User guide

Appendix l C-2
All about Cutter Bushings
• If you are cutting a square or rectangular profile, whether rigid or flexible,
a round bushing bore will not offer proper support and will often lead to
an "S" shaped cut. A flat bottomed bushing will offer excellent support and
enhance the shearing action of the blade.
• In the case of flexible extrudates, allow 0.010-0.050 inch clearance
depending on durometer and surface; the softer durometers and tacky sur-
faces require the most clearance. In the case of softer durometer materials,
bushing lubrication may be required to minimize drag and material build-
up between the cutter bushing faces.
Cutter bushing bore surface quality
The internal surface of the cutter bushing must be smooth and glass-like when cut-
ting flexible extrudates, otherwise excessive drag causes jamming and can lead to
variations in cut-to-length accuracy.
• When cutting flexible materials, have the internal surface machined to
resemble glass. In many cases, medical processors will actually have the
ID of their bushings either honed or burnished for best results.
• When cutting clear extrudates, it is also very important to have a smooth
internal surface to minimize scratches. In some cases it may be necessary
to make a Teflon or Delrin insert to further minimize drag and/or scratch-
ing.
• Bushing lubrication can also help minimize bushing drag.
• Be sure to have a lead-in angle machined into the entrance of the upstream
cutter bushing. The transition from the bore to the lead-in angle should not
be abrupt as it to can cause variable drag.
(continued)