User guide

C-5 l Appendix
All About Cutter Bushings
Adjusting the cutter bushing gap
If the bushing gap is too big, material is dragged down between the bushings creat-
ing a burr, especially with flexibles. This may lead to jamming within the bushings
where the upstream side of the cut extrudate actually hits against the downstream
bushing surface. This is especially apparent with flexibles with non-concentric
walls where a slight bow is present.
• Locate the downstream bushing such that it touches the blade without
deflecting it. Lock it in place and rotate the blade to check proper gap.
• Locate the upstream cutter bushing with 0.001-0.002 inch of the blade and
lock it in place. Rotate the blade through the set bushings to insure proper
gap. NOTE: Because blades are rarely perfectly flat, it is possible that a
swishing sound will be heard.
• If hairs are present on only the upstream cut end of a tube or profile, it
may be necessary to allow a 0.002-0.005 inch gap on the downstream
bushing to allow the blade to slightly move with the extrudate during the
cutting cycle and not cause excessive frictional heat which actually melts
the extrudate. NOTE: Blade/bushing lubrication can also help to solve this
problem.
(continued)