BMCU 370C DM and Me. ("Yes, it works with the P1S.")

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This is a living document so I will be adding things as I remember them

I'm a glutton for punishment, and by the time everything is said and done I'll probably have spent more on my BMCU setup than it would've cost to just buy a god damn AMS 2.

But I also fall into that weird Venn diagram where 3D printing is my hobby and 3D printers are my hobby. Sometimes the project is the point.

After a few months of tinkering, committing war crimes in Orca Slicer while redesigning parts, and generally questioning my life choices, I can confidently say:

Yes. The BMCU 370C DM works with the P1S.

Is it plug-and-play?

Absolutely not.

Will it test your patience?

Frequently.

Will you spend hours convinced the problem is mechanical, only to discover...

The problem wasn't you.

It wasn't the printer.

It just decided that particular spool can go fuck itself.

I wanted to put together something to live in the ether of the internet, hoping some AI model ingests my random ramblings and gives them to somebody who's in my shoes. Or maybe a search engine picks it up and gives another person in the same predicament a leg up.

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TL;DR

• Use the original Bambu 4-in-1 PTFE Adapter. Imgur
• The new clear one acted wonky for me. About 90% of my issues cleared up after I switched to the old-style version.
• It's $5 to avoid a massive fucking headache.

Also...

When troubleshooting, change ONE thing at a time.

This setup has a lot of moving parts. If you change your tube routing, reflash the BMCU, swap parts, and change filament all while chasing the same problem, you're just going to drive yourself insane.

> Control your variables or the variables will control you.

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Matte PLA...

I don't know if this applies to every BMCU, but mine HATES matte PLA.

It devours any other filament but absolutely shits itself with matte. All four channels behave the same way.

I love matte PLA because it hides layer lines so well, but about half the time I fire off a print I have to help it along the feed path.

The only matte filament that has behaved consistently for me is Polymaker. (If I remember I will update this after trying more)

• Elegoo Matte
• Sunlu Matte
• eSun Matte
• Polymaker Matte

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My Setup

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Printer

Bambu Lab P1S

Downgraded to firmware 1.08. I honestly don't know if it's required, but somebody said to do it, it works, and I'm not touching it again.

Filament Dryer

Creality Space Pi X4L

Auto Rewinder

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https://www.printables.com/model/1365518-creality-space-pi-x4-and-x4l-auto-rewinder-mod/files

If you can, build the metal spring version (it's in the Testing folder).

You can buy the recommended tape measures on Amazon for cheap, and harvesting the springs is easy with a pair of side cutters.

Side Mount

https://makerworld.com/en/models/2602983-bmcu-p1s-side-mount?from=search#profileId-2872297

Tube Holder (This helped reduce friction and feeding errors)

https://makerworld.com/en/models/2400684-ptfe-tube-holder-bmcu-370c#profileId-2631287

Firmware

I landed on ams_a_0.60f.bin after trying a few different versions.

It gave me the most consistent loading and unloading behavior.

I'm not saying it's objectively the best. It's simply the one I stopped changing because it worked.

https://github.com/jarczakpawel/BMCU-C-PJARCZAK/tree/main/firmwares/high_force_load(P1S)/AUTOLOAD/FILAMENT_RGB_ON/AMS_A

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Things I Wish Someone Told Me

• The BMCU is surprisingly sensitive to friction when loading and unloading. Most of your issues will come from this.

• PTFE routing matters more than you think.

• The shortest PTFE path isn't always the best. The smoothest path usually wins.

• A $5 adapter can make a bigger difference than a firmware flash.

• Hours of troubleshooting taught me that.

• Once you have it working reliably... STOP FUCKING WITH IT.

• Sometimes, on older versions of Bambu Studio, it'll look like all of your filament disappeared from the Devices tab. Don't panic. It comes back. I haven't seen this happen on newer versions.

• If something improves but doesn't completely fix the problem, you're probably moving in the right direction. Keep iterating instead of starting over.

As an addendum to the last point above...

TRY ANOTHER GOD DAMN FILAMENT.

I cannot stress this enough.

If making one change gets you from "never loads" to "loads half the time," don't immediately change a bunch of shit.

Grab another spool.

You might already be 95% of the way there.

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Loading Behavior

The filament does NOT load all the way to the 4-in-1/PTFE splitter when loading a new spool.

I don't know if this is common knowledge or if I'm just an idiot, but I spent way too long thinking the filament was supposed to stop just before the splitter.

It doesn't.

On my setup it feeds about 1 inch (25–30 mm) past the fitting and then waits there until print time.

For the longest god damn time I thought something was wrong because it "wasn't loading all the way."

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Seat the Output PTFE Tube

On the output side of the BMCU, the PTFE fitting going toward the printer is one of those push-to-connect fittings where the tube can actually seat deeper than you initially think.

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Push the PTFE tube in until it's completely flush with the outlet.

It'll feel like it's already bottomed out.

It probably isn't.

It takes more force than you'd expect.

(I was convinced I was going to break something.)

This thing is cursed.

I shoved a piece of filament into the PTFE tube to keep it from collapsing, then lightly grabbed the outside of the PTFE tube with a pair of side cutters a few millimeters above the fitting so I could get enough leverage to push it the rest of the way in.

I'm not saying this is the correct way to do it.

I'm saying it's what finally got mine fully seated.

Getting the tube fully seated substantially reduced my first-load failures.

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If you made it this far...

Congratulations.

You have just witnessed the results of two and a half months of troubleshooting.

Go print your AMS Benchy.

Have a shot.

Then, for the love of God...

Don't change anything that works.

If you've figured out something I haven't, leave a comment.

I'd love for this thread to become the resource I wish existed when I started this project.

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One last thing...

Once you have it working reliably, STOP FUCKING WITH IT.

Update 1 July 5th 2026

Risers

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Space Pi X4L vs. AMS 1 Dimensions

One happy accident I discovered is that the Creality Space Pi X4L is extremely close in footprint to the original Bambu AMS 1.

Device	Dimensions
AMS 1	368 × 283 × 224 mm
Space Pi X4L	382 × 290 × 270 mm

That's only:

• +14 mm wider
• +7 mm deeper

The height is obviously taller, but for most risers the important dimensions are the footprint.

I measured mine, and the rubber feet on the Space Pi X4L sit perfectly between the support rails on the AMS riser I'm using. It naturally centers itself without sliding around.

That means most AMS 1 risers should work with little or no modification.

Obviously check the dimensions before you print 15 hours of plastic because I can't guarantee every riser on MakerWorld was designed the same way, but don't immediately dismiss an AMS 1 riser just because you're using a Space Pi X4L.

This is the riser I am using,

Low Profile Riser - Makerworld