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Re: [PPLetterpress] Windmill Registration Problem

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  • Printer
    Every-other-sheet misregistration is a common scenario. When I can t fix something by adjusting this or that, I go back to Square One, so to speak, by running
    Message 1 of 11 , Oct 4, 2004
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      Every-other-sheet misregistration is a common scenario. When I can't fix something by adjusting this or that, I go back to Square One, so to speak, by running a sheet through in slow motion. That is, I turn on the press, and have the sucker bar pick up a sheet and let the gripper bar grab it. Stop the press right at the point where the gripper bar has grabbed the sheet, but before it has started to swing in to the platen. Now shut off the motor and let the flywheel stop spinning. Now you can open the hatch on the flywheel's safety cover, engage the clutch, and start turning the press by hand. Watch the sheet carefully as it is being brought in to the side guides, and look for places where the sheet is getting hung up or misaligned. What I would look for is:
      Is the sheet too close to/too far from the bottom guides?
      Is one end of the sheet slipping off the bottom guide?
      Are the bottom guides aligned well with the bottom of the platen?
      Does the front of the sheet get pulled against the front guide before the gripper releases it, or is it released just a little in front of that guide?
      Does each gripper arm grab the same amount of paper, or is there a big difference? This would indicate that one arm is way out of alignment.

      Because you are getting crookedness, I would suspect that one end of the sheet isn't landing on the side guide, and maybe is slipping between the guide and the platen. There is a little widget that slides onto the track under the bottom edge of the platen that is made for this kind of situation- it keeps the sheet a little off the platen until the side guides are up and in position. Alternatively, you can cut a little triangle flap in the tympan and curl the point up a bit, at the end where the sheet is slipping down. This pushes it off the platen just enough to catch the side guide.

      Good luck with this. These things can be really frustrating and each windmill has it's peculiarities, in my experience. But you can figure out a lot when you turn it by hand and look at what is going on carefully. It may not be the gripper arms causing your problem, in the end. Cast out all preconceptions and put your trust in empirical observation!! ;^)

      Joel

      Joel Benson
      Dependable Letterpress
      San Francisco
    • almoprint
      I had similar problem a while back. One of the gripper bars had a tiny spot of adhesive on it. I assume it was a remnant of a die cutting job. After cleaning
      Message 2 of 11 , Oct 4, 2004
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        I had similar problem a while back. One of the gripper bars had a
        tiny spot of adhesive on it. I assume it was a remnant of a die
        cutting job. After cleaning it off the register problem went away.
        The hair I pulled out while trying to solve it, has not however, come
        back! Hope this helps you.

        Mike
      • Keith Berger
        Wow, you all made for a good Monday!!! Although I didn t ink up, I did watch the card in slow-mo and I did notice the tail end of the card was going over top
        Message 3 of 11 , Oct 4, 2004
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          Wow, you all made for a good Monday!!! Although I didn't ink up, I did
          watch the card in slow-mo and I did notice the tail end of the card was
          going over top of the [ fly wheel side] pin. So I put a longer pin in
          the guide and it looks to be better. Tomorrow I will ink up and see if
          it PRINTS better, that will be the real test.

          I will keep you posted.

          Thank You!!!!

          Keith


          On Oct 4, 2004, at 3:03 PM, Printer wrote:

          > Every-other-sheet misregistration is a common scenario.  When I can't
          > fix something by adjusting this or that, I go back to Square One, so
          > to speak, by running a sheet through in slow motion.  That is, I turn
          > on the press, and have the sucker bar pick up a sheet and let the
          > gripper bar grab it.  Stop the press right at the point where the
          > gripper bar has grabbed the sheet, but before it has started to swing
          > in to the platen.  Now shut off the motor and let the flywheel stop
          > spinning.  Now you can open the hatch on the flywheel's safety cover,
          > engage the clutch, and start turning the press by hand.  Watch the
          > sheet carefully as it is being brought in to the side guides, and look
          > for places where the sheet is getting hung up or misaligned.  What I
          > would look for is:
          > Is the sheet too close to/too far from the bottom guides?
          > Is one end of the sheet slipping off the bottom guide?
          > Are the bottom guides aligned well with the bottom of the platen? 
          > Does the front of the sheet get pulled against the front guide before
          > the gripper releases it, or is it released just a little in front of
          > that guide?
          > Does each gripper arm grab the same amount of paper, or is there a
          > big difference?  This would indicate that one arm is way out of
          > alignment.
          >
          > Because you are getting crookedness, I would suspect that one end of
          > the sheet isn't landing on the side guide, and maybe is slipping
          > between the guide and the platen.  There is a little widget that
          > slides onto the track under the bottom edge of the platen that is made
          > for this kind of situation- it keeps the sheet a little off the platen
          > until the side guides are up and in position.  Alternatively, you can
          > cut a little triangle flap in the tympan and curl the point up a bit,
          > at the end where the sheet is slipping down.  This pushes it off the
          > platen just enough to catch the side guide.
          >
          > Good luck with this.  These things can be really frustrating and each
          > windmill has it's peculiarities, in my experience.  But you can figure
          > out a lot when you turn it by hand and look at what is going on
          > carefully.  It may not be the gripper arms causing your problem, in
          > the end.  Cast out all preconceptions and put your trust in empirical
          > observation!!  ;^)
          >
          > Joel
          >
          > Joel Benson
          > Dependable Letterpress
          > San Francisco
          >
          >
          >
          >
          >
          >
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        • RoyVM@aol.com
          Check the rubber inside the gripper, be sure its clean. If it has been replaced with vinyl tape (electrical or bookbinding) which can be and is often done,
          Message 4 of 11 , Oct 4, 2004
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            Check the rubber inside the gripper, be sure its clean. If it has been
            replaced
            with vinyl tape (electrical or bookbinding) which can be and is often done,
            make sure it is
            not sticky.

