PTFE (external) tube lengths - AMS Pro 2 & HT (Im upset!)

Bambu Lab H2 Series Bambu Lab H2C
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Hi All,
Hoping someone has some advice before I lose my temper! :enraged_face: Long story short, I’ve re-arranged my ‘workshop’ so that my 2x AMS Pro 2 units and my 2x AMS HT units sit under my H2C. My workbench is approximately 1m high, with the H2C sitting on top of it. Bambu’s ‘suggested’ PTFE tube suggestions are either ballpark or very hit and miss. My 2x AMS Pro 2 units have PTFE tubes that run upwards into my H2C and are approximately 1.5m in length. They work fine. Occassinaly I will get resistance errors, but the filmanet always loads. Never a ‘major issue” and never a failed print or failed filament load.

My AMS HT’s however, are something else. No matter the length, I can’t get the filament to load. The filament reaches the toolhead/nozzle.. filament sits in the nozzle for a few seconds and then retracts back into the AMS HT spool. I cannot, for the life of me, get the filament to load. The PTFE tubes for my HT units are a shorter than for my AMS 2 Pro and wont work, but the longer tubes for AMS 2 work without issues?

I appreciate that the PTFE tubes cannot be an infinite length, however not everyone can have the same setup. Living areas, rooms and space where everything sits etc differs to each persons requirements, so having a suggested length of 900mm should not be a 1 size fits all. Especially considering how long my AMS 2 Pro tubes are and work no problem. Now, I havent been in the 3D printing game for long, just under a year to be exact, so I don’t know if this is by design and across all vendors or just a Bambu thing?

Anyhow, my small rant is over, so if anyone has suggestions on how I can get my HT’s to accept the filament, please let me know.

Thanks everyone!!

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Place HT units on top of the printer and cut short PTFE feed tubes.

Test the filament feed into both feeds (in case one works and the other does not).

If success - adjust the tube longer until you find the sweet spot for your setup.

If fail - examine the HT unit.

I have two H2 Series printers and run AMS2PROs and HTs on both. Those stupid tubes can be really temperamental. And the external “assist” gadgets the BL released for TPU and such made them even worse (in my case). I just did the test posted and haven’t had an issue since. No idea why some are cool with longer tubes and some are a bit more restrictive. I run PLA and PETG only. So it’s really got nothing to do with filament. I considered running TPU on the H2 Series printers, but that got tossed when I worked with the external “assist” gadgets. Nope. I wish you the best. When they are dialed in, they are incredible printers. Worry free. Enjoy.

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I’m going to make a suggestion for you to consider.

It’s actually about timings. The printer asks for the AMS to provide filament, if the filament doesn’t present itself quick enough to the printer then the printer timeout.