Plate movement

tape

For those of you that use Patmag bases, what do you do to keep your steel-backed plates from moving? I have a pretty large solid – about 15″ x 4″ – that I’m running and I discovered, upon running the second color, that the plate had continually moved throughout the run. Makes registration a damn pain, that’s for sure.

Anyone try spray mount? I know that would mess up minute registration adjustments, but I need something to keep the stupid thing from moving, even minutely.

I put some scotch tape on just to see what would happen and you can see how it’s shifting and torquing. This isn’t even the big plate (and ignore the messy plate; I was hand-rolling).

Plate movement

7 thoughts on “Plate movement

  • March 12, 2014 at 9:17 am
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    Sorry about the bad link, just copied it from a PPLetterpress post and it got garbled when pasted.
    Here’s a shot of the most basic elements of the system: pieces of lead high base sawn from 24″ lengths, a brad, a pin vise for drilling by hand, and a jig used for one specific job so the holes could be placed relative to the crop marks on the plate.
    I use various methods to locate the holes: measuring from image elements, placing locating circles in the original file so as to drill down through the center, and just going freehand.
    About adhesive mounting: some plates such as Toyobo have more flexible metal backing, very likely to kink when removed from adhesives. Others are stiffer and can be removed, very carefully, without damage. I’ve done a lot of adhesive mounting on forms built up of lead high base strip, and even the stiffest plates are hard to remove from 36 point high base. I generally use 18 or 12 point strip and it is much easier to pull the strips off the plate than the plates off the mass of strips (or any full-size base). I have also used HDF and MDF as base and consider both plate and base sacrificial. One mounting, no reuse for different forms.
    Dali: sheet magnet is the working part of Pat Mags. Just a block of Magnesium with a thin sheet of rubber magnet on top.

  • March 12, 2014 at 7:34 am
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    Dear Jonathan,
    It is true that MDF is not very consistently thick. But: Normally these are only differences from block to block – but normally not within one block.
    MDF reacts very much on moisture, but if you keep it dry it stays good for a long time. I personally never had a block with more than 0.05mm differences in height, to be honest if the block lies flat on the pressbed I never had noticed any measurable differences in height. From about 0.1mm (thats the thickness of a photocopy paper) differences within a block you could start to see a difference in impression. I never had troubles with this.
    But if you switch from one block to the other, that was maybe cut from an other piece – then you could see some differences.
    But you can see these differnces also for example with plexiglas. Within one sheet they’re all the same thickness. But switching to a new plate they differ quite a bit (up to 0.3mm).
    Best wishes.
    Dafi

  • March 11, 2014 at 1:33 pm
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    Thanks, Dafi. I’m running it again today, so we’ll see how it goes. I’ve coated the plate bottom in a light adhesive. I’ve also run scotch tape along the sides of the plate. If those tape pieces start to torque and stretch, I know the plate is moving.

    I have mounted plates on MDF before, although I’ve been told by Paul and others that MDF isn’t as stable or consistently thick as one might believe. I have to shim up the MDF I can get with a couple pieces of chipboard, so that introduces more dynamic that I don’t want to deal with.

    Wish me luck!

  • March 11, 2014 at 1:13 pm
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    I had the problem sometimes before with my magnetic bases and steel backed photopolymer plates. Normally they work perfect for me but in some cases they moved. It eitherway occured when I printed very small plates (not enough magnetic surface) or very big plates with alot of printing surface… I found two solutions working for me:

    1. Using a very very strong doublesided tape they also use in flexoprinting. I use “Lohmann Duplofol 1.0” from a German manufacturer. But I also think that boxcarpress offers something like that. I mainly use this for small plates that would move during printing. I use it right on the magnetic base. I never had any problems with removing “sheet magnet” (?), but our bases look a little different in Europe anyway. Duplofol 1.0 will add 0.1mm in height! Duplofol 2.0 will add 0.2mm! Be aware of this! If you dont cover your full plate, you might have spots with different impressions!

    2. With very big plates, I use an MDF Block, full cover Duplofol and sometimes I even add 3-4 little nails in some non-printing areas! (In Europe, there is a 23mm MDF block. Together with the Duplofol and the steel backed plate I get someting like 23.70mm. Continental European typeheight is 23.56mm (.928″), so I am a little over and have to adjust the packing and the form rollers a little bit…)

    There are two downsides to these techniques:
    Downside A: Registration
    The main advantage from magnetic bases are, that you can move the plates easily and reposition them for registration. When you use doublesided or nails, this advantage is gone… I normally make registration all perfect with just the magnetic base or (on the MDF board) just with a little doublesided. When it’s all perfect, I trace the outline with a sharpie pen. Then add full covering doublesided, place the plate and maybe even the nails on the wood board.

    Downside B: Destroy the plates
    When you peel off the steel backed plates they normally will bend. So basically they are destroyed after use… With the solution with the MDF block there is the question: Do you want to keep and reuse the plate? – so keep it mounted. Do you want to keep and reuse the MDF block? – peel off and discard the plate…

    I guess downside B can be solved by just using plastic plates without steel since they wont bend. But I only have steel backed plates to process in my studio…

    Also a hint for checking if a plate moves during printing: I do the sharpie trick always, also if I have plates that are not likely to move or for example also with linocuts that I mount on wood boards. Just an outline with a pen helps to see if a plate moves or not. The sharpie outline can be removed from the magnetic base after printing with minearal spirits…

    Hope this might help. Good luck and happy printing.

  • March 11, 2014 at 9:13 am
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    I’m definitely going for a heavy impression, so I’m probably overpacked a little as well. I rarely use the patmag, but the plate is too big for my 9×12 standard boxcar base. I’ll try cutting back on the pressure along with some light spray adhesive.

    Regarding packing, what would you suggest is the max not including the actual print sheet? Undercut is .040.

  • March 10, 2014 at 7:17 pm
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    Use a light-duty spray adhesive. Even that will probably remove small amounts of sheet magnet when you lift the plate, but not as much as if you use a permanent spray glue like Super 77. PatMags can be sent back for new magnet covering.
    I use a pin mount system based on pins made from 16 gauge brads driven into 18 point lead high-base the same height as the PatMag, then making mounting holes with a 1/16″ drill in a pin vise. No shift, no adhesive. Any compatible combination of pin and hole making could work; at Arion Press they made holes with a 5 mm eyelet punch and had pins made at a machine shop to match their bunting bases. The pin units are just locked up right against the base.
    Another printer only experienced forward creep of his plates (heavy pressure will do that) and hsi solution was to take scoring rule, grind the face down until it was just aabove mag base height, and then lock it up to the head of the base. Butt the plate against this lip, and the plate won’t creep forward. That won’t help if you are experiencing backward creep, and I’ve seen it in both directions.
    Fritz posted as photo of one such setup before the plate was placed over the pins, and in this particular case the pins are at the tail of the image; sometimes there isn’t enough margin at the head.
    http://farm4.static.flickr.com/3060/2902463422_4d60ea9967_o.jpg

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