Perfecta 115 TS - Convex Cutting; Friction between the Knife and the Clamp; Knife Chipping

Service Manual 10 Cutting Quality Enhancement Tips
10.1 Trouble occurring/cutting problems and their remedies
1/09 PERFECTA 115 / 132 / 168 / 225 – TS 65
PERFECTA Schneidemaschinenwerk GmbH  D-02625 Bautzen  Schäfferstr. 44  Tel.: +49-3591-556-131 to -133  Fax: +49 3591-556-139
10.1.5 Convex cutting
The paper sheets are shorter at their ends than in the middle.
Cause Remedy
In its middle, the pile is pressed down
stronger than at its ends.
Check the clamp edges and place a felt or
foam pad underneath, if necessary, to
distribute the pressure more uniformly.
Wet material is used for processing
reasons (containing tension).
After you obtain a convex cut, make a
second cut.
Table 9: Causes of and remedies to convex cutting.
10.1.6 Friction between the knife and the clamp
The knife back is rubbing on the clamp. Both the knife and the clamp get marks.
Cause Remedy
The knife is dull and is deflected because
of the increasing pressure.
Replace the knife with a resharpened
one more often.
The knife is too thick or curved. Check the knife thickness and whether
the knife is straight. If necessary, grind it
thinner or straighten it.
Wrong cutting edge angle. Reduce the cutting edge angle.
Too much clamp guidance play. Readjust the play correctly.
There is a combination of the above
causes including an excessive pile
height.
Check for the above causes and reduce
the pile height.
Table 10: Causes of and remedies to friction between the knife and the clamp.
10.1.7 Knife chipping
Cause Remedy
Wrong cutting edge angle. Increase the cutting edge angle or grind
a bevel (double angle).
Knives which are highly overheated during
grinding get thermal cracks causing chip-
ping.
Resharpen the knife with sufficient coolant
supply. The damaged zones must be
completely removed.
The knife penetrates too much into the
cutting stick.
Replace the cutting stick with a new one
and adjust the correct cutting depth.
The cutting stick quality is not suitable
for the knife.
Choose a cutting stick which is suitable
for the knife.
Contaminated or coarse cardboard. Increase the cutting edge angle or grind
a bevel (double angle).
Do not use a carbide knife.
Table 11: Causes of and remedies to knife chipping.