Gto impression/gauge problem

Discussion in 'Heidelberg Printing Presses' started by mantman, Oct 3, 2019.

  1. mantman

    mantman Senior Member

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    Hello, recently i printed a rather difficult paper and had to max out impression pressure, but i noticed that in some PU`s the arrow went further away from -0,2 while others did not even reach the gauge max.
    So i loosend the screw that keeps the gauge, turned knob to -0.2 and tightened screw again.
    Out of curiosity i used a filler of 0.20 with impression on to see the gap between blanket/impression and saw that in PU 4 -yellow- DS filler would not go in while OS filler would slip in quite easily. That happens at the rest of PU`s, though some at OS than DS.
    I reseted them at 0 with 0.35 feeler for now just wondering if my pressures have mech issues -bent journals? impression knob out of sync etc-, machine is GTO 52 perf 4c waterless
     
  2. turbotom1052

    turbotom1052 Senior Member

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    you need to print break away dry solids and then recalibrate your gauges all the same. Do this with a gloss coated sheet, and calibrate gauges to allow for readings that can print to the thinnest uncoated sheets. Im assuming that the blankets and plates are printing at the correct heights as measured with a packing gauge.
     
  3. mantman

    mantman Senior Member

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    Plates are 0.15mm without any kind of underlay, as for blanket 1.90-1.95 and i use finito packing 1.15mm so i am over by 0.10.
    It seems a lot of pressure but it works a lot better like this than the previous setting of -0.05 or level with bearer ring, i get a whole lot of better results considering the drying of ink and printing solids with no slurring
     
  4. turbotom1052

    turbotom1052 Senior Member

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    total squeeze between plate and blanket should be between .004" and .005" How you get there is less important than actually getting there. This will allow you to print consistent with previous printing, will allow for better plate and blanket life, and minimize streaking due to excessive plate to blanket pressure.
     
  5. mantman

    mantman Senior Member

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    Hmm streaking from excessive squeeze this gives me much thought since i do have streaking, though not always visible. Plate life is not that much of an issue as i usually print 500-2000 sheets max per job. Thing is, finito packing is a lot consistent, compared to paper manila packing. Also it can handle smashing of blankets and the change of blankets for envelope occur much faster. Thank you for your input mastertom :)
     
  6. turbotom1052

    turbotom1052 Senior Member

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    don't know what the cylinder undercuts are for the GTOs but Id guess and say that your running .008" thick plates. If you can get the plates even with the plate cylinder bearers, and then pack your blankets to measure .004" to .005" over the blanket bearer height then you will have the required plate to blanket squeeze. All that remains would be to hope that there is enough blanket to impression cylinder pressure to print lightweight porous stocks. Once your able to do all that its then just a matter of re calibrating your dials to match the sheet thickness.
     
  7. mantman

    mantman Senior Member

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    Here is my formula:
    Plate cylinder undercut 0.03 - plates used 0.15=+0.12mm
    Blanket cylinder undercut 3.00 - (packing 1.15 + blanket 1.95=3.10)=+0.10
    Squeeze 0.22
     
  8. turbotom1052

    turbotom1052 Senior Member

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    here in the U.S. we work in imperial. When I do the metric to imperial conversion of your total plate to blanket squeeze I come up with .008" of squeeze. This is more than the recommended .004" to .005". I believe this could be the cause of your streaking. The only issue that remains to be seen is WHY your press is set up this way? Are you just following what the guy before you did? Perhaps you arrived at that excessive plate to blanket squeeze because even with the impression setting maxed out, you weren't getting the ink into the thin porous papers??? Either way if I were running the press id start by adjusting plate to blanket packings to arrive at no more than .005" total squeeze as measured with a packing gauge. Once I got the plate to blanket correct id be looking to do break away solids to see if the blanket to impression cylinders were parallel to each other. The impression gauges should be ignored at this point. Once you get the blanket and back cylinder printing both parallel and with the required amount of "KISS" impression, then, and only then would I calibrate the gauges to the thickness of the stock your testing on. Something worth mention is that you also need to be sure that the plate cylinder and blanket cylinder are parallel to each other. Im thinking but not really sure when it comes to GTO if there are provision available to the operator for setting the plate to blanket to spec. My guess is that there aren't and would require a tech. Im sure Steve aka Junker could help you with that one.
     
