Delamination (peeling)
The surface layer peels off the part and separates in flakes.
Symptoms
- A layer comes off when tape is pulled from the surface
- Layered appearance on the fracture surface
- Flaking around the gate
Tip: Tape test: stick tape onto the surface and pull it off; if a layer comes off, contamination or incompatibility is very likely.
Order of solutions
- Check the raw material and the regrind; remove the contamination by a different polymer
- Clean the barrel and the hot runner
- Increase the melt temperature, reduce the speed at the gate
- Enlarge the gate
- Dry the material if necessary
Likely causes
Process setting
- Excessive shear (high speed, small gate)
- Low melt temperature
Raw material
- Contamination with a different polymer (e.g. PE/PA in PP)
- Incompatible blend
- Moisture
Mold
- Small gate or sharp gate transition
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Other defects
Short shot (incomplete fill)
The cavity does not fill completely; the farthest or thinnest area of the part stays incomplete.
Flash
Plastic escapes through the parting line or around the ejector pins.
Sink mark
A dent on the surface opposite a thick section; the surface is drawn inwards.
Void (internal vacuum void)
Internal cavity in a thick section of the part; the outer surface may look perfect.