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Appendix 5 Troubleshooting constant
banding caused by gear teeth
•
A defective or dirty tooth on one of main gears causes constant banding.
•
You will probably not find them it in the Constant banding table.
•
Constant banding - Some separations
A defective tooth on the PIP gear usually causes banding on the some separations. This is because
alternate separations are produced on the same side of the PIP drum (MK on one side of the PIP and YC
on the other side).
•
Constant banding - Each separation
A defective tooth on the ITM gears or impression drum usually causes banding that appears on each
separation.
Locating a defective or dirty tooth on the ITM drum gear or
impression drum gear
Banding due to a defective or dirty tooth on ITM drum appears on each separation.
1. Mark the banding on your print sample.
2. Press the Inching button and insert the printed page into the grippers.
3. Using the hand wheel, manually rotate the press, and keep your eye on your band.
4. Stop rotating one or two centimeters before your band reaches the ITM drum.
5. Mark the gear tooth (e.g. with a small sticker or with tip-ex) in line with your band. See Figure 17.
6. The defective or dirty tooth will be in a range of 3 to 5 teeth on either side of your mark.
7. Clean and inspect this area.
Figure 17 Marking the defective or dirty tooth on the ITM drum
Locate the defective or dirty tooth on the PIP drum gear
Banding appears on some separations: alternate separations (1
The defective or dirty tooth may be on either half of the PIP drum. Null cycles can occur at any point in
between separations. This makes it difficult to determine which PIP half has the defective tooth. Therefore
we will troubleshoot both halves of the PIP drum at the same time.
22 Appendix 5 Troubleshooting constant banding caused by gear teeth
The banding
Location of problematic tooth
st
rd
nd
th
& 3
or 2
& 4
).
EN
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Troubleshooting
