Standard Finishing
4Over

Announcement

Collapse
No announcement yet.

horizontal banding

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • horizontal banding

    We have been having this problem from time to time...

    On our 4 color 40" Heidelberg press we have noticed this problem is evident from time to time. Please view attached file.
    The banding shows up in different places on different press runs. Some times its in the middle some times in more toward the lead edge of the sheet (gripper side). This problem occurs through the whole run. Any input will be greatly appreciated. Thanks!
    Ernie

  • #2
    Re: horizontal banding

    apart from rollers - which always seem uniform - sometimes its a ghost of the gaps in the form or where the colour bars are

    Comment


    • #3
      Re: horizontal banding

      i cant see any problem with the sheet, could somebody point out what im looking at and where?

      Comment


      • #4
        Re: horizontal banding

        The sheet is printing nearly full coverage of cyan, a good bit of magenta too. There are bands showing up on various jobs, with heavy coverage, in different places of darker ink. You monitor may be adjusted different than ours, that may be why its not visible. The top half of the pic is darker than the bottom half. This is a small section of a 23x35 sheet BTW

        Edited by: Ernie on Apr 16, 2008 9:46 AM

        Edited by: Ernie on Apr 16, 2008 9:47 AM
        Ernie

        Comment


        • #5
          Re: horizontal banding

          Hi Ernie,

          i see the issue now. Firstly its very difficult to look at a sheet and cure the issue without looking at the rollers and press running. To rule out some options get your operator to drop the dampers off and see if the color shift/ banding is still on the sheet after a dry solid is run. If it is then check all ink form to steel strips, most of the ink is added to the plate with the first two inkers, the fourth and third do very little other than smooth the ink out. My guess is a dry solid will be without these bands. If so then check all damping settings, check all bearrings and journals for play and correct if neccessary.
          If this does not work take out the fourth inker and see if it helps, ive seen this issue cured when this happens. Try the above and at worst we will know weather its inker or damper related and maby get closer to a soloution for you.

          Paul

          Comment


          • #6
            Re: horizontal banding

            Cool, thanks! Ill pass that info on.
            Ernie

            Comment


            • #7
              Re: horizontal banding

              It could be a starvation issue. You are getting light heavy light heavy effect from running too low a sweep setting on your ink fountain roller. Try turning up the sweep.

              Are you running your dampening system integrated or non-integrated?

              Comment


              • #8
                Re: horizontal banding

                I know a guy who runs a Komori that had an issue like this. During the run the magenta would drop off the sheet, four or so sheets would be fine the next would have no magenta or it would be at density for the first half of the sheet and not the second. I'm not sure if this accurately describes what's happening to you, but what it turned out being was simply calcium build up in the rollers. The guy got a calcium wash from Bocher for when he rinses the rollers and it's been fine. Some rollers are more susceptible than others. Sorry, that's all I have to offer.

                Comment


                • #9
                  Re: horizontal banding

                  It could be gearing vibration. Is your press shafted and do you use gap blankets? If so is the Banding really bad at the beginning of the print of a single copy and goes away?

                  Comment


                  • #10
                    Re: horizontal banding

                    Try to re-set cylinder pressure parallel for Blanket and Plate cylinder. Use calibrated paper for gap and make a test without fountain water. If banding persist, problem is Inking unit. If not, problem is dampening system. Check for arms and bearing hold of system.
                    When run test, change blanket and fountain solution (ph and TDS controlled) for ensure correct reading.

                    Comment

                    UltimateDuploSmartsoft (Presswise)Standard FinishingKBA4Over
                    KBAKBA

                    What's Going On

                    Collapse

                    There are currently 3319 users online. 59 members and 3260 guests.

                    Most users ever online was 6,151 at 11:36 AM on 11-17-2017.

                    Working...
                    X