Page 231 - Injection Molding Advanced Troubleshooting Guide
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222 23 Contamination
One key to avoiding material contamination is to clearly label all materials in every
hopper or container. Before new material is loaded into a hopper or machine the
label should be cross checked to verify that the correct material is being added. If
a silo is contaminated the result can be thousands of pounds of scrapped material
plus the lost time.
Complete cleanout of everything that a material touches is a must. All tankers, rail
cars, feed lines, silos, hoppers, storage bins, and grinders must be cleaned thor-
oughly before introducing a new material. A few pellets left over during a change-
over can yield scrap for hours. See Section 23.3.1.1 for more details on changeovers.
Mismatched materials can show as many different defects including contamina-
tion, delamination, black specks, color streaking, and splay.
