Page 260 - Injection Molding Advanced Troubleshooting Guide
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26.3 Dimensions Troubleshooting 251
Figure 26.7 shows 10 consecutive shots with significant second-stage pressure and
time variation. The part being molded in this machine was showing dimensional
variation and needed frequent adjustments. A portable process monitoring system
was put on the machine and it was quickly apparent that there was a major
machine problem. In this particular case a valve on the molding machine needed to
be rebuilt; after rebuilding the valve the problem was resolved.
See Chapter 8 on machine performance for more information.
Figure 26.7 RJG eDART showing 10 consecutive shots with second-stage pressure variation
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26.3.4 Dimensions Troubleshooting Material Issues
As with any defect it is important to verify that the correct material is being used.
In general, unfilled semi-crystalline materials will shrink more than filled and
amorphous materials. If the part is consistently having a dimensional problem
there are some things that may be worth evaluating for improvement. Items to
consider if having dimensional issues are:
Filled material
Nucleating agents
Material type
