Grey Test Print - Big Mystery Hole

I tried a part in Grey Resin today. New tray, new resin, 100 micron layers on a simple part (box facing down). It came out with a gnarly hole in it with uncured  material hanging on around the edge. I checked the bottom of the tank, assuming there would be a nicely cooked slab of resin there, but it was clean. I swept a silicone spatula blade through the tank a few times expecting to find big globs of half-cured resin and found nothing. Mirror looked clean although the light wasn’t perfect. I checked the slices through that area of the part and they look good. Preform grumbled about the .stl file but seemed to heal it up OK.

I’m running the opposite half of the box tonight. I dropped down to 50 microns , tilted the part at a steeper angle, and rotated teh long axes of the part in line  with the tilt direction (setings that worked with the clear resin). I guess I’ll see how it goes.

Possibilities that cross my mind:  Dirty mirror.  Bad batch of resin. Weak laser that can’t cure all the way through 100 microns of grey. Bad .stl file. Bad silicone layer in tank (someone spilled sunscreen in the batch of silicone, I dunno). Has anyone else seen this?

Did you try printing it twice?  Be interesting to see if it happens again in the same spot or not.

I printed a small bust (snagged off of Thingiverse, IIRC) and the head was basically missing.  I tried two more times with exactly the same failure-- looks fine in the sliced, but I’m kinda convinced it’s an error in the slices going to the printer because all failures look identical even when scaled up or down (seems unlikely the model would fail to print exactly and identically wrong all those times.  Rotating the object however results in a full print.

I damaged my mirror (permanently fogged the center, basically) and that results in something of a ‘melted’ look in the affected area.  If there’s an opaque obstruction on the mirror you get a hole/line cleaved through all slices of the model.

My ‘small’ mirror (the first one the laser hits under the Z-axis leadscrew) had a big fingerprint on it when my machine arrive, so you might check that too.

I rotated the part 90 degrees on the platform, tilted it up 30 degrees instead of 10 and switched to 50 micron slicing from 100 and it built fine. It had a few bits of half-cured resin stuck to it, but they cleaned up just fine. The steeper tilt angle caused the small circular bosses to become more elliptical, but I’d left a .010 " gap from Plastic to PCB on most of them, and the board dropped in just fine. That is pretty cool!

The plan is to try a 50 micron build directly on the print bed (0 degree tilt) to see how that goes.

Sorry to hear about the damaged main mirror. Hopefully it won’t set you back too much to replace it. Thanks for the tip on the first mirror. I’ll have to get a light in there to see how things look. I’m surprised a unit could pass QC in that state.

Happy Printing!

Here are a few pictures of the parts. I’m running these as check prints for a client, so I’m trying not to give away anything that might be revealing about the product. In general, I would give the printer a poor grade at 100 microns. The rounded corners came out surprisingly bad. At 50 micron resolution, things improve. The steps almost disappear and the corners came out well. Still had a few small gaps (air bubbles?). The pictures show the 30 degree tilt affects the roundness of the bosses.

Sorry about the color balance. I guess it’s a bad camera day.

Hi Andy,

You have air bubbles not escaping. Please see my post  “Hi Folks, successful prints of small parts”.

good journeys,