Anyone out there have any insight on polymer plates moving around while printing?
I have been using deep relief polymer plates from boxcar. the adhesive feels more than necessary for the boxcar base. I have spent hours upon hours calibrating the platen and it seems to be striking evenly and flat.
i can typically print 30 or 40 before the press starts to move the polymer north. once it starts to move, it will typically move 1/2” up in 1-2 print passes.
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This is not as common on a platen press as on a cylinder press, but can occur. One simple fix is to clean the base very well with isopropyl alcohol or a stronger solvent which dries without an oily film. It could be the adhesive is not getting a good bond to the base material.
If that doesn’t work, you can tape the edges of the plate to the base in areas outside the printing area. this gives some extra hold to the adhesive and may be enough to eliminate the plate creep during printing.
What a confounding problem!
Question for clarification: When you say ‘up’- do you mean towards the ‘top’ of the chase/base, in other words the plate is visibly moving/migrating towards the ink disk? This would point to a few different things.
Acetone could do the trick as far as degreasing the base- I just have to ask for the sake of elimination, is your base seated in the chase properly/locked in good and flat?
the base is locked in flat and properly, i have actually reset the base multiple times and even purchased a new chase thinking that maybe the chase was the issue. as far as the surface being clean, well that is not the issue. i have reset it multiple times and cleaned and cleaned. the polymer is actually quite difficult to remove ever after being slowly shoved towards the top of chase/base. towards the ink disk.
if i center the boxcar base inside the chase, and then if i center the polymer on the boxcar base (so that it is dead center) it prints fine and does not move however it doesnt ink properly because the rollers are continually hitting the light spot, also dead centered, on the ink disk.
currently, if i hand ink the plate and print a single sheet, everything appears to be calibrated and running smooth….for some reason it just moves the polymer around.
Perhaps if you cannot find the cause and have to use what you have. Maybe low-slugging a bumper to be, the height of the base material, placed on the side of the direction it is traveling will help. Knowing this in advance, one could plan on the base material reaching out that far, to that side of the block or base you are mounting it on. I would be curious how low the roller kiss is. Sometimes you have to raise them. Standard is 1/8 inch for lead but what works works. Image crispness may improve too. Also are the rollers pretty hard? Amount of impression is perhaps a factor as is ink tack. Good luck.
Do you have a ink roller gauge? The strip should not be any wider than 1/8 inch. If it is wider, adjust rails to lift rollers higher so that the pressure on the polymer is decreased. If rails cannot be adjusted, add two strips of tape over the rails and try it.
All the above comments are relevant and useful.
“In my day” when this problem arrived, we followed procedure, some of which is mentioned above.
1 Make sure the plate is properly adhered to the base, all over. [more to come in a minute]
2 Is the plate and base exactly type high, [.918”]
3 Is there excessive overlay makeready pushing hard against the plate for the often too “deep impression”. [My terminology, see my comments on this issue in past posts.]
4 Yes, check the roller coverage and setting, and make sure they are revolving in synchronisation with the roller tracks down the side. Need to oil the hooks over the roller spindles often! The rollers must never under any circumstances print to the bottom of the plate, causing inking marks.
Now the tradesman speaks:
5 If you are using a flexible synthetic substance for the plates, allow enough non-printing area, head and tail of the plate, to allow for scoring [not creasing] on the underside of the plate to be bent over the synthetic base, preferably almost to the full depth of the base, but being a mm or two short of the base sides height. This will act as an anchoring system. The scores must be parallel, or you’ll need to “swing” the plate to correct! Care when scoring so as not to cut too deep and thus allow for tearing of the plate under impression.
Needless to say you’ll have the whole underside area of the plate double sided taped to the base as well.
Lock up the unit with the overhang, head and tail, into the chaise and hard up agains the furniture, and print for Profit.
6 If you are using rigid based photopolymer plates, and want to use them for repeat work, consider mounting them on Cornerstone/honey comb bases with associated quoins. OR, mounting them on appropriate height wooden ply wood. When using wooden bases you will need to forget tape and instead counter-sink small panel pin holes through the plate and tap in the finest of wood nails/panel pins, any safe number, making sure that they are below the cleaned wash-out area on the plate. Using wood bases obviates the need to lift and ruin the plate.
7 When one is applying excessive deep impression, it stands to reason, that unless you adjust the parallel of the paper platen there will be uneven pressure, causing the plate to shift in its resistance.
8 I draw your attention to my website, www.willamer.com.au.
which is about to undergo a major review as I will be retiring after my 70th birthday in 2018.
It contains nothing technically useful, I sell all my experiences to my students like any school. I hasten to add there are no “tricks of the trade”, just experience.
Kind regards, William Amer
thanks so much for all the advice.
the rollers i have are basically new (low mileage) and nice & soft.
everything is running type high.
i have a roller gauge and currently everything is hitting at 1/16 of ink strip on the gauge now. i removed the layers of old masking tape and applied uhmv tape and it seems to be much better now….although it does seem like a bit more ink might be nice. ill have to play with it more to know for sure.
after all the advice and screwing around i think the issue is me setting the polymers with too little “heads and tails” on the base.
i was initially told to force my image to upper right hand corner (towards the ink disk and upper feed table) but logically, it seems wiser to have the image a bit more centered in the chase and on the plate…(does that sound correct?)
Come to my school in NSW Australia, it’ll be cheaper in the long run!!!
Check the roller trucks for this kind of wear, which in conjunction with stuck bearings, might allow free movement of the rollers in one direction but not in the other. If the rollers are not moving freely as they move upwards that could be pulling your plates up.
Delrin truck wear.jpg
The C&P is not a parallel impression press. The platen and print surface converge at an angle and only reach parallel at the moment of printing. If you are printing with heavy impression this means that the plate is plunging into the sheet at an angle. If your plates are cut small, they could easily migrate upward on the base.
Quite true about the CP not being a press where the paper platen approaches the type platen in a parallel movement, but at the moment of impression of the CP, the skilled printer understands that the CP paper platen must be in parallel, particularly on any image larger that a pin prick.
William Amer, Rockley. NSW