  9. junker1984

    junker1984 Senior Member

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    I'm feeling the pressure now, Tom! OK, so though I spent my productive years as a tech and having never been a pressman, I always hesitated to correct a customer's plate/blanket packing protocol unless the parameters used were so out of whack that going back to basics was the best place to start. By the book (operator and service manuals) the proper packing should have you arrive at .004"-.006" squeeze for compressible blanket and .004" for noncompressible. Running a standard .008" plate and packing the blanket to bearer height would get you to standard. Given Mantman is running .15mm (.006") plates, adjustments to blanket packing or possibly a .002" underlay at plate would be required? I am more than willing to stand corrected on this, as I've no experience with .006" plates used on GTO. That being said, as Tom mentioned, the key here is to prove parallelity of cylinders and prove that there is no damage (caving) of cylinder surfaces or bent journals. This would typically be done by running the breakaway dry solids. However, I see a sticky wicket here, as Mantman has altered the indicator arrow positions, without knowing if bearer pressure settings are correct. The best move at this point would be to do the breakaways, to check for possible damage at cylinder surfaces and journals. Keeping in mind we're skipping a step, that being checking and setting bearer pressure settings, which is a whole new ballgame.
     
  10. turbotom1052

    turbotom1052 Senior Member

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    So Steve the standard undercut of a GTOs plate cylinder is app. .004" to .005". Id think that a .002" paper packing underlay on the plate cylinder would get messy, not to mention time consuming. When I say messy I'm thinking about lots of sticking at such a small caliper. Do they even make polyester permapack sheets in .002" thickness? Unless they need to match print length on this GTO with print length of another press wouldn't it be preferred to just make it up under the blanket? Even if print length was an issue to watch out for, I would think that in a GTO format a couple of thousandths would be a spit in the ocean, even at full sheet length.
     
  11. junker1984

    junker1984 Senior Member

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    My biggest concern is condition of cylinder integrity, and second, bearer pressure settings. As far as packing issues, that's an area of expertise I leave to you, Tom.
     
  12. mantman

    mantman Senior Member

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    Oook then, as far i can see, i managed to open pandora`s box :) -wall of text will crit you for...a lot-

    For quite some time, previous printer used manilla packings -me as well- which gave dubious results.
    "Dubious results?" Que? Why? GTO`s print envelopes too as you well are aware and the time i lose changing blankets AND packings -i even had 4 sets of packings especially for envelopes- combined with the occasional smashed up blanket(s) change manila packings too, so my impression changed all the time, while with perma packing i have a consistent impression, ergo TVI too. Now with perma pack smashing is not always visible or at least i switch blanket good to go fast fast

    When i changed to perma packing at blanket, which sadly is NOT the correct height of 1mm -0.04- but 1.15mm or 1.10mm -0.045/0.043- since there is just one provider of finito packing -to be honest there could be more but its NOT my job to search for others- and the prospect of ordering from mother company is well...not an option. Also registration took a turn for the best compared to manila packing, and to be honest i am very comfortable with this setting -wrong i know but it works for me and the company-. Print length is corrected with web growth of images from RIP.

