Flexible Shapes using Flexible80A - Thin Walled Dust Boot

I’ve been having a go trying to print something my company would usually have molded in just a few standard sizes, a dust boot. This one is for a particularly low volume project and has several deviations from our standard design, an excellent value proposition for 3D printing!

I’m attempting this on a Form 3 using Flexible80A, no experience with that particular material, though I had done several functional parts in the past using the original Flexible. This is absolutely the first part though where dynamic flexibility has been a design goal (previous parts were maybe gaskets/seals, just had to stretch over something and stay there). As you can maybe imagine from the below picture, this thing is intended to compress and extend. To that end, the wall thickness in the accordion section is only 0.8mm! The flexibility seems to have led to some print failures…


This one is actually my most recent attempt, and failed in what I’m guessing is a similar (though less dramatic) mode to my first failures. At first, I was orienting the part vertically, wide end near the build plate.
My post mortem on that first print: I had a couple ridges of material sticking up from the tank, and about 1/2 the part hanging from the build plate, there was clear evidence of tearing.
My assumptions: Despite the many (thin and rubbery) supports that had been placed between ridges, the whole part extended and then compressed substantially during the z-stage motion between layers (I did see this before letting the print finish overnight). At around 3/4 of the way through the print, this eventually caused too much error (assumption) and I ended up glued to the bottom of the tank. Then as either the z-stage kept progressing upwards, or maybe when it went to return home at the end of the print, tore the boot in half. (tear could also be fatigue related, but at only ~1000 cycles I’m hoping not for my sake XD )

This most recent attempt (pictured above), suffered a similar fate, with a small section of the last surface failing, and sticking/silhouetting to the bottom of the tank. In the horizontal orientation, there’s much less compression/extension going on, but still some due to how thin the walls already are. I plan to try again this evening with more internal supports (also stepping down touch points from 0.5 → 0.4mm, since the walls are quite easy to tear). One downside of having to go horizontal is the cure is ineffective on the underside, unless supports are removed first; a difficult proposition in the green state with this material/part.

Drat. Print with more supports has basically the same failure as last time, the same area failed to print/stuck/silhouetted to the bottom of the tank. Does anyone know if the beta print settings might help with this? I’m also printing on 0.05, would coarser layers help?

Interesting to see that it only fails at that particular section. Is there something different about that area in terms of wall thickness or diameter than elsewhere?

Usually failures in flexibles are caused by too much deflection during peel/motion as you’ve noticed. This is either caused by parts that are orientated too tall, or parts with too thin walls.

A 0.8mm thick wall is bound to deflect lots. I’d increase the wall thickness if you can at all.

Otherwise printing at 100um might make your layers stronger and more resistant to tearing if you have any weird thin layers that are spanning across supports.

I would personally try slicing this with zero internal supports but with significant manual supports placed on the outside. You’d have to see how preform does or doesn’t complain, bit removing internal supports like this will be a huge pain, especially if you are doing so after cure. Another thing to try is to see whether orienting this by 15-25 degrees might result in better layer formation and less deflection…but I suspect probably not and I assume you’ve already tried a couple of different orientations.

In terms of post processing, I always use 0.4mm touch points at 0.8 density, and manually remove clusters that might bond or merge together. Also always remove supports before cure (very carefully), because it’s 100% easier when in the green state.

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Another suggestion if nothing works, is to design in some custom supports on your CAD model that increase stiffness in your part, but then can be snipped away fairly easily. Not ideal I know, but if you HAVE to have internal supports this might actually end up being better/easier than trying to remove a whole bunch of preform supports.

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Took several of your suggestions, and got a good part! Was able to print vertically using a from CAD support structure on the inside, which conveniently also comes out in one piece! Unfortunately I was too excited about that piece, and removed/inserted it several times to show co-workers, tore the boot when the IPA dried. Oops.

But yeah, with that custom support, I was able to turn off internal supports which made post WAY easier. The deflection was no longer noticeable, even towards the end of the print. I also turned touch points all the way down to 0.3 after my first layer (also went to 100um layers), came off beautifully in the green state; decided I liked also doing the removal while still wet from the IPA, helped prevent tearing the boot with my fingers.

One note with the internal support, I think I will have to reinsert it at least once, or leave it in, for the cure on the next part. The boot shriveled up once it was removed, hopefully curing with it in place will “lock” the boot in that state. Shouldn’t ultimately be an issue wither way, but not something I saw before with the preform supports.

Once I get the next one done (and don’t tear it) I’ll throw a picture up here. Will also try to post it as assembled once I get the other parts in about a month.

Awesome! Really happy to hear I could help. I’ve had my fair share of torn and failed Elastic/Flexible prints so happy to share the knowledge.

Yes - removing supports when the part is wet - either with IPA or with water is definitely the way to go.

Removing flexible supports after cure is significantly harder then before, so hopefully that will work OK for you. You could also try the following after green state support removal.

  • Curing without heat, but at 2-3X longer. SLA resins have low HDTs and thin walled parts tend to warp during the standard post cure
  • Cure under water. The water will prevent the final part from feeling tacky, but might also help support your part and prevent it from collapsing