Screw and Barrel Wear
Screw and barrel wear is critical in all plasticating applications whether it is extrusion, injection molding, and blow molding, plus twin screw extrusion.
Excessive screw and barrel wear can cause instable throughput or recovery on reciprocating screws, increased melt temperature and reduced plasticating rates.
Some of the causes of excessive wear are:
- Screw straightness
- Barrel straightness
- Barrel alignment to the gearbox
- Screw/barrel concentricity
- Screw speed
- Screw flight to Barrel liner compatibility
- Polymer being processed
- Fillers in the polymer
- High head pressure
The following chart shows the typical rebuilding requirement for various applications. Critical would be for a close-tolerance product and non-critical may be for a process such as making plastic lumber.