Multiple problems with Clear Resin V2

I just bought a brand new Resin Tank with Clear Resin V2. I printed the Butterfly badge that the Preform software defaults to, and it printed well, no problem.
For my second attempt, I tried to print this cat:

First I printed it upside down, top of body/head attached to support structures. I got most of the print attached to the resin tank. Cleaned tank, no scratches, rotated cat on it side. This time, the cat printed completely, except it was missing one leg! AARGHH! So Close!
Then I took a close look at my tank and I found a mat of resin covering the entire bottom of the tank. It was about 3 mm thick, jelly-like in consistency. (Anyone seen that?)I peeled it off and tried again.
For my third attempt, I increased the support structures to maximum, kept the cat on its side as in attempt 2. This morning, I woke up to find the ENTIRE print firmly glued to the bottom of the resin tank! Three whole prints and I am now out $58 + shipping for a resin tank!

Questions:

  1. Any ideas what I am doing wrong? I see the posts to increase/decrease the platform height. But that is a crapshoot isn’t it? There is no way to calibrate HOW MUCH adjustment is needed. The first print came out fine, so why should I believe the platform height is wrong?

  2. Is it worth scraping off the print to save the resin tank? Or will it be hopelessly scratched at that point?

Hi Roshan.
You can put an empty tank in the printer and start a print. When the platform gets in place for layer #1, you can lift the lid and inspect the gap. Then use the PreForm fine tuning tool to adjust. It’s in MM.
And the resin on the bottom of the tank should lift off without any damage.
But if the “resin mat” is beyond the model very far, you might be having mirror or laser problems.

Thanks Josh, I will try adjusting as you suggest. I will have to wait to order another resin tank, though.

If you have a disposable cup you could use the FormLabs scraper to squeegee the tank you have empty and just use that one. It would save time.

There is no way to calibrate HOW MUCH adjustment is needed. The first
print came out fine, so why should I believe the platform height is
wrong?

You don’t need to be exact with the platform height adjustments, I found my first prints weren’t sticking so I knocked the platform lower by a few points and it was fine (try 0.2mm to begin with), as long as you don’t go to far the change is so small (just a couple of layers less) it shouldn’t do any harm, the first few layers will just be slightly thinner.

Your first parts may have come out ok just due to luck, if it’s only slightly too high (or not perfectly level) then there may only just be enough purchase on the platform to hold it, hence becoming unstuck at random.

Is it worth scraping off the print to save the resin tank? Or will it be hopelessly scratched at that point?

I’ve scraped a lot of failed prints off the resin tank with the formlabs scraper and never scratched it, as long as you keep the scraper flat so the whole of the edge (rather than a corner) is on the PDMS layer it seems to have no problem removing parts without scratching. Sometimes you need to use more force than you’d think, but the tanks have for the most part been fine.

One thing is try to push the stuck resin rather than lift it off, I did have a stuck print rip a part of the PDMS layer off when I tried to lever it off, it might have been fatally stuck on it anyway but I’ve always been more careful to push horizontally until the stick part is definitely free.