Page 392 - Injection Molding Advanced Troubleshooting Guide
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390 40 Short Shot
Figure 40.8 Sliding ring check valve
Figure 40.9 Ball-style check valve
With a leaking non-return valve the cushion value on the machine will either show
a large amount of shot to shot variation or will consistently reach zero. Another
clue that the non-return valve is leaking is to watch for the screw to rotate during
injection because this is a sign that backflow is rotating the screw. Sometimes the
cushion may not be reaching zero because the transfer position was large enough
not to bottom the screw out. Adding second stage time will highlight if the screw
stops moving or continues to travel until it bottoms out.
40.3.3.2 Machine: Wrong Nozzle
There are many choices for nozzles and nozzle tips that can be used on a molding
machine. Each tip choice can impact the pressure on the machine. Nozzle concerns
include:
