it may be necessary to cut a cross section of the parts to ensure the process is
not producing voids.
Design can play a major impact on voids. If nominal wall stock is not maintained or
if a part is gated thin to thick the likelihood of a void forming will rise. Many of the
same concerns in part design that will be sink makers can also lead to voids. Try-
ing to process around a poor part design will lead to narrowed process windows
that will raise the cost of production on a part.

45.3.1„ Voids Troubleshooting Molding Process Issues

Molding process issues impacting voids are:
ƒ Low second-stage pressure
ƒ Short second-stage time
ƒ Low or high mold temperature
ƒ High melt temperature