Filament expansion

I’m using PLA and PLA-C, at 220 and 50 or 55. Bambu preset uses 55. Usually a printer prompt states 55 can cause clogging, if the prompt appears I change to 50. For the past few weeks the AMS can’t retract filament. Bambu wiki indicates filament expansion is the problem.

How is expansion corrected? I’m very new at 3D printing and have not been able to find a solution.

I can’t speak to the AMS problems since I don’t own one. However, I can speak to your interpretation of the Wiki. the 50 and 55 temps refer to the print bed temp. the 220 refers to the nozzle temps. I know of no filament that flows below 190c so this should be an obvious red flag when you’re reading the wikis.

When it comes to filament expansion, be cautious when reading information. Make sure it the wiki isn’t referring to issues caused by moisture, which PETG, PC, and other moisture-absorbing filaments are susceptible to. PLA isn’t prone to absorb moisture, so if you’re reading a wiki discussing filament expansion due to moisture, keep in mind that it won’t be relevant to your PLA use.

The points I’m making is that for the wiki’s to make any sense, you have to master the unique vocabulary of 3D printing. Otherwise, you’ll be doing a lot of guess work. Having said that, you should get accolades for at least doing your homework. Too many folks just throw up their hands.

Thank, I didn’t realize the vocabulary was so complex. I think what is happening is the filament end has started to expand when the print stops. I’m guessing it cools just enough to slightly harden before the spool starts to retract. To retract the filament I pull the filament as the retraction starts. It obviously pops free, than spool retracts just fine.

Does that mean the hot end is too hot? I suspect that is the problem. Perhaps I need to learn how to check the fan speed. Did have to replace the fan awhile back. Don’t remember if problem started right after that.

220c for PLA is right inside the strike-zone. I tend to favor 240ish because I find it flows better but I’m also more tolerant to stringing since most of my stuff is mechanical parts, not ornamental prints.

Not a big fan of using the AMS with any CF infused material. It’s quite rough on the printer just as is. I love the material, but it takes some special attention on the maintenance side. Specifically, the ptfe tubing takes a hit as well as the nozzles.

This being said, @olias is correct. The wiki info can be your best friend or worst enemy. Make sure you check multiple sources for accurate information.

As far as filament expansion goes, always make sure to purge any material with cf afterwards by flushing your nozzle with a bit of standard PLA. PLA is your friend. It is far less hygroscopic than most other filament materials and it is very easy to clean out of the nozzle. As filaments absorb moisture, they can expand. This expansion can be in diameter and technically, in length. This goes back to my personal philosophy that 3D printers hate two things very specifically: standing idol (unused) for a long period of time and secondly, cold. I’m not getting into a debate on the subjectivity of what ‘long time’ or ‘cold’ is here. Let’s assume 1 month and 30F.

So, keeping in mind that as materials heat up, they also expand, you have to accept that as they cool, they shrink. That’s fine. However, as the filament absorbs moisture it will want to grow. Inside the nozzle, if left for a long period of time, this may be problematic and you may unintentionally cause swelling leading to a clog. A good rule of thumb if you are concerned about this is to always unload your filament even if you don’t purge the nozzle afterwards with PLA.

I’m sure there are plenty of other tips on this, but abiding by the above has lead to 1000s (yes 10s of 100 hours) of successful hours of printing for me!

Good information.

In the current situation the AMS is trying to withdraw the filament as soon as the print finishes. I think it is just the tip end of the filament that is stuck. Would that indicate a problem with the hot end?

I can change it and see what happens.


@dixonsally, I think maybe it’s not clear what the issue is. Are you having trouble with the AMS not retracting completely? That’s a completely different issue from filament swelling in my opinion. The AMS is its’ own category of variables that could lead to unexpected issues. Please elaborate on what your problem actually is with your setup. We can help diagnose from that point.

The AMS motor overloads when trying to retract at end of using that filament. I’ve found that if I unwind enough filament to be able to hold on to it, tap retry, hold ams down with one hand, pull up on filament with other, until end in the filament pops free, let go of filament, the AMS rewinds perfectly. That consistently solves the problem.

I think the issue is the end of the filament is “attached” somewhere in hot end or extruder. I provide just enough additional pull to free it. I have no idea how to determine what is causing the filament end to “bind up” at the end of the print.

Nor, do I know how to determine where to filament is stuck.

Hope that clarifies the problem.