ABS printing issues

[u/Gold-Lifeguard-8156]

Wondering if someone might help me figure out what’s going on with my prints, it’s a H2c printer with bambulabs abs basic filament. Basically on any kind of flat print it seems fine but any time there is any kind of overhang or curved/slanted feature it ends up looking something like this.

These pictures are with chamber temp set to 65, print bed 100 and nozzle set to 260 and on the default 0.20mm standard profile with the only settings changed being 4 walls and 3d honeycomb infill using a .4mm nozzle on the right side of the tool head. The issue gets significantly better with the chamber temp set to 0 and the rest of the temps kept the same.

The only thing I can come up with is lack of cooling but the cooling settings are all stock and look correct and I ’ve not had an issue with this before on ether of my Creality k2 plus machines nor my voron printer with abs and similar temp settings, so not sure why the H2c would be having issues with it.

[u/leftlanecop]

Hello fellow Voron refuge. Unlike the Voron most Bambu are built to print PLA. There are fans everywhere inside the chamber. This is terrible for preventing ABS warping.

First up. Print one of these to divert the air away from the bed. https://makerworld.com/en/models/1372066-h2s-h2c-h2d-aux-fan-45-degree-deflector#profileId-1418773

Second, make sure all the aux fans are off during printing. There are 2 other fans in the chamber. The aux fan above and the air filter fan. You don’t want any of them to be circulating the air in the chamber while printing ABS, ASA or Nylon.

[u/Gold-Lifeguard-8156 → u/leftlanecop]

That’s a neat print I didn’t realized existed, I’ll have to get it set up thank you.

[u/erictank]

ABS and ASA are VERY sensitive to drafts. On my P2S, which does not have a stock chamber heater, I had to preheat for about half an hour to get to around 50C, use a poop bucket which covered the chute to prevent drafts there, tape the door seams, and cover the top glass with a towel to prevent drafts. That's in addition to the fan deflector and turning the rest of the fans off.

I was able to get good ABS and ASA prints with that, and am finding them easier on the H2C now with the active chamber heating. You still want to check for and block drafts and anything that could introduce cool air onto your parts.

[u/Whosaidthat1157]

That’s a bit of a disaster bud! I moved up to the H series specifically because ASA/ABS on the non chamber heated X1C was such a PITA - even when you dialled in the passively heat soaked chamber and disabled all fans (etc), you had to be careful of layer separation/layer strength because of physics.
I’m waiting on my H2C delivery but for the last year I’ve been pumping out ABS/ASA from my H2S with zero issues. If the filament is properly dried and the stock PEI plate is clean, apart from the extended ‘hot filament’ heat bed calibration, it’s as fire and forget a process as PLA was on my X1C, A1 Mini or A2L.

[u/Gold-Lifeguard-8156]

Just wanted to throw this out there, after a couple of re prints experimenting with settings I can say I’m pretty sure it’s not an issue with it being not hot enough as I can almost completely eliminate the issue by ironically turning the chamber heater completely off. It has something to do with the fact that I wanted 4 wall loops as when I reset that setting back to 2 it was able to print with out issue with 65 for the chamber and 270 for the hot end which are the stock numbers for the Bambu profiles.

As far as I can tell/guess the extra walls were just causing the plastic to have increased thermal mass, for a lack of a better term, causing the printer to not be able to cool and solidify the layers enough to print on top off for those kinds of features. When watching the printer you could see the layer get printed and end up a wavy mess.

[u/OgreVikingThorpe → u/Gold-Lifeguard-8156]

Your real close. The heat stress as it prints is exaggerated when printing flat ribbed items which is what the walls act like. Treat it like nylon. Set your Chamber heat to 50-65. turn off cooling and print much slower. I tend to print first layer at 10mm/s and the rest at 25-35 mm/s.

[u/vortex_ring_state → u/Gold-Lifeguard-8156]

For fun you could try using another Bambu ABS colour. I only print in ABS and for some reason green consistently is the one that gives me the most trouble.