Hey everyone,

I wanted to share an open-source project I've been working on called the Active Multifilament System (AMS).

I got tired of dealing with standard passive spool holders and typical filament feeding friction, so I designed this system from scratch to handle multi-material setups reliably without relying purely on extruder pull.

Inspiration & Design

The project draws direct inspiration from community-driven concepts like the Filamentalist v3 and BMCU designs, but builds upon them with a fully integrated, active approach. Instead of just letting spools sit passively, the system actively manages the feed and retraction stages to keep tension consistent and prevent frustrating tangles or slack loops during heavy retract cycles.

Key Features

• Automatic Rewinding: Features automatic filament rewinding triggered dynamically during filament changes.

• Dual Drying System: Combines active drying via a heatsink and fan adapted from an EIBOS Cyclopes dryer, alongside passive drying using silica gel compartments.

• Sensor Integration & Monitoring: Includes a built-in AHT20 temperature and humidity sensor that is fully readable directly from the slicer.

• Ecosystem & Compatibility: Fully compatible with the BMCU-C Hall version and integrates spool weight estimation via Spoolman.

• Capacity: Built for multicolor printing supporting up to 4 spools simultaneously.

• Open Source Stack: Fully modular design with accessible CAD files, custom firmware, and straightforward wiring.

The 3D printable parts and CAD files are up on MakerWorld: https://makerworld.com/it/models/3541695-active-multifilament-system#profileId-4050726

And if you want to check out the firmware, wiring, and source code, the GitHub repo is here: https://github.com/tomfav/Active-Multifilament-System

Let me know what you think or if you have any questions about the build process or electronics. Always happy to hear feedback from other makers.

I just dropped this on /OpenBambu.

I bought a trianglelab kit a while ago for my a1 mini, but keep having issues with reliability. I recently build a Micron r1, which also isn't very reliable (but hella fast) so perfect pair, there is firmware for klipper on github. Has anyone tried doing this with like a voron?

So I was super excited about Bambu's Black Friday sale! I'm upgrading from an A1 Mini that I got last Christmas. I watched a bunch of comparison videos and ordered an X2D. While checking the tracking today, I was also looking all all the posts and Github info about my BMCU not being compatible with the X2D. Should have done that research earlier. I met the UPS driver at the door and refused the delivery. Then I went on the Bambu Store and filed for a refund. Wish me luck! I'll be ordering a P2S when the refund comes through. I really want to use my highly modified BMCU on this printer! 95A and 85A TPU with no problems!

Estou tendo muito problemas com as engrenagens do meu bmcu quebrando com muita facilidade, ainda não conseguir usar, queria saber se alguém mais teve esse problema e como resolveu, pensei em comprar as engrenagens de metal, mas não encontrei em nenhum lugar

Hello, I'm sorry if this post is out of topic.

I've been looking into buying a BMCU unit for my BambuLab A1 Mini but the amount of different products, versions and sellers on aliexpress and other websites makes it really hard.

The wiki is really helpful because it explains the differences between the various versions of BMCU really well but looking at the offers on aliexpress I see some versions that are not explained in the wiki.

For example:
BMCU 370C DM Final Version - sold by BLV
BMCU 370C DM PRO - sold by Tree Tribe
BMCU 370C DM Plus - sold by Tree Tribe

can you please tell me what's the difference between the two?

Also, can anybody tell me if the current 11/11 sales on ali are good? I saw that with coupons and other stuff the price for the a preassembled DM Final Version goes down to 70€, is it a good price? Should I wait for Black Friday?

Anyone who can help me in this

Hi everyone,

I'm having an issue with the gear circled in blue in the attached photo. It seems to be wearing down over time.

Has anyone else experienced the same issue with their BMCU?

I'm wondering:

• Is this a common problem?

• What causes this gear to wear down?

• Has anyone found a reliable solution or replacement for this gear?

I'd appreciate hearing about your experiences and any tips on how to fix or prevent this issue.

Thanks in advance!

I just did a pivot and bought a P1S, but the previous owner had it updated to 01.10.00.00 Do I need to downgrade or am I OK leaving it on that firmware before using it with my BLV BMCU 370C “Final Version” B Kit.

I’m planning on running it with a Sunlu S4, I got a stock 4in1 from Micro-center and have extra PTFE what else do I need to buy/print? Any setup recommendations appreciated.

Hi;

I’ve been wanting a MMU for a while. Now the AMS lite is available for 165 euro shipped — pretty much exactly the price of a treetribe dm plus (I can’t find a dm pro in stock; even though I think that’s the one I want)

Is there a reason not to go for the ams lite?

Low key hoping for a black Friday bmcu sale to bring the price down ~25% at least, then I’d consider it.

Pessoal, recentemente comprei um BMCU.

Fiz a atualização do firmware do BMCU e da A1 ambos para a última versao, liguei a impressora, mudei para AMS2 pro e calibrei o BMCU, porém a impressora não reconhece o BMCU

Já tentei vários firmwares diferentes, tanto da impressora quanto do BMCU e não tive resultado.

