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I've recently purchased an Elegoo Mars Pro 3D printer.

I've read about that percentage of resin shapes going smaller and I understand that. But are slicers (or software which help with the joints) already taking that into consideration? Resines vary, and with them that percentage varies too, so is the software applying that error margin or am I the one responsible on this?

Also, is that shrink percentage constant? Like everytime I print 5 mm it will shrink to 4.7 mm, or it depends on how is curated and other random values so it could be one 4.6 mm and the next printed shape to be 4.8 mm?

It depends on the curation process, or the printing process? If I print 2 separated parts alltogether in one single print session, both will have the same shrinkage, or it will depend on the curation process of each of them individually?

If it's not constant...

How can I ensure that all parts printed separately will fit together when joined later on and it won't create a sort of Frankenstein figure where nothing fits? Is there any process to reduce that shrinking to a minimum, even if it takes longer for each shape to cure?

I'm not referring to "clipping parts", but edges and so. If I join two separate parts together, and one of them is smaller than the other because of the shrink of the resin, then the edges won't fit and won't be a clean join.

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  • $\begingroup$ This is less printer but much more resin dependant. You might experience different results on the same printer with different types of resin! $\endgroup$ – Trish Aug 19 at 18:35
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Generally, this behavior isn't well reearched as of this moment, and it would be dependant on your specific resin. While I can't tell you if your resin is affected by shrink or even uneven shrink, I can give you the method of how to investigate:

  • Download or design a cube with a well-known dimension. I'd suggest a cube of 20 mm side length. It's best to indent the orientation onto the surfaces. One such model would be thing 3090144, which has a version that is hollow and has a hole to let out resin, but there are others.
  • Align the X, Y and Z with the letter into the positive side of the axis in your slicer.
  • Print.
  • After Printing, clean and cure
  • Only after curing, measure the X and Y and Z dimensions with calipers.
  • Calculate shrinkage: Measurement divided by 20 gets you the shrinkage or expansion, multiply by 100 for percent.
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  • $\begingroup$ Thank you for your answer! I guess the only way to find an answer to some of my questions is just wasting resin and testing for it (and for every kind of resin I use). I will leave the question open, however, to see if someone can answer with ways to reduce the shrinkage amount. Thank you! $\endgroup$ – Unapedra Aug 20 at 6:49
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    $\begingroup$ @Unapedra true, you will need to sacrifice some resin and print time, but until someone does a scientific study on the matter, this is the best I can offer a the moment. $\endgroup$ – Trish Aug 20 at 8:55

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