    I print silk coated papers mostly but thin and porous papers, especially with full color background is a nightmare for me, that could be an issue with ink being very tacky and unable to penetrate pores of paper.
    "Ok here is your solution buddy boy...tack reducer". Well i CANT use reducer cause i might get toning of plate -WATERLESS printing- and it totally messes up my traps/tvi`s etc. let alone drying times.
    "Very well you big baby, change your ink supplier then!" Guess again...only ONE supplier of these inks by Sunchemical.
    The only way i can change the viscosity of ink is via reducing the cooling of ink train along with room temp -well room not really we try to keep it steady at 24celsius but summer time we get outside 36 to 40 degrees of celsius and inside is 25 or 26-

    As for plate blanket pressure, i dont have a clue if they are correct -come to mention it, i did it in the past and it looked ok-

    You see that i am trying to make two loose ends 200 miles apart come to meet, in conditions not even close to "optimal".

    All things considered, your input in this forum, is gold as they made me better at my work and i thank you deeply!
     
  13. junker1984

    junker1984 Senior Member

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    You mention waterless technology, Mantman. Is this an old GTO-DI?
     
  14. alibryan

    alibryan Senior Member

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    Toyo makes a waterless ink that imo is superior to Sun Chemical’s, I don’t know if you can find it in Greece, or not.
     
    Last edited: Oct 10, 2019
  15. mantman

    mantman Senior Member

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    Yes junker its a GTO-DI though we are not using the DI tech we make plates with CtP,
    Other brands I used for a while was Sakata with good results and Toyo only Magenta, but i dont want to mix different brands.
     
  16. Travis Young

    Travis Young Member

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    First time reply to a post. Hope I don't sound like a know it all.........
    Might need to go back a step or two here.
    Generally speaking with a GTO, it's only the basic stuff that causes problems.
    Correct me if I'm wrong, but oversize blanket packing shouldn't effect the fit or print length.
    If you're having image problems, and your blanket is overpacked, it will most likely be because there's too much pressure between plate and blanket. This increased pressure could potentially be causing premature wear on the press.
    Additionally, overpacking the blanket and cranking the pressure all the way up is probably pretty hard on the machine in the long term as well.
    I'm guessing when you stop the press it prints on the impression cylinder.
    Germans are really good at making stuff. If they say pack it with 1mm, then it's probably best to pack it with 1mm.
    I'd fix that first.
    Back all the pressures off to 0.00 and run a dry solid (it's waterless, they're all dry!).
    Incrementally wind them in until you get an even image and adjust the red arrows to suit. It's a GTO, it's not that critical.
    This may sound ultra simplistic and I'm not sure if you can do it with DI presses, but can you turn the sweep right up and close the blade a bit so the machine is working the ink in the duct and reducing its viscosity.
     
  17. mantman

    mantman Senior Member

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    Your guess is incorrect about printing on impression cylinder when the machine stops, as that is affected by the timing of lifting the impression
    When you work ink you change the thixotropy until at certain point but you cannot change viscosity with increased sweep.
    I went over the PRESSTEK GTO-DI manual and stated, you start by even blanket bearer due to dry offset printing, extra pressure is required. Good results can still be achieved by going over .003. Squeeze was .055, dont remember the plate they used

    Its a GTO? Its a printing PRESS, what you feed in terms of plates/ink/water/paper you will get that result. Poor ink/water balance wash out jobs, poor plates tonal increases or biases towards certain colors -reddish, bluish etc-, poor paper more washups, drying times, and a list mile long
    Meaning you can print equally good with a SM 102CD -if not better- or Roland 700, if your prepress makes GOOD plates -what tom said earlier-. In my 20 years of experience and worked with large presses -4 col Rekord-, medium presses -2 col SM72- and now smaller -4col GTO-, the only important difference between them is the much lower makeready times with newer models.
     
  18. Travis Young

    Travis Young Member

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    That's interesting about the timing. Would definitely contribute. Do you know how to adjust it?
     
  19. mantman

    mantman Senior Member

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    This is a mechs job ;) -junker standing tall in front of the rising sun, wrench in right hand, greasy left hand with hammer and a determined scowl oh forgot the cigar, kinda like Nick Fury-
     

  20. junker1984

    junker1984 Senior Member

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    Ha! Love the visual!!
     
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