Keeping paper on the press bed!

Die cut after printing. Thats all I can think of.

There are a couple things you might try:

1. Tape down several pieces of the coaster stock surrounding the coaster, creating a nest to hold the coaster in place, maybe setting them a bit tight to the coaster, so there would be a little bit of resistance to removal. They won’t be easy to feed, but may pull from the form to get the job done.

2. Use some tack reducer in the ink to make it a bit less sticky. A light varnish or a bit of Vaseline or kerosene (just a drop or two) will reduce the tack it you don’t have any purpose-made tack reducer. This will allow for better release from the form. Mix it in well with the ink before inking the disk.

Daniel is really correct that die cutting after printing would be the best way to handle a bleed off all edges, but I assume you might not be ready to do that kind of work and need a work-around for a job that needs to be printed.

John Henry

A bit of post-it tape on the tympan under the coaster…?

A chute under the bed to deliver the dropping pieces…?

Regarding terminology, you want to keep the sheet on the platen, not the press bed. The form sits on the press bed, and the sheet sticking to the form is your problem.
You can’t print a full-bleed image and still feed to gauge pins. Even butting the image to the guide edge is an unreasonable expectation. You absolutely need margin at the guide edges so the form clears the gauge pins, but especially the tongues of the gauge pins must clear the form elements so that they can strip the sheet from the form. With heavy solids tongues may not be enough so that’s where the grippers and fingers and friskets come on, or tack reducer as already suggested.
Attempting the impossible on a motorized handfed press is asking for not just trouble, or a spoiled job, but even injury.

I sometimes use bits of double stick tape on the tympan for this. I usually blot it several times with a t-shirt to make sure it’s not too sticky.

Print 1st, die cut 2nd is the proper process. Also - throw some Smoothlith into you ink mix. It will give better color results and will definitely reduce tack.

OK this is pretty far out there and certainly outside any definition of tradition but… On a screen printing press that I worked with the platen of the press contained a vacuum system to hold the substrate still during the imprinting, and then was timed to release suction to load the next item.
This might not be that difficult to set up on a letterpress. You might need have a thin thread under the tympan to let air move, tape all around the tympan to make air tight, small pinholes in the area of the coaster to get suction there, and some kind of switch set to release pressure after the platen leaves the form.
Another issue comes to mind though. If this worked, how would you pick up the coaster with wet ink on it and no margin without smearing the ink?
Bruce

Diver press: you could give this product a try.

http://www.silkscreeningsupplies.com/product/CCProBondP

It has worked for me for many similar applications to what you are describing. I also mount sheets to ‘carriers’ with it to print deckle edged paper without ever having to handle it or slit it and then tear it down during the printing process.

Note: I wouldn’t suggest coating the entire tympan, or even the whole area behind your coaster.
About 30% coverage is all that you should need. In theory it should be tackier than the ink, especially if you add a little tack reducer to your ink too (I’d recommend this).
I’d suggest a drop or two right behind where your coaster will land on the tympan, about centered, and to rub it in a twist with a rag to thin it out. Your tympan will actually deflect just slightly, FYI, so you’ll want to make sure it is good and tight.
Before you get going, hit the adhesive with a hairdryer, to warm it up and engage the tack qualities and also flash off any moisture content. It is advisable because heat also improves the adhesive’s tack qualities.

The first couple of pieces might be a bit sticky, so run slow at first- in fact, one at a time*- but as it picks up paper fibers it loses it’s tenacious tack and will become managable. You could try the Tshirt trick mentioned above, that would probably do the same thing.
You’ll also need something like a credit card to gently pry the coasters off most likely, and probably will run slow. I really sincerely hope you’re using a manual press or a press with a brake on it. The job will be slow, slow going- but this is one way to skin the cat.

*Edit: Where I said one at a time? Yeah, I’ve fed round stock coasters 2 at a time before hahaha. Not….! Don’t know what I was thinking.

Does anyone remember gripper fingers

Haven press,
The product you are describing is another version of carpet tile “tackifier” it does exactly the same thing ,stays tacky and is never really dry , i use the carpet version for such tricks although your link is aless costly product , thanks !!

James, I’m guessing you didn’t get to the part where the OP was trying to print full bleed coasters.
Uh, read the post bud- the idea of using a gripper finger on a full bleed, round substrate print is not exactly beneficial.

Of course, if there were any margin whatsoever, I’d be suggesting some rubber bands and gripper fingers way out to the sides, but since it’s full bleed- tacky tympan (should I try to copyright that?) it is.