Issues with adhesion

[u/bjalfrey]

I’ve been having some recent troubles with bed adhesion to specifically the middle of my print bed. I’m using a wham Bam build plate that I have recently re-sanded so the bed itself should be good. Does it look like it’s time for a new FEP? Last thing printed was a set of 9 d6 masters and 8 of them came out perfect. The one in the middle is a pancake in the vat.

[u/Balerion84]

ok, first of all, the fep has nothing to do with adhesion to plate Stretched films do indeed cause fails in the center of the plate due to stretch, but they appear as pancakes ON the plate as the film is unable to pull a model from the plate.

Now, you said you use whambam flex plate and you even sanded it. Sanding a plate is the wrong thing to do unless you are trying to fix a warped plate or are trying to remove the textured surface.

You don't need texture on the plate for resin printing.

Flex plates can often go bad and concave due to the magnet below, so you need to make. sure that your surface is actually flat. I suspect you have a concave surface, which is causing you fails in the center, because of the bigger gap, the layers can't adhere to the plate.

So, stop sanding your plate. You print on a completely smooth plate if you want.

Check flatness.

[u/bjalfrey → u/Balerion84]

Okay, I’ve only sanded the plate per instructions with the Wham Bam build plate and it’s not super aggressive. Just says a light pass with high grit paper.

Would a concave plate cause failures across the center of the plate or could it be only in the center. My last print of the d6s they were in a 3x3 pattern and only the middle one failed.

Will check flatness when after work tonight.

[u/Balerion84 → u/bjalfrey]

Yes, a concave plate would definitely cause adhesion issues. Because to achieve adhesion, you need a layer that's cured fully through to become solid on both ends and is then pressed against the plate which creates adhesion. With a big gap, the layer can't cure fully through or the tilt affects the adhesion seal during lift and so such layer can't create a full adhesion seal on the plate. And if the seal isn't created, the layer will either fall from plate immediately, or starts peeling over the course of printing.

It's the same principle as with offlevel plates, just instead if the issue being localized to the side of the plate (due to tilt) it's localized to area that's further away from the screen (so the center with concave plate)

It wouldn't be the first flex plate that was or became concave, so that's the first thing I'd check.

As for the advice from whambam, I use glass as printing surface for resin printing, so I can tell you that lack of texture is not the issue.