this post was submitted on 30 Mar 2025
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I'm trying to print this part out of Filament-PM TPE32 on a Prusa Mk4 with a textured sheet and I'm not having much luck.

The part is a bellows with a 100%-infill plate at the top and at the bottom. Despite leaving a giant brim inside and out, the whole thing has minimal adhesion to the bed and invariably comes off when the print reaches the top-heavy section of the part.

It's maybe the 10th print I'm attempting, slowly trying to dial in the parameters. I had to crank up the bed temperature to 47 degrees for the first layer to achieve any kind of adhesion, which is odd. I have other TPU/TPE filaments that stick better (but they're too hard for my purpose).

I could achieve slightly better adhesion by cranking up the nozzle temperature above 235C, but then it start stringing so bad it leaves raised obstacles almost immediately on the first layer while building the brim, and then the head slams into the obstacles and dislodges the brim at the second layer. The only way to get a good brim (and a good part) is to lower the nozzle temperature to 223C.

Clearly the problem is that the Prusa Mk4 is a bed slinger: it shakes the part loose. We have a Prusa XL on the way that should take care of the problem, but it's coming in 3 weeks and I need the part now.

Before I slather the bed sheet generously with glue, any advise to make this print succeed on the little Mk4 without making a gooey mess with the glue?

Here's the PrusaSlicer project file if you're interested.

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[–] [email protected] 2 points 3 days ago* (last edited 3 days ago)

What have you done to clean the bed?

I cleaned it with water and dish soap. There's nothing like it for adhesion. Even IPA doesn't quite get the same results.

Has the TPU been dried?

I left it in the dryer at 55C for 3 days. The internal hygrometer says 13%, I tried drying it hotter than that, but then it seems to have trouble travelling through the silicone tube - like friction or something.

What’s the max speed you’re printing at?

Whatever the default is for the Prusa-supplied preset for this very filament brand and make. I just lowered the nozzle temperature to prevent stringing and material "balling up" on the surface, and I raised the bed temperature to increase adhesion a bit.

In addition to a brim, have you tried adding supports?

There is a ton of support for that part: it's organic support and it's growing inside and outside the part without ever touching the part itself. The reason being, it's basically a thin bellows that's two layers thick, so I don't want anything supporting the bellows, or any support growing from the bellows, because it's super-fragile and it won't survive removing the support. That's one of the reasons why we ordered a Prusa XL with 2 heads: one will extrude the part in TPU while the other will extrude the support in PLA, which should fall right off.

So since I told the slicer to avoid touching the bellows with the support trees, there's a lot of it going around it on the outside. And indeed the bits of parts that I managed to print so far seem quite stiff and nicely supported. But the problem is, the entire thing simply comes unstuck and flies off the bed when it becomes too heavy.