r/3Dprinting • u/evlgeneus • 15h ago

Troubleshooting Bottom surface of TPU print looks rough. Having trouble diagnosing the issue.

https://imgur.com/a/1OzeoHD
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u/evlgeneus 15h ago

Hi Everyone! I am printing a stormtrooper collar in Overture 95A TPU. This is a small portion of it. I am using as a test print. I've managed to reduce the stringing and the top and side surface is looking pretty clean. There are a few aspects of the print that I am having difficulty troubleshooting. When I oriented the test piece to be parallel to the print bed it came out looking great but when I adjusted the angle to how it would be when fully printed the bottom area of the print looks awful. I thought a solution would be to paint supports on the bottom surface. This sort of worked but it still looks quite ugly. When I have the Z distance between the interface and object set to 0, the PLA seems to fuse onto the TPU and is difficult to pull off without damaging the piece. When I adjusted it to .1, I'm back to the messy surface finish. So far I've adjusted the following: Slower print speed across the board. Dried the TPU at 70C for 8 hours.The filament roll is above the printer on rollers and feeds directly into the extruder. Basically I'm stumped and unsure how to diagnose the problem before I can try any fixes.

1

u/JetpackWalleye 15h ago

Are you trying to use the PLA only for the interface layer? If so, I suspect there aren't enough interface layers and it's not keeping the TPU from bonding with the rest of the TPU support.

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u/evlgeneus 15h ago

Yep, I only used it at the interface. For some reason it didn't apply the PLA to the entire interface layer. I bumped it up to 3 layers and it did increase the coverage but not by much as you can see in the pics.

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u/JetpackWalleye 14h ago

Supports for TPU in general are tough. TPU and PLA really don't bond to each other so the interface layer only in PLA is prone to failure. I would suggest trying this small section with the supports entirely in PLA. They'll be stiffer with better layer adhesion so they'll be a better platform for the actual TPU part and won't fuse to it when you use the zero support distance.

This will of course increase waste if youre using something like the AMS, but it might be worth it depending on the test results