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moire patterns during printing
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old-gmpx


Joined: 06/12/2006 00:45:36
Messages: -25
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we are having problems with moire patterns appearing during printing. We have tried using different sources for preepress and there are still inconsistencies..

I am a designer working with a printers in Southeast Asia. We have been getting problems with moire patterns appearing. Thinking it is screen angle problem, we have tried changing our prepress provider, still 'sometimes' the moire appears. We are using a reconditioned Heidleberg MO,without a computerised deck. We know the basic range of causes of this: incorrect screen angles, scanned image problems, registration - all checked. Now we are stumped. Can anyone help.

Author: Paul
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old-gmpx


Joined: 06/12/2006 00:45:36
Messages: -25
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moire patterns may be caused by slight regn. out. Check your lays.



Author: Sreekanth
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old-gmpx


Joined: 06/12/2006 00:45:36
Messages: -25
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Hello,

I am Mechanical Engineer working on single to six color Offset machines reconditioning & Installation, I hope I can be of help to u,

I am working some where near your country presently do contact with ur tel, I will try to solve ur problem.
Regards



Author: help to u
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old-gmpx


Joined: 06/12/2006 00:45:36
Messages: -25
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this problem may be caused by a thrust bearing or throw out bearing between the printing units. To find the source of the problem try process of elimination.
Determine the unit that is causing the problem if not pre-press related. If more than a 4 color press, skip that unit for a short term fix. Also run the press slower than normal and this will help hide the pattern.



Author: tj
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old-gmpx


Joined: 06/12/2006 00:45:36
Messages: -25
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This problem can be for many reasons and is fairly common all older machines.

1. Misregister
2. Sheet to sheet Variation
3. Excessive Dot Gain

If you have the option of moving to FM screening (instead of AM screening) that may be one sure way of avoiding this problem.

Good Luck and let me know if you make any progress.

Ravi




Author: Ravi Shroff
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old-gmpx


Joined: 06/12/2006 00:45:36
Messages: -25
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i have experieince on the MO and the thrust bearings can cause this proble. you might also try switching k and m angles if this appears in flesh tones.



Author: tp
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