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The Context:

I'm trying to print this container with a Voronoi pattern on it. The actual object itself was created using a combination of this online tool and Fusion 360. This was then imported into Chitubox (V1.7.0), rotated by 20°, and auto supports were generated (default medium weight, 60 % density). This was sliced and then exported as a .cbddlp file, stuck on a micro SD (not SDHC) card, and printed from there.

The Setup:

I'm using a 'MonoPrice MP Mini SLA' resin printer, along with Elegoo standard blue resin. The print shown in the pictures below was printed in a warm room (probably ~20 °C), the print bed had been cleaned prior to printing with isopropyl alcohol, and the vat/FEP with warm soapy water; both were left to dry fully.

  • Bottom layer curing time: 120 s
  • Other layer curing time: 10 s
  • Bottom Layer count: 20
  • Transition layer count: 20
  • Light off delay: 1 s

The vat/FEP film was tightened down nicely, the print bed auto-levels before every print.

The Question:

'Simply', why have I got these random holes appearing? I have never had a single issue with the bottom layers not adhering properly, but now I have these holes that are completely surrounded by perfectly acceptable print. Is it something obviously wrong with the model/supports (too complex/flimsy)? Is it slicer related (just not generating print data for those areas)? Settings related (over/under-exposing)? FEP related (too sticky/not tensioned correctly)?

No random gaps on this side (Except for where I broke away a support with a little too much vigour.

No random gaps.

Random gaps here, these extend completely through any supports in the vicinity by the way.

Random gaps.

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  • $\begingroup$ Weight of liquid resin accumulated on plane surfaces or deepenings and/or surface tension sometimes can break away them while part moving up from a resin tank. You could try several things: 1) reduce printing speed, so it can reduce breaking force 2)increase exposure time, so part become harder to break 3) make it a bit more rounded or even sharp vertically to decrease impact area 4)use more rigid material 5) use resin with lesser surface tension. More supports to weak places also could help since it makes them more solid. $\endgroup$ Jan 28 at 16:26
  • $\begingroup$ @StepanNovikov Adding supports wouldn't help since the gaps seem to 'slice' right through them as well. The surface tension idea sounds promising though. When you say "slow down printing speed", are you referring to the speed at which the Z-axis is moved upwards by? $\endgroup$
    – Adzi B
    Jan 28 at 18:08
  • $\begingroup$ Adzi B, yes, it's about Z axis speed while part moving up and in my experience with printing of the Eifel tower (thingiverse.com/thing:22051) failed print more than first platform with SparkMaker without changing geometry with LCD-T resin. They recommend in such cases, LCD-BW, but I didn't have a chance to check it with LCD-BW and I didn't find any specs surface tension for both of them. However, since we have here much less surface area, probably, in such case, decreasing of lifting speed or even simple adding more supports in right places may help. $\endgroup$ Jan 29 at 8:32
  • $\begingroup$ @StepanNovikov Could've been luck of the draw but reducing my Z-axis movement speed (from 100mm/min to 65mm/min) did solve the issue (I did also bump up exposure time from 10s - 12s). I shall experiment with future prints, and if this proves a reliable solution, I'll answer this post with your advice as the solution. Many thanks :) $\endgroup$
    – Adzi B
    Jan 31 at 16:04

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