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Press is printing wide NEED HELP!!!

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  • Press is printing wide NEED HELP!!!

    Hey guys, got a problem....

    one unit on one of our presses is printing too wide (horizontal stretch).

    we put on some grid plates... get the middle to fit its hanging out as it goes out to the edge.

    We put on new blankets, tried different stock and we are lost on how to fix this. I know that packing can effect the vertical stretch, but ive never seen a horizontal stretch
    any help is greatly appreciated. Thanks!

    Edited by: Ernie on Apr 1, 2008 11:00 AM
    Ernie

  • #2
    Re: Press is printing wide NEED HELP!!!

    If you changed blankets to fix this problem, did you also change the packing? If you did I would look at your plate clamp and also the gripper transfer and pressure. Something is distorting some where!

    Is this a 2 color 4 color press? Perfector?

    Throw us a bone here man

    8-}

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    • #3
      Re: Press is printing wide NEED HELP!!!

      Double check the grain of the packings, operator could have cut them incorrectly. What model and year machine ? Are you using packing on plate cyl ?

      Comment


      • #4
        Re: Press is printing wide NEED HELP!!!

        >one unit on one of our presses is printing too wide (horizontal stretch).

        Is this the last, or one of the middle units? Is the stretch the same amount at the gripper as at the tail? Is the grain of the printed stock parallel to the cylinder? How thick are the lines in the grid? Using that, estimate how much is the stretch from end to end on the sheet.

        Edit: What weight is the stock? Coated or uncoated?

        Edited by: Al Ferrari on Apr 2, 2008 11:08 AM

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        • #5
          Re: Press is printing wide NEED HELP!!!

          We tried several different stocks coated and uncoated, grain short and grain long. We run packing under plate and blanket, we put on new packing as well. Its a 2 color press 80s Heidelberg sordz (not a perfector), printing is stretched on first unit, the second unit measures true (closest to delivery side). We tried turning the impression off the second unit and the problem still was evident. Stretch is uniformly wider. Lines are .5 pts thick.

          Noticed it on a job and put on the grids to have a better idea of what was going on. Total stretch is about 1/32" -1/16" overall

          Edited by: Ernie on Apr 2, 2008 12:42 PM
          Ernie

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          • #6
            Re: Press is printing wide NEED HELP!!!

            Does it change with more or less squeeze ?

            Do you have a dial indicator to check the cylinder ?

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            • #7
              Re: Press is printing wide NEED HELP!!!

              >We tried several different stocks coated and uncoated, grain short and grain long.

              You should have seen some difference between these various stocks. The coated stocks should be more stable compared to uncoated. The grain long stocks should show the problem quite a bit less than the grain short stocks, if both are fed with the long dimension parallel to the cylinder axis.

              > We tried turning the impression off the second unit and the problem still was evident.

              You should also try turning off the first unit and printing with the second. Then compare the stretch on grain long coated sheets from printing with only the second unit to those from printing with only the first unit. They should both show about the same problem if they are both correctly packed. Why? Because that's what happens to paper when it is squeezed in any printing unit. But in multi unit printing, the second and subsequent units have much less of an effect on the stock. This is a well known common problem.

              >Stretch is uniformly wider.

              I am surprised that it is not significantly more towards the tail. Are you sure about this? This is called the "fan out problem".

              >Total stretch is about 1/32" -1/16" overall

              That seems like a lot, but you don't say what size press sheet you are testing with.

              Have you had this press for a long time and it just started to happen, or are you evaluating the press prior to purchase?

              Al

              Edited by: Al Ferrari on Apr 2, 2008 10:14 PM

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              • #8
                Re: Press is printing wide NEED HELP!!!

                Most of out sheet sizes are around 23x35. We have had this press for 10-15 yrs. Its correctly packed, we checked the packing with a gauge. The impression has been checked. Im sure the stretch is the same at the lead edge, middle of sheet and tail edge. According to the pressroom super all the stocks were printing wide. Coated stocks werent as bad, but still printing wide. They didnt try turning off the units and measure individual units, just did that with the unit thats having the problem and it was the same.

                I appreciate all the great responses guys.

                Edited by: Ernie on Apr 3, 2008 8:27 AM

                Edited by: Ernie on Apr 3, 2008 8:28 AM
                Ernie

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                • #9
                  Re: Press is printing wide NEED HELP!!!

