Started on the TPU parts of my first chair build, doing the 0.6mm nozzle prints first, and noticing a lot of pitting on front side of the headrest, compared to the backside of the headrest. What gives?
Running the TPU profile on Makerworld, filament dried 70degC for 24hrs, and printing top-fed from back port of AMS-HT.
Comments and suggestions welcome, thank you!
I always thought that look was from wet filament but if you dried it for that long I would hope that isn’t the case. Were you drying while printing from your ams HT?
Also I didn’t have great luck when printing TPU from the AMS HT, it just didn’t seem to spin freely enough when feeding directly into the printer, that might be some of the issue you are seeing as well.
I got the TPU assist module from Bambu and that really helped make my TPU prints look so much better. What speeds are you printing at because even the seem at the back doesn’t look great.
What machine are you running and how is the TPU being fed to the machine/toolhead?
I’m printing with H2S, with TPU being fed from the back port of AMS HT directly into the toolhead, the AMS HT sits on a printed rack that mounts over where the glass top usually is.
Before printing out the headrest cushion, I printed the harness and little latch pieces with the same setup just fine. It’s when I did the headrest that the pits became so prevalent, but what’s puzzling me is why the front side is more affected.
Maybe speed is an issue. The headrest took just under 3hrs to print, but when I did an object dump into the “perfect TPU” file and sliced it again, the estimate’s a fair bit longer
I’ve dried that TPU at 70degC for another 24hrs in the meantime, and kicking off another print, see how it goes, and I do continue with the drying cycle while the print happens.
Have heard about AMS HT resistance issues, think I’ll go pickup one of those Polymaker single slot dryer box. I know cereal box mods exist, but it’s not easy finding a big enough cereal box in this part of the world, that’ll accommodate a filament spool.
Thank you for your help! I hope speed is the main culprit here.
What TPU are you using?
Since you are running the AMS HT and its not being used in the AMS function currently, you can have it continue to dry the filament while you run - just make sure NOT to mark rotate while drying, as that will cause issues…
Drying at 75 while pricing worked pretty well for the Bambu TPU 95a HF I ran. The Priline 98a seemed to be a bit more sensitive so I turned the temp down a tad to 65 instead of 75.
I’m running Bambu 95A HT, and yeah I see the TPU program’s drying at it’s default 75degC - I need to change that program on my Creality filament dryer. Kept on thinking it’s 70degC for TPU.
Luckily I’m not too careless, I did make sure it’s not rotating during print 
The Polymaker box is exactly what I use, I tried the HT and a cereal box mod but they just never spun well. Plus now I can dry in the HT and print from the Polymaker while drying another spool.
A couple of the settings I changed when printing the cushions with TPU Air were to print outer walls first and then avoid crossing settings. Maybe those will help with normal TPU on the cushions as well. I think 4ish hours sounds about right for High Flow TPU 95A if I remember right.
Great to hear Polymaker drybox’s a good candidate to print TPU from, where I am it’s constantly over 50%-70% humidity year round, so I simply can’t risk leaving TPU out in the open in any way.
I do have “avoid crossing walls” on, but still doing inner/outer because of slight overhangs, will outer/inner not affect quality of curved parts?
I didn’t have any issues with the outer/inner when I printed them but I can’t say there won’t be issues, I don’t know enough about it.
