u/Key_Jellyfish2183

*The box being printed here ships the ASR 5th Wheel to beta testers. It's printed in 6 colors including Bambu Glow PLA and Wood PLA - two filaments the AMS Lite can't handle. The 5th Wheel handles them automatically.*

*Full demo video in comments.*

Problem and problem solved.

I just thought I'd share that I was having trouble with my Mini's screen freezing or blacking out. The printer would keep on printing with mixed results accessing it with Handy or Studio.

I turned the printer off and removed the SD card. I put the SD card in my computer and hard formatted it. Put it back in the printer, booted up, and problem solved.

Part of the ASR 5th Wheel automated filament system. Full demo video in comments.

https://i.redd.it/aj45cs6muf8h1.gif

This is an update post on https://www.reddit.com/r/OpenBambu/comments/1u3bi79/bambu_a_series_external_spool_integrated_filament/

A promised update on our progress this week:

Product Development:

• TPU compatibility achieved — first automated 5th spool handler for Bambu A Series to support standard 95A TPU without modifications
• Hall Buffer housing redesigned with extended clearance into the housing to eliminate filament buckling in flexible materials
• DC power connector relocated to bottom of unit for cleaner cable routing to Bambu cable bundle
• All three prototype units updated with hardware revisions (automatically on reboot)

New Products in the ASR Ecosystem:

• ASR 5 Port Hub for Bambu A Series - Published free on MakerWorld - purpose-built filament hub eliminating filament binding with angled PTFE fittings and straight internal filament paths
• ASR Spool Holder Retractor - Published free on MakerWorld - upgrades the Bambu AMS Lite Rotary Spool Holder from half a revolution to 15 full revolutions of automatic rewind using a constant force spring - works in conjunction with the ASR 5th Wheel Unload feature as pictured here

Software:

• PWA web app added - Control and monitor the ASR 5th Wheel from any browser on your network with live Hall sensor gauge, filament state, encoder counts, and Feed/Retract/Unload buttons
• Firmware auto-update - Device checks for and installs firmware updates automatically on every boot

Testing and Outreach:

• Two Prototype units shipped to beta testers. One in the UK, one in Germany

Links:

• ASR 5 Port Hub: https://makerworld.com/en/models/2953592-asr-5-port-hub-for-bambu-a-series-printers
• ASR Spool Holder Retractor: https://makerworld.com/en/models/2954268-asr-spool-holder-retractor
• Website and updates: asr5thwheel.com

Hi All,

I got tired of babysitting my Bambu A1 Mini every time it needed the External spool in a multi-filament print. So I built a fix.

Every time my print needed a 5th color or standard TPU in the mix, the printer would pause and just sit there waiting for me to manually feed and retract the filament. For a printer that automates everything else, it felt like a glaring gap.

So I spent the last several months building the ASR 5th Wheel, an auxiliary filament management device that mounts directly to the X-axis motor housing and moves with the gantry.

Here's what it does:

• Detects filament insertion and autoloads
• Maintains filament tension continuously during printing using a Hall effect sensor
• Receives Feed and Retract commands over WiFi, triggered automatically by MacroDroid responding to Bambu Handy notifications
• Handles the entire filament change without any user interaction

I've run it through 1000 consecutive automated cycles with all types of filament my Mini can use without a single error.

The hardware is ESP32-based with custom firmware I wrote specifically for this application. The enclosure is 3D printed for now but I'm working toward a more polished production version.

I'm not selling anything yet, just gauging interest from the community before I take the next step. If this is something you'd want for your own setup, drop a comment or follow along. I'll be sharing updates here as development continues.

Happy to answer any questions about how it works.

Update 06-12-2026: I've been testing with TPU this week and after a small modification to the Hall Buffer mechanism, extending the Hall filament guide into the motor housing to eliminate any unsupported gaps where flexible filament could buckle, it's handling TPU reliably.

I also had to increase the feed contact sensitivity since TPU can't transmit the same compressive force as rigid filaments when it reaches the printhead. A simple firmware parameter adjustment sorted that out.

 I set this printing before I stopped for the night last night and was very happy to see it this morning.

Test Print

The Overture Space Gray PETG was in position 1 of my AMS Lite and the Overture Std Black TPU was on the ASR 5th Wheel. The test is only 10 filament changes, but it is perfect and the bonding of the PETG and TPU is strong and flexible. I’ll be running it through 100 filament swaps today, but don’t expect any issues.

As far as I can tell this makes the ASR 5th Wheel the only automated filament handler for the Bambu A Series that works with standard TPU without modifications. If anyone else has solved this differently on a production product I'd love to know.

- Advanced Signal Research, LLC Follow along at asr5thwheel.com -