                  >They didnt try turning off the units and measure individual units, just did that with the unit thats having the problem and it was the same.

                  But Ernie, what you wrote earlier was: "We tried turning the impression off the second unit and the problem still was evident."

                  Those two statements are contradictory.

                  Is this a 2 or 4 color press?

                  >We have had this press for 10-15 yrs.

                  Was there a time when this "problem" did not occur?

                  I am suggesting that you are incorrectly concluding that only the first unit stretches the paper. You need to test each unit separately, and compare the printed image length against the plate image length:

                  For each unit, take a sheet printed only on that unit, and cut it all the way across the tail so that the grid lines bleed (cut it with a straight edge and razor, not under cutter clamp pressure) and line up that bleed edge of the sheet on the corresponding part of the plate. I think you would find that all units have this stretching effect on the paper.

                  Al

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                  • #10
                    Re: Press is printing wide NEED HELP!!!

                    units (plural), we measured the unit that was having the problem individually, but not the unit thats printing true. The unit printing true was measured with both units on impression.
                    2 color press as stated above. This is a new problem that was noticed during a process job, it has never occurred before. We put the grid plates on to try to figure out what was happening.

                    Edited by: Ernie on Apr 3, 2008 10:49 AM
                    Ernie

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                    • #11
                      Re: Press is printing wide NEED HELP!!!

                      >The unit printing true was measured with both units on impression.

                      Well my point is that this is a misleading measurement. The second unit only appears to be printing true because the first unit already stretched the paper about as much as it is going to stretch. If you would print with just the second unit, you would find that it also stretches the paper about as much as the "problem unit".

                      Anyway, has the problem continued? Are you still using the press, for 4 color process work?

                      Al

                      Edited by: Al Ferrari on Apr 3, 2008 3:57 PM

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                      • #12
                        Re: Press is printing wide NEED HELP!!!

                        Press super said they backed off impression on the both units until they were barely printing and we still had horizontal stretch on the 1st unit.

                        We also tried #80 enamel, #50 offset and #80 cover.

                        Edited by: Ernie on Apr 4, 2008 10:37 AM
                        Ernie

                        Comment


                        • #13
                          Re: Press is printing wide NEED HELP!!!

                          Ernie
                          I have seen something like this - when we were running a full out sheet - It was caused by ink build up on the impression cylinder (because we normally run smaller sheets)

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                          • #14
                            Re: Press is printing wide NEED HELP!!!

                            our mozp had a paper growth compensator. does the sordz have this? where is the dial set +3 to -3. it is on the feed transfer/ranger drum. little dial in the center. we had all kinds of trouble with this. did some one recently set the paper thickness on this drum? idle hands will do more harm than good. the sheet will spead on the first unit and straighten out on the second. someone mentioned to dial indicate the cylinders. this is when you attach an articulating arm usually magnetic to the side frame. the end of the arm has a level dial just like the 3 dials on the packing tester. you pull the plates and blankets off and check the entire circumference of the cylinder at the ends and in the middle. with out the dial indicater you could pull dry solids and do breakaways. then reduce the packing on the blanket until it breaks away from a solid on the plate and see if it is even over the entire blanket. I would bet the problem is in the feed drum. get heidelberg out to look at it. it will cost you $. but a good mechanic should find the issue quickly.

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                            • #15
                              Re: Press is printing wide NEED HELP!!!

                              Hi

                              as you havent posted again recently i guess you still have this problem. Peter makes a good point, ++if your printing to wide the surface area of the impression compared to the blanket must be larger+this can only be caused by the sheet not lying true under impression, in peters case its due to the sheet having to sit on the surface of the of the ink instead of on the cylinder itself, this difference adds to the print length. This could also be caused by a small packing sheet being under the plate cylinder causing a crowned surface to the cylinder and thus increasing its horizontal length. The same could also be said if the impresson cylinder has had water or solvent penetrate the edges causing the material to either swell or rust, i would suggest checking the cylinder surface benneth the impression jacket. This seems a logical path to follow and its not noted above. My last point is that you dont mention TVI being increased on this unit which would rule out and bearing or sheet transfer issues, is this right?

                              Paul

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