            Make sure the gripper is properly holding the stock. Bring a sheet into the
            gripper,
            stop it as the gripper enters the press and pull on each side of the sheet to
            make
            sure the bite is even and adequate. . The gripper pressure can also be
            adjusted on each
            individual arm.

            If you are not using register pins on the guides, I suggest you do. The
            guides with
            the flat lip do not always catch the sheet when it is dropped.

            Decurl the stock. If the curl is up it can fall over the guide specially at
            the tail of the
            sheet. Use a longer pin at the rear of the sheet if possible. It also might
            be necessary
            to slightly bend the register pins open so the sheet will not override them.

            Check the bite on each gripper arm. Bring a sheet up with the suckers until
            the gripper
            closes on it. I then draw a line along the gripper edge. Do it to each arm.
            If the bite is
            considerably different between arms, it may be necessary to force them into
            alignment.
            I would not attempt this yourself, but a Heidleberg serviceman with windmill
            experience
            usually has a long bar to accomplish this.

            You may be running the press too slow for the momentem of the sheet to reach
            the
            sheet stop. I have found also that is is often necessary to move the stack
            side guide
            about 1/8" to 1/4" further to the right than the adjustment for the brass
            guide stop.

            I have also found that too much speed with certain types of stock, will cause
            the stock
            to bounce back from the front guide, after it is released.

            I currently have three 10 x 15 windmills and they are all different. No two
            run exactly the
            same.

            Good luck,

            Royvm


            [Non-text portions of this message have been removed]
          • Fritz Klinke
            The register pins are called lay pins or guides, and come in 5 different lengths. They are still made by Heidelberg and we stock them. Fritz ... From:
            Message 5 of 11 , Oct 4, 2004
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              The register pins are called lay pins or guides, and come in 5 different
              lengths. They are still made by Heidelberg and we stock them.

              Fritz

              ----- Original Message -----
              From: <RoyVM@...>
              To: <PPLetterpress@yahoogroups.com>
              Sent: Monday, October 04, 2004 11:06 PM
              Subject: Re: [PPLetterpress] Windmill Registration Problem


              >
              > Check the rubber inside the gripper, be sure its clean. If it has been
              > replaced
              > with vinyl tape (electrical or bookbinding) which can be and is often done,
              > make sure it is
              > not sticky.
              >
              > Make sure the gripper is properly holding the stock. Bring a sheet into the
              > gripper,
              > stop it as the gripper enters the press and pull on each side of the sheet to
              > make
              > sure the bite is even and adequate. . The gripper pressure can also be
              > adjusted on each
              > individual arm.
              >
              > If you are not using register pins on the guides, I suggest you do. The
              > guides with
              > the flat lip do not always catch the sheet when it is dropped.
              >
              > Decurl the stock. If the curl is up it can fall over the guide specially at
              > the tail of the
              > sheet. Use a longer pin at the rear of the sheet if possible. It also might
              > be necessary
              > to slightly bend the register pins open so the sheet will not override them.
              >
              > Check the bite on each gripper arm. Bring a sheet up with the suckers until
              > the gripper
              > closes on it. I then draw a line along the gripper edge. Do it to each arm.
              > If the bite is
              > considerably different between arms, it may be necessary to force them into
              > alignment.
              > I would not attempt this yourself, but a Heidleberg serviceman with windmill
              > experience
              > usually has a long bar to accomplish this.
              >
              > You may be running the press too slow for the momentem of the sheet to reach
              > the
              > sheet stop. I have found also that is is often necessary to move the stack
              > side guide
              > about 1/8" to 1/4" further to the right than the adjustment for the brass
              > guide stop.
              >
              > I have also found that too much speed with certain types of stock, will cause
              > the stock
              > to bounce back from the front guide, after it is released.
              >
              > I currently have three 10 x 15 windmills and they are all different. No two
              > run exactly the
              > same.
              >
              > Good luck,
              >
              > Royvm
              >
              >
              > [Non-text portions of this message have been removed]
              >
              >
              >
              >
              >
              > Yahoo! Groups Links
              >
              >
              >
              >
              >
              >
              >
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