Swelling in the center of a print

My prints come out swollen every few prints.

I have been having trouble with a print and so Iv’e bought a new tray and more resin. My first print was a failure but I am sure its because I put the parts to close together. I moved them apart and viola! The second print was perfect. Then I added more parts to the print and the center was swollen like the first print was. Does anyone know how the parts get swollen before the IPA bath? Is my mirror need cleaning? my laser bad? Its weird that my second print was perfect, I wish every print was like that.

PS. I print the same parts over and over. I don’t really print anything else.

This is the first print

this is the second print. Notice the swollen ones in the center and some around that.

Quote_3023.stl (50.5 KB)

This is the file as it should be, Nice and crisp.

The good news is I don’t think it’s your printer. What I think is happening is there is poor resin flow near the center. I know that seems a bit silly to blame, but I think it makes sense… The resin near any model’s edges gets mildly exposed to light from printing, and needs to be sloshed around after each layer, but that is not happening for you because of poor resin flow. So it sticks around and alters the exposure needed to cure resin in that area of the tank. We have seen something similar with faulty lasers, but that would not affect just one area of your tank. And you did just have a perfect print.
I would recommend standing your models upright to allow better resin flow. And if needed space them further apart too.

Thank you! I will try that.

Another (odd) idea - try staggering them.
Instead of a rectangular matrix, use a diamond-like arrangement or random stagger.

I have seen a huge difference in quality now that I’ve changed the orientation to vertical. Also i have spaced them out as far as possible while having the base touching on every part. Perfect prints every time! Thank you for you all your help

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