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15.3 Black Specks Troubleshooting 139
15.3.4.2 Material: Wrong Material
If the wrong material is loaded into a molding machine many potential problems
can occur including black specks. If the material is overheated it can degrade,
which could lead to black specks. It is important to make sure that the correct
material is being used in all cases. Normally there will be a multitude of issues
that show up if the wrong material has been loaded, but it is always a good thing to
verify when troubleshooting.
15.3.4.3 Material: Regrind Fines
When plastic runners and parts are run through a grinder there can be inconsis-
tent grind and a level of fines or dust (see Figure 15.7). These regrind fines will
have a tendency to melt early in the barrel and as a result will tend to degrade
more easily.
Dusty regrind is often times a sign of dull grinder blades that are beating the ma-
terial more than cutting it. Maintenance of grinders should include blade sharpen-
ing and setting of blade to mesh gaps per recommended specifications.
Figure 15.7 Regrind fines
