After getting a couple of 3kg spools of PLA filament, I had to design a spool holder for use with my Bambu P1S and H2S 3D printers.
Unlike most spool holders out there, this one includes a fitting for a PTFE tube. Which prevents bad outcomes when the filament is tangled on the spool, which will happen sooner or later.
Spool dimensions: 52mm axle diameter, up to 305mm (12") outer diameter, up to 104mm (4.1") width.
For anybody looking at similar spools, the Fusion 360 CAD model, STEP and 3MF files are all on Github and MakerWorld
Update Feb'26 one of the recent Tangled spools I received is 104mm wide instead of the previous 100mm. So I updated the CAD model to version B6. Works with both old and new spools. Also includes updates that increase rigidity, improve reliability against spool dimensional / warping variations, and reduce the pulling friction experienced by the extruder:
- 6mm walls
- 5mm larger radius clearance
- twice larger axle-holding races
- plain bumpers against spool's inner cylinder
- 30mm higher tube holder for less sideway pull on filament
- 2.6mm filament feed-through hole at the bottom of the fitting hole to prevent tube pull-through
- horizontal tube holder for smoother unwinding when spool is full
- split ring support for the axle to facilitate breaking it off
- cleaned up CAD timeline
Happy mega prints to all !
CAD Model
Designed to fit on a 250mm large plate, for the box's longest dimension. 240mm in height.
Settings:
- PLA, 0.4mm nozzle, 0.24 layer height
- 3 walls, 3 top, 3 bottom
- 15% Adaptive Cubic infill, Infill Combination enabled
- Support enabled, Critical Regions Only (only used for the threaded fitting hole)
- Seam alignment set to Back for the Box & Tube Holder, Random for the Axle (for smooth rotation, otherwise the seam line creates a bump every turn of the spool)
- takes ~8.5 hours, 520g grams
Plate:
Once printed, remove the base support from the axle:
The parts were actually printed from a 3kg spool, using a quickly-put-together wood prototype and a 3D printed axle that helped validate the concept and dimensions:
Assembly
Just glue up and slide the Tube Holder's dovetails into the Box's top rails.
Install the PC4-M10 pneumatic fitting and some length of regular PTFE tube going to the printer.
Do not use the spool holder without the fitting and tube. This prevents the printer from dragging the spool across the desk and up to the intake when the filament is tangled in the spool, which happens sooner or later. Such an event can also dislodge the spool and have it roll away and unwind in the room.
But not so with this holder. The fitting and the tube ensure that the pulling force from the extruder exists only between the fitting and the spool.
Once the assembly was completed, the rotation was very smooth with little friction despite the spool's weight. There initially was a squeak when the spool rotated, though. Came from the axle rubbing inside the casing grooves holding the axle. A tiny bit of PTFE / dry lube took care of that, soap might work too.
H2 Issue with External Spool
After consuming about six 3kg spools using this holder on my P1S, I thought that using it on the H2S would be as uneventful.
Nope, gave up 2 days later after dozens of 'filament stuck / not extruding' interruptions. Every 10 to 30 minutes the printer would throw that warning, although the spool was spinning freely in the holder.
Made no sense since:
- no false detection ever with P1S
- I was using the newer B version of the holder that presents even less friction than the A version initially used with the P1S
But then I removed the Bambu 4-in-1 PTFE Adapter, connected the spool tube directly to the inlet in the back of the printer, and completed an 8 hour print with no issue.
So is the adapter introducing friction or weird quirks ? Doubt it, as pushing / pulling a piece of filament through is pretty much frictionless and smooth:
Instead, it seems to me that the H2's integrated filament buffer might be the culprit, and that the adapter is just the camel that broke the straw 🤷
Indeed, on P1 the AMS's filament buffer is bypassed when using external spools. But it is always in series on H2, AMS or not. And I noticed on several occasions weird stiction / grab-and-release reactions from it when manually feeding filament through.
My hunch is that with external heavy spools and a long feeding tube, since there is no AMS pushing the filament, the H2's extruder now experiences more pull-catch-release hiccups from the buffer. Which might erratically trip up one of the feed or nozzle pressure sensors. The occurence rate might vary depending on spool weight, external tube length, specific printer, etc.
If this issue still happens for some people, even without the 4-in-1 adapter, one could also try directly feeding the filament to the toolhead's intake, like when printing soft TPU. That should solve it.
But it's definitely an unexpected and annoying issue. If confirmed, maybe Bambu would be able to issue a firmware update that filters out such random triggers ?
3kg Spools
Dimensions:
Blatant shout-out to Tangled who invested in equipment and a biz model to make high quality PLA at $10/kg in the US:
Tangled's post on temps: www.tangledfilament.com/post/raise-your-temp-and-or-slow-your-speed-how-to-print-pla
So far, functional parts printed with it look identical to Bambu PLA, but I haven't tested overhangs and bridges extensively yet. The only drawback so far is the lack of a No-Spool Refill ordering option or simple way to ship the empty spools back to Tangled for reuse.
Also, the roasted-almond smell when printing is stronger than with Bambu's Basic PLA, probably because of the higher nozzle temp. So make sure to ventilate the room or filter the fumes as even PLA emits toxic compounds
No idea if the Tangled spool's dimensions will vary over time, or if spools from other suppliers are the same size. So make sure to double check. Update Feb'26 well, now we do know: they do !
Time to crank out parts like daily baguettes out of a bakery !
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