Wohlenberg MCS 3 positioning error

Discussion in 'Cutters and Trimmers' started by JohannesausLinz, Feb 1, 2021.

  1. JohannesausLinz

    JohannesausLinz Member

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    At the outset, let me gratulate to this amazing specialists forum. I was extremely surprised to find such international and knowledgeable forum on this printing & finishing topic, really great.

    Secondly, I need to introduce myself: I am an 53 year old mechanical engineer. Now, I start to take over my fathers business, who invented/is producing since 40 years a special product, which is basically a PVC-film with a special pyramid surface, being imprinted while extrusion. Product is called "pyramid liner", a drawing aid, available globally eg. on Amazon. After giving it its special surface structure, we print a grid and logos etc. on the surface of the film. Therefore we use a Roland offset machine and cut the formats with a Wohlenberg MCS 2-TV.

    Thirdly, I seek some advice from you professionals: Our Wohlenberg shows the infamous positioning error - in automatic cutting mode, it frequently fails to hit the programmed value (eg 500mm) - stopping at 495 or so, and showing "positioning error" on bottom of screen. This happens every 3rd or 4th movement when running through the program.. My bright father found out that a repositioning attempt with manual pressure against the engine improves the situation and the machine finds back to the programmed position - he is simply pressing by hand against the formats while they are moving and this seems to help the machine to find the right position then.......

    After screening the forum, I found that the encoder might be faulty; also I saw that the machine factor for "stopping distance" possibly needs to be changed. How can I check the encoder? Any other tips from you cracks?

    Best regards from snowy Austria, Johannes
     
  2. JohannesausLinz

    JohannesausLinz Member

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    sorry for the stupid mistake: Its a Wohlenberg MCS 2-TV. It seems I canĀ“t change the headline of my topic, therefore I correct it here.....
     
  3. CHOCK

    CHOCK Senior Member

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    Hi sir:

    Attached is the link how you can test encoder easy :


    Hope you can do it.

    Blessing
     
  4. JohannesausLinz

    JohannesausLinz Member

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    Thanks a lot for the link, Chock! Will check that....first we do some lubrication check - maybe its just increased mechanical clearance due to age, or some underlubricated spindel etc. But the oszi-check might be next step then.
     
  5. CHOCK

    CHOCK Senior Member

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    Clean very well , and then LUBE.

    Finally, test the encoder with Oscilloscope.

    Blessing
     
  6. JohannesausLinz

    JohannesausLinz Member

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    wishing you a good day from Austria. Short update: Lubricated spindle - the positioning error became much less - and if it happens then no additional pressure has to be applied to come to right position at second try. Will keep in mind the osci test, but seems to be more mechanical issue.

    BR Johannes
     
  7. CHOCK

    CHOCK Senior Member

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    ok, thank you, test however if the spindle has a little Play.

    If is o.k, go to the test the encoder with the Oscilloscope.
     
  8. JohannesausLinz

    JohannesausLinz Member

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    Hi Chock, how are you doing? After having lubricated the spindle, it kept working without positioning error, this was fine. However today we got into trouble again: In operation, suddenly the TV monitor becomes black, then machine starts beeping and stops the operation. After disassembling front screen and looking into monitor electronics, it seems that monitor -or the board directly located close to monitor- has troubles. Any hints from your side to cure the issue? Are there any ways to test the electronic board of the tube, or the tube itself?

    Best regards from Austria, Johannes
     
  9. CHOCK

    CHOCK Senior Member

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    Hi sir:

    Will be a great idea, that you Reheating the complete board for Monitor : for Dry +Colder joint solder , and of course previously clean very well, and then Reheating, clean all connector in that section. You must check the CRT , is o.k.

     
  10. JohannesausLinz

    JohannesausLinz Member

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    Thanks Chock, will try that right away tomorrow! BR Johannes
     
  11. CHOCK

    CHOCK Senior Member

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    Ok.

    Blessings.
    @ing_dr
     
  12. JohannesausLinz

    JohannesausLinz Member

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    Hi Chock, resoldered the board but failed......whenever I connect the CRT board to the power supply, machine beeps and switches off. Machine is working also without the CRT but no measurement is shown.... also when I connect the board with the CRT tube disconnected, same happens. I guess that the tube is OK, but the board has internal shortcut. I will ask a friend (electronics engineer) to measure the board - maybe he finds a bad component which can be exchanged.....elsewise I have to search for exchange board.

    Have a nice evening!
     

  13. CHOCK

    CHOCK Senior Member

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    Ok Sir.

    Measure very well the Regulated Power Supply x Control Board in Tolerance:0.7% up or down.

    Blessings .
     
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