Refine jacket cracking

Discussion in 'Heidelberg Printing Presses' started by asem alsafady, Mar 15, 2018.

  1. asem alsafady

    asem alsafady Senior Member

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    Dear all,
    We are facing a problem in the new refine jackets (original parts). At SM102-10, SM 102-8 printing machines.
    After I have installed new jackets, one_two weeks of printing, the jackets cracked from the tail edge.
    On the past, I did this job many times without any problems.
    I used the special roller, and followed the steps carefully and checked the hollow using a dial gauge, the deviation was no more than 0.01mm.
    Any ideas will be appreciated.
    Thanks.
     

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  2. Andrei83

    Andrei83 Member

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    Perhaps you inserted pins with a distortion, or the lining leaf moved down?
     
  3. junker1984

    junker1984 Senior Member

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    If it is so that you followed prescribed procedure, this should not have occurred. Are all cracks at the outer edges of the cylinders as the one you've displayed? If so, the jacket could not have been installed true to the cylinder. Once I have jacket in place, and without fully tensioned, i use a dial caliper to check true run of it at lead and tail. If measurements are not the same, I will then pry the clamp at tail until I get equal measurements. Only then will I fully tension the jacket. Another step I take is, when fully tensioned, I lightly bounce a 13mm wrench across full width of lead and tail edge, listening that there is no variance in tone. Sadly, there is no fix for the damage that has occurred, other than new jacket. At the cost of these items, you really should pay a skilled and insured mechanic to do this, better yet, a factory authorized tech.
     
  4. mantman

    mantman Senior Member

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    Did you have registration issues?
     
  5. contractor

    contractor Member

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    Looks to me like you have over tensioned the screws on the tail edge especially the 2 outer ones can rip the jacket if you put too much tension on them.
     
  6. asem alsafady

    asem alsafady Senior Member

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    Thanks for all of you,
    Junker, actually, I had an issue with cracking from edges, the other from edges and middle. But I used the dial gauge with the arm and magnet, and I don't know what do you mean by dial caliper and how to use it?
    Mantman, I don't have problems with registration at all.
    Contractor, I am sure ofthe screws tension, not more than 5Nm.
    Thanks for all of you for your interest.
     
  7. junker1984

    junker1984 Senior Member

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    Dial caliper.
     

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  8. exheidmech

    exheidmech Senior Member

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    Newly installed jackets will break because they were improperly installed. To install a jacket properly you need a pressing bar. This is the only way to ensure that the jacket is fully seated in the lead edge and tail edge clamps. If a pressing bar is not used to seat the jacket into the lead and tail clamps especially on a SM102, it will break. It is also possible that the cylinder under the jacket was not cleaned properly or that the jacket used is not a Heidelberg jacket but usually it is the technique used when installing a jacket which will determine the lifespan of that jacket.
     
  9. asem alsafady

    asem alsafady Senior Member

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    I have already used the pressing bar!
    But please Junker, how can I use the dial caliper in the procedure, and what shall I measure.
    Many thanks.
     
  10. junker1984

    junker1984 Senior Member

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    We all have our variants in doing particular jobs, Asem, and my use of the caliper is just an extra step I take to be comfortable with the installation. Since you say you have a split in the middle of one of the jackets, it’s unlikely the cause was from being skewed. But for the ones split on the ends, it could be. As to how I check true run with the caliper. I use the inside measuring faces (tangs) by measuring the distance from the bottom of the chamfer of the undercut to the edge of the jacket, lead and tail. Obviously, the bottom of the chamfer is not a point that you can be sure you’re getting a true measurement, so I take 3 or 4 measurements to be sure of the value. Good Luck
     
  11. exheidmech

    exheidmech Senior Member

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    What type pressing bar are you using? Are you using it on both the lead and tail edge?
     
  12. asem alsafady

    asem alsafady Senior Member

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    Yes, exheidmech. I know just one type of pressing bars, and actually I don't know any other types! And I used the pressing bar on both lead and tail edges.
    Many thanks Junker for the great information, I hope I can did it.
    Regards.
     
  13. exheidmech

    exheidmech Senior Member

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    Since the Heidelberg pressing bar on the SM102 is a proprietary tool and not supplied with the machine when new, it is very rare to actually see an independent mechanic or customer use and actual Heidelberg pressing bar for SM102. It is for this reason why I asked you which pressing bar you are using. Its not uncommon to see homemade pressing bars used by independents and customers alike. Also, I have seen customers use letterpress furniture to knock in the lead edge and do nothing with the tail edge pretty much ensuring a cracked jacket. I am glad that you have no further issues with your jackets and that you got it all sorted out.
     
  14. asem alsafady

    asem alsafady Senior Member

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    Actually, I have the original pressing bar, and I have used it many times before.
    Yesterday, I have installed a new jacket very carefully, then I checked with the dial gauge (+0.01) was the maximum deviation.
    Many thanks my friends.
     
  15. mantman

    mantman Senior Member

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    I still dont understand what you measure with the dial gauge -and how :confused:-
     
  16. exheidmech

    exheidmech Senior Member

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    Your not the only one...
     
  17. junker1984

    junker1984 Senior Member

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    Ancient Chinese secret...but really, I'm not sure I could have been more clear.
     
  18. exheidmech

    exheidmech Senior Member

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    Hey, as along as the end result is a successful installation, it doesnt matter much how it gets done. Like you said, we all have our own way of getting jobs done. I would love to see how you measure "true run from lead to tail" with a dial caliper.
     
  19. asem alsafady

    asem alsafady Senior Member

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    When you finish installation, put a magnet at the frame with a long rod and a dial gauge.
    Try your best to make it perpendicular to the cylinder, make some tension, make the pointer to zero. Test if there are any hollows. The range is 0.01mm at the lead edge, 0.02mm at the tail edge.
     

  20. junker1984

    junker1984 Senior Member

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    Many years ago, I was finishing an installation of a jacket and realized I’d left my dial and base behind. I chose to complete the install w/o it, realizing I could be on the hook for $2K if I messed up. Got the jacket tensioned up, but by tapping with a 10mm wrench across lead and tail, found one side sounded a bit hollow at the tail. Because I was truly confident the jacket was fully seated in the tail clamp, I wondered if the jacket may be a bit skewed. I pondered how I could prove it, and came upon the method I’d described. Keyword is distance. I measured the distance of the edge of the jacket to the base of the chamfer of the undercut with the tang side of my caliper, first at lead and then at tail. I’d found a variance of .010”, and so loosened tail clamp a bit and nudged it the direction I needed to true up the skew. I’ve not used a dial since, and have not had any cracked jackets. Coincidence, maybe? Not sure, but I stick with what works for me.
     
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