Underside of prints messy?

Hi everybody, I have a simple question… I noticed on my prints that the part that’s facing to the platform - so has all the supports connecting to it - is usually a lot more messy and failed then the upper part that’s facing towards the resin tank - which is usually crisp and clean. Is this something that’s happening to everyone? Or is it just my prints? Can I prevent this happening or maybe increase the quality? I’m already pretty satisfied with these models but it would be great if I could eliminate this issue.

Some examples:

As you can see the print is more or less perfect, but the underside has these little holes and wave effect - it should be a smooth cylinder

Bigger wave more visible from an other angle:

Upper side is perfect, crisp and you can see the build lines. The other side is usually kind of melted together.

Any ideas? Maybe it has to do something with the peel mechanism? Resin getting stuck on the surface and curing? that curved line on it awfully looks like flowing or dripping resin…



I noticed this also, Form 1+.
By all parts the side to the platform the contours are not so sharp/exactly
than the other side to the tank.

No success with different positions.


I too was having this issue with the grey resin. Sometimes worse than others. Often it would be really bad near the support points. I just started using the version 2 grey resin, and I have to say it is fantastic. Like night and day. I don’t see that issue at all anymore.

I’ve also started to approach post processing different too, and the results are very encouraging.
Initially, I would try to cut off the supports while it was still wet with resin, thinking that it was as ‘green’ as it was going to be, the supports would come off easier, and I would not waste IPA cleaning the supports. Results were not that good. Then I tried just soaking the whole thing with supports first, squirting in the spaces around the supports with the squirter. Now, I agitate in the ‘dirtier’ IPA for about 30 seconds, squirt around the nooks and crannies, then blow it off with an air hose, The air really helps clean it off. I repeat that process with the cleaner IPA, and then let it sit. The parts are coming out amazing now. And I really cannot get over how accurate the parts are. It’s mind blowing.

I am currently having this same issue with the white resin. Any area facing the platform turns out really messy. In some places the gauges are .5mm deep. I was wondering if anyone figured out the issue?

These two were printed at 90 degree different angles.

To my knowledge, there are two causes for this:

  • laser overshoot - the light doesn’t just conveniently stop propagating beyond the layer currently being printed, it continues through the next layer - the amount of “bleedthrough” will vary from resin to resin depending on the amount and kind of pigment

  • peel mechanics - if an edge of a layer isn’t attached to the previous layer, the peel will deform it slightly; that’s not a problem on the top (tank) facing side of the object, because the contact with the PDMS will flatten it when the next layer prints, but the bottom (platform) facing side will remain slightly deformed

Net result of both is that the bottom sides of the prints will always have worse surface quality than the top, especially if the bottom is at an oblique angle. I don’t think this is avoidable, but i might be wrong.

Hello! did anyone find a fix for this issue, I can’t seem to find much else on this issue except this thread. :confused:

Support side is always the least quality on sla printing. With a fresh tank and warm resin along with steep angles will help but as the tank wears and if prints have low angles on the support side the resin tends to collect. Warm resin will lower the viscosity which really helps with the crispness.
For myself I have been having the best luck with the clear resin and seems to be good for general purpose. I haven’t had any problems with details and the steps on the layers are almost impossible to detect on 25µ-50µ

There’s no way to avoid the bleeding of the laser through the resin which cures extra resin on the underside of prints. For the Form1/1+ it’s important to make sure that your mirrors are clean. In all printers, make sure you have enough support to keep the print stable while printing, but also consider the orientation because good orientation can allow you to use the least number of supports which will give a cleaner print.

1 Like