CC3D 72D TPU Filament keeps slipping out of H2D print head

Bambu Lab H2 Series Troubleshooting
1

Hi everyone. I have been trying to run dual-material prints on a very recently purchased Bambu H2D. The materials are TPU 95A and CC3D 72D TPU

Both spools are housed on the H2D Flexible Top Feed Rack and fed directly into the print head without PTFE tubing.

72D is on the left, 95A is on the right. 0.6mm nozzles for both. Print settings for the 72D are basically the TPU for AMS profile with specific edits to match the manufacturer’s print setting recommendations. Fan speeds are min-max 10%-40%, which I took from 3dfilamentprofiles
Both filaments are dried according to default TPU settings on the AMS HT before printing (18h @ 75C), and housed in the AMS with desiccants when not in active use.

While the first two prints had no issues, every print tried since then has had the 72D filament breaking inside the print head and slipping out of the top either during setup or the print, requiring it to be loaded again before a print can continue. The tip on the end of this filament often looks tapered. The H2D also seems to grip the filament very tightly between the pulley and extrusion gear.

I’ve tried printing at 220 (manufacturer range is 230-240C), but had similar printing failures. Not sure how low I could comfortably go before the filament doesn’t melt properly at the nozzle.

The latest print failure today came from an “extrusion motor overloaded” error, but since the filament was intact, I unloaded it. Here’s a photo of the end of the filament:

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Isn’t this length of the filament basically in open air between the gear and the nozzle?

What do you think is causing this, and what can I try to fix it?

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I try Tpu for ams. I think I printed with higher temperature as the layer bonding is bad with that filament.

So, maybe increase the printing temp? The lower the harder for extruder to push out filament. Especially printing lower than recommended temp range.

1 Like
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Hey Curler,

Though don’t see your previous replies anymore, I’ll answer them too:
Volumetric speed was reduced, yes. I used 3mm^3/s. Also, where’s the profile for 85D? I haven’t managed to find anything like it.

The top feed rack I’m using comes from the Bambu TPU printing guide, so I’m following the special instructions there too.

I’m not having troubles with filament coming out of the nozzle, actually. The problem is that it keeps breaking somewhere around the driver, so that the print head can’t pull more filament to reach the nozzle. I’m not sure if raising the temperature would help with that.

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Yeah, I was confused with D and A, and replied wrongly, so I deleted the other replies.

Tpu for ams is 68D, which is a pretty rigid tpu. You are printing 72D, which should be more stiff.

I was thinking when temp is two low, the motor can’t push the filament through, then the filament break around the driver.