How can pimples or specks be avoided in extrudates?

This fault points to various possible causes:

1. Rolls contaminated (regular return of surface defects according to roll circumference)

Remedy:
Clean rolls

2. Impurities in melt stream

Remedy:

• Check melt stream for impurities
• Increase contact pressure of calender rolls
• Increase roll temperature
• Clean extruder, remove screw

 
3. Impurities from air (dust, fines)

Remedy:
Reduce distance between die/calender stack

back