I’ve had this happen a few times now, usually at 50 micron Z resolution and black resin:
The supports are missing, but it’s not a matter of them going missing mid-print - they never built off the base in the first place. There’s a very slight bump on the base where they should’ve grown off of, but that’s it.
(As you can see, it’s not a failed print, as the “missing” supports managed to “recover” mid-air near the end from the branches of the nearby supports and the object itself printed fine as there was plenty of redundancy.)
So here’s the thing - i don’t get what might the cause be. I thought it’s that the base isn’t thick enough, but i’ve printed a few prints immediately before this one, with a 1mm base and those were fine.
I used to occasionally see that if my build platform was over compressed, but that doesn’t appear to be the case here. Have you tried printing the part in a different location or rotated 90 deg? It would be interesting to see if the location affects it. Also, did you try reprinting the same job? It could just be a fluke.
Haven’t tried 90 degrees, but tried a different location. I also tried a different print in the same location. I can’t successfully and consistently replicate it nor find any correlation with anything, except, possibly, layer height and base thickness.
What i did notice is, that when it happens, the height where the supports begin coincides with the place where i’m seeing layer splitting in the base itself - in the release tabs. I.e. when it happens, the tabs became malformed too, crack very easily and are sometimes even completely deformed and mushy.
(Edit: you can see it in the photos above too - look for the tabs, they’re deformed enough to be almost hard to even recognize.)
(Edit2: it might be that my platform is tweaked too low too, i’ve had to lower it by 0.3-0.4mm in order to get prints at 50um to stick to the platform when using black resin.)
