Page 220 - Injection Molding Advanced Troubleshooting Guide
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23.3 Contamination Troubleshooting 211
vacuumed out to help with clean out. Watch out for areas such as the sample
tube because this is a spot that is often forgotten.
Feed lines. Whether feeding the machine from the drying hopper, gaylord, or
bag, it is critical to ensure that all of the material has been cleaned out. This is
usually as simple as removing the feed line and allowing the vacuum loader to
suck all of the material out of the feed lines. There have been cases were the
material handler does a nice job of cleaning everything out but forgot the feed
lines and when the new material was introduced all of the previous material was
pulled in with it, contaminating the material.
Machine hopper. The machine hopper will have a variety of locations where ma-
terial can collect. Make sure to remove the magnet and clean out around the
magnet drawer (see Figure 23.2). The hopper should be completely cleaned of all
residue from the previous material. Also be sure to watch for any mismatch
ledges between components such as the feed throat and hopper.
Loaders. Loaders can also be a location that will trap material pellets. All loaders
must be cleaned as part of the material changeover process.
Additive feeder bins. Additive feeder bins must be cleaned when swapping
colors. The feed screw on a volumetric feeder must also be removed and cleaned
to avoid contamination.
Figure 23.2 Pellets stuck in magnet drawer
