I recently upgraded to the H2S, coming from a Qidi machine. On the Qidi I exclusively printed with CF filaments (ASA-CF/PET-CF mainly) and had zero issues with it handling any brittle filaments. However, on the H2S during the load from external spool, it moves the print head to the far right thus bending the PTFE tube so severely it snaps the filament. I’ve tried now with ASA-CF, PET-CF and PAHT-CF and the same thing happens every time. All spools are dried to spec. Even tried with new spools right out of the packing.
I don’t have an H2 but in other printers with constrained PTFE paths, you can generally solve this by printing a “glass riser” which sits on top of the machine, under the glass, and gives an extra inch or two to the top space where the cable chain runs around in. Then, you can unhook the ptfe and let it live in the space above, which gives it plenty of room to do a lazy angle down into the extruder. See if one’s made already
I got the filaments to load by removing the tube from the first clip and hand guiding it with the glass top off while it loads. After that the print is fine. I’ve logged this with Bambu support to see what they say. I found a riser STL so will print that tomorrow but even with the glass top off, the tube droops below the chain and I don’t see a need for the riser really but maybe I can try repositioning the clips so the tube stays above the chain. We’ll see…
The riser generally contains the new porthole (or you can model that, use a fitting if youre doing it yourself) so that it enters the machine an inch or two higher, which fights that derpy ptfe droop. H2 being bigger though might need a ziptie somewhere
This aspect of the H2S really surprises me. It’s well known that CF-filled filaments tend to snap if they’re forced through sharp bends — so how could Bambu’s designers have overlooked something like this? Really strange.
In fact, on the H2D they recommend using CF filaments in the left hotend specifically because the PTFE tube has a gentler curve. I find it very unusual that this wasn’t taken into account on the H2S.
I thought the same thing, surely this can’t be an oversight. I did log it with Bambu support though so will see what they say (guess is they’ll just say move or lengthen the tube).
I don’t mean to offend anyone — advice is always welcome — but printing a riser for the glass seems like just a workaround to me, a way to bypass a problem which, if real, is serious and needs to be fixed at the root by Bambu. Straight out of the box, it’s unacceptable for a machine like the H2S to suffer from this kind of issue.
I agree with you. The bend in the tube is almost 90degrees and we all know most engineering filaments break up to 70deg, even a lot less. Saying that, I don’t see any chatter about the issue elsewhere so I don’t know if this is just a defect on mine or is more widespread.
Here’s the video I sent to Bambu support. Looks worse than in the pic above lol.
Sadly, it has to be said — a workaround is actually needed, as BambuLab itself admitted: you have to leave the PTFE tube free to avoid sharp bends. Really disappointing for a machine of this caliber.
I won’t defend bambus choice of tool head design but this is also the very extreme end of the spectrum, pet and paht cf tend to be the most brittle materials you can possibly squirt thru an fdm machine. It’s not tooooooooo unreasonable to do a small dance for it
I didn’t see that guide so thanks for sharing. Pretty sure I tried the spiral trick anyway but once I’m done printing the riser I’ll give it another go and see if both solutions work.
Remove the ptfe from the buffer/chain and use the bottom slot of the toolchain that that PTFE uses. Use a long ptfe through the tpu slot (you will need to put a blocker on the tube, I used fabric wiring wrap tape, but could use a PTFE connector or w.e. else, so it won’t slip out the back as it moves around)
Best way to see if it’s long enough is to move it to the front left. It should just about be touching the top glass when parked there (yeah, that long). After getting the length right, then put the tape/w.e. on
I haven’t had issues doing it this way with PET-CF or ppa-cf
Oh cool. Thanks for the pics that really helps. I’ve been using a riser but it’s not perfect. I’ll give your solution a try this weekend. Appreciate it!
