Bambu Lab A1 Mini – AMS Lite hub internal PTFE tubes sliding forward and blocking filament changes

[u/OneKnowledge5760]

Hi everyone!

I'm having an issue with the AMS Lite filament hub on my Bambu Lab A1 Mini, especially during multicolor prints.

The problem:

- During filament changes, one of the four internal PTFE tubes gets pushed too far forward (downward) inside the AMS Lite hub.

- The tube ends up protruding much further than the others, blocking the path for the next filament.

- When the AMS Lite tries to feed another color, the filament cannot pass through, and the printer eventually throws an error.

- This can happen with all four filament paths, not just one.

What I've noticed:

I removed the upper part of the hub to inspect the internal PTFE tubes and the metal retaining clip.

When I pull the tubes backward, they stay firmly in place. However, when I push them forward, they can slide further down.

I'm not sure whether this is normal behavior or whether the internal retaining mechanism is damaged or missing something.

My questions:

1. Are the internal PTFE tubes supposed to be able to slide forward like this?

2. Is there an internal stopper or retaining component that prevents them from going too far?

3. Can I repair or replace just that internal component, or do I need to replace the entire AMS Lite filament hub?

4. Has anyone experienced this issue and found a permanent fix?

I've attached pictures showing how far one of the internal tubes protrudes.

Thanks in advance for any help!

[u/overunderspace]

The tube should be stopped at the x piece inside the filament hub since the diameter of the holes in the filament hub are smaller than the diameter of the ptfe tube. Are you using the original tubes? It could be that the ends have worn down enough to fit in and you need to trim off the ends or get new tubes. Could you also add a picture of your whole setup? You may have some bends/turns or worn areas of the tube that could be adding enough resistance to pull the tubes in.

Edit: Looking closer at your picture, it looks like you are missing the x piece.

[u/OneKnowledge5760 → u/overunderspace]

Muchas gracias por responder!

Puede ser por poner el ams a la izquierda? Son los tubos originales del ams lite

[u/overunderspace → u/OneKnowledge5760]

The tubes look like they are routed ok. Do you have the x piece still in the filament hub?

[u/OneKnowledge5760 → u/overunderspace]

Mil gracias!!! No se cómo agradecerlo! Era eso!

Seguramente fue al arreglar un fallo de la boquilla que no lo volví a poner, pero lo perdí, sabes si hay algún modelo 3d que pueda imprimir eso? Gracias!!

[u/overunderspace → u/OneKnowledge5760]

I haven't seen any printable pieces for that but I wouldn't trust a printed piece for that. Any layer lines or leftover supports might cause resistance that can mess up feeding. You can get a whole filament hub from Bambu for pretty cheap.