Page 376 - Injection Molding Advanced Troubleshooting Guide
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39.3 Scuffs and Scratches Troubleshooting 373
Incorrect loading of pack
Dropping parts on the floor
Stacking parts on top of each other
Poorly designed packaging that does not protect the parts
Bulk packing parts that should be cell packed or layer packed
Improper trimming by the operator
Thorough inspection of the part handling after it has left the equipment is an im-
portant step to diagnosing handling problems. Often times one of the above items
will result in parts being damaged at the operator station.
Case Study: Scratching Parts
This example was a case where the first step in troubleshooting was under-
standing the true defect. This particular polypropylene part was experiencing
high scrap numbers for splay. Using the Think step of the STOP process high-
lighted that splay is not usually a problem on unfilled polypropylenes. Using
the Observation step showed that what was being scrapped as splay actually
had scratches that were occurring as operators bumped the parts against a
sharp corner on the work table. The corner was fixed and the “splay” prob-
lem was gone.
It is important to let just one piece flow through the operator work station on parts
that are at risk for handling damage. When multiple parts are at the work station
there is a much higher likelihood that parts will be stacked or banged against each
other resulting in damage.
39.3.2 Scuffs and Scratches Troubleshooting Mold Issues
There are certain features in mold design that can lead to concerns with handling
damage including:
Texture
Lack of ejection
Parting line damage
39.3.2.1 Mold: Texture
When a mold is textured it is important to make sure that the texture is not too
deep for the draft of the part because otherwise scuffing will occur. When inade-
quate draft is used with a given texture the peaks of the texture on the part will
drag as the part is ejected, which will leave behind texture damage in the form of
scuffing.
