Fun with Elastic


#1

I’ve been having fun with Elastic Resin which is pretty amazing stuff. I printed this for a customer and it came out excellent. Watching Elastic print is fascinating in itself.

What was a little puzzling to me was about orientation as far as Preform’s built-in checks. At first, I wanted to orient it so that the opening was hanging down to form a drain for the resin but Preform complained about the cupping whereas with the above it does not (complain). I suppose from Preform’s perspective the bottom of the vessel stays open until the last N layers. What factors does Preform use in determining if resin will pool in an enclosed space?


#2

Glad to hear that print worked well for you! Did you need to remove internal supports after printing, or did you print without them, or did you leave them in after printing?

I don’t know exactly what’s going on in terms of Preform’s algorithms - not my department, but basically anything* that’s concave facing away from the build platform is going to be treated as a cup. Or, anything* that is like a closed dome getting pushed down into the liquid resin during the print. (*unless very small cups are skipped over) Speculating about the algorithm, maybe if there’s more than a certain number of layers with interior edges that are above a solid area, or maybe a recursive search through layers with interior edges to see if there’s a path through earlier layers to open space?


#3

I printed with internal supports (could not think of a way to avoid) and left the supports in. Funny story that. I actually printing this twice. The first time I thought I’d be clever and crush the supports after cure by squeezing the model (gently) and then remove the pieces with tweezers out via the spout. Was going good until I nicked the inside of the model with the tweezers. The model literally exploded from the inside out. I suppose that by definition, there’s a fair amount of elastic pressure and any small nick inside (where in this case there’s the least amount of curing going on) causes a dramatic release.

hmm… exploding whoopee cushions anyone?


#4

You’d get a better print result by flipping the model so that it starts from one of the bottom corners


#5

True enough and normally I would to reduce the surface area that has to peel. Doing so with Elastic, inflated the build time dramatically however. You also want to avoid overly long support structures. The part came out perfect BTW. Elastic will be in my material repertoire for sure.


#6

Ok well I take back what I said about part being perfect. It’s about 1% too big. What the dimensional accuracy of elastic resin parts?


#7

https://support.formlabs.com/s/article/Using-Elastic-Resin?language=en_US

The dimensional accuracy is tricky for Elastic - we do our best, but it’s a compliant material, and it’s compliant during the print process, and it swells as it absorbs IPA, so the final dimensions can be sensitive not only to the wash and cure process, but also the surface area-to-volume ratios of different areas of your print! If you have to wash relatively thin parts for a relatively long time to get them clean, they could become significantly distorted. In that case, they might return towards normal if you allow the absorbed IPA to evaporate before post-curing them.

Perfect dimensional accuracy may be quite difficult to achieve, but I think your best bet would be to keep the orientation and supports and wash and cure times the same, and see if scaling it down 1% fixes this part for you.


#8

I wonder if this is a good case for using other wash liquids like Yellow Magic? Would Elastic absorb water as readily as it does IPA?