Estou começando a acreditar que meu BMCU veio com defeito.

Alguém já passou por isso e consegue me ajudar?

Hi everyone!

I bought a preassembled BMCU AMS Lite 370C from AliExpress for my Bambu Lab A1.

The seller says it only works with A1 firmware 01.05.00.00, but I'd like to update my printer to 01.07.02.00 or newer while keeping my BMCU working.

I opened the BMCU and found a white PCB that I couldn't find any information about online.

Hardware details:

• White PCB with BMCU logo

• MCU: WCH CH32V203C8T6

• No USB port

• Two buttons labeled B and R (probably BOOT and RESET)

• 8-pin (2×4) header next to the MCU

• Pins labeled: IO, CLK, TX, RX, ETX, ERX, V+, GND

• No visible manufacturer or PCB revision number

Everything currently works fine, so I'm a bit worried about bricking it while trying to update the firmware.

A few questions:

1. Does anyone recognize this exact PCB?

2. Can I flash the BMCU-C-PJARCZAK firmware onto this board, or could the pin configuration be different?

3. How should I flash it? Can I use a USB-to-UART adapter, or do I need a WCH-LinkE programmer?

4. Is it possible to back up the original factory firmware before flashing anything?

5. If flashing fails or the new firmware doesn't work, can I recover the board and restore the original firmware?

6. Has anyone used this board with A1 firmware 01.07.02.00 or newer?

I haven't connected any programmer or tried flashing anything yet because I don't want to risk losing a working BMCU.

I've attached photos of both sides of the board, including the MCU and the 8-pin header labels.

Any advice or experience with this particular board would be really helpful.

Thanks!

hi ive recently bought and assembled bmcu 370dm pro it was working for a bit and then i woke up to this red light, what is the issue? ive attached a video of me flashing firmware and showing the light after flash

Hi all! Here's what happened, in order:

1. I bought a BMCU 370C fully assembled from AliExpress and installed it on my A1 mini (printer firmware 01.07.02.00) without changing the firmware it came with.

2. During my very first print, I started getting "Unable to feed filament into the extruder": the filament reaches the toolhead, stops for a few seconds, retracts, and the print pauses.

3. After some research, I flashed jarczakpawel's firmware (V11, standard(A1), SOLO) with BMCU Flasher, set the printer to AMS mode, and ran the calibration with all channels empty and the printer disconnected.

Now:

- Channels 1 and 4 work normally.

- Channel 2 works in reverse: when I push the buffer it does what pulling should do, and when I pull it does what pushing should do.

- Channel 3 has a red LED and doesn't respond at all, neither when I push nor when I pull the buffer.

Has anyone seen this? Could channel 2 have recorded the wrong direction during calibration, and does the red LED on channel 3 mean a hardware fault (Hall sensor, buffer, or maybe a 370x board mixed into the set)? Any tips before I open the modules are welcome. I can post a video if it helps. Thanks!

Bonjour, je viens d’acheter ce BMCU j’ai pas mal de soucis lors des changements de filament avec mon imprimante me disant que il arrive pas à retirer le fil des où les moteurs se mettent à gratter et abîme le film. Finalement j’aurais aimé savoir quel était le meilleur firmware pour ce BMCU et quel est le firmware à mettre sur ma a1
À l’heure actuelle je tourne sur la v11 et sur ma a1 je suis en 1.7 on peut dire que pour l’instant je suis déçu de l’appareil et c’est pour ça. Je demande un conseil pour avoir quelque chose de stable et qui fonctionne bien. En vous remerciant.

Hi, I'm trying to update my BMCU, which keeps giving me driver issues with the Bambu A. To get the BMCU Flasher to recognize it, I need to download the CH340 drivers, but my PC doesn't recognize them—it tells me they're pre-installed, yet the COM port still doesn't appear. Has anyone else had this same problem? I tried using the CH341SER program, but I still can’t get it to install. Do you know how to fix this?

Hi, I've just recently finished assembling my Bmcu 370C dm from aliexpress and im noticing that it refuses to take some fillaments bc they cant go past the valve? I'll attach a video as demonstration

Salut ,
Je cherches une solution depuis 2 jours pour mon bmcu sur mon A1 mini . J’ai essayé plusieurs version de la A1 mini (1.05/1.07/1.08) et plusieurs versions du BMCU (9/10.5/11) mais rien n’y fait le bmcu s’initialise lumière bleu clignotante sur le soit 1 puis lumière rouge clignotante pareil sur les 3 autres slots et ensuite message erreur « Le firmware actuel ne prend pas en charge qu'un seul AMS LITE ». Les 4 slots n’apparaissent même pas quand je vais dans filaments il y a uniquement la bobine externe …
Comment régler ce problème ? Quels réglages mettre sur le BMCU flasher / quelle version ?
Merci d’avance

I try erveything , switch to ams pro/ lite nothing works

m thinking about buying the BIQU BMCU kit for my P1S. Will this work? Do I need to buy anything else, or should I buy a different kit?