Continuing the discussion from New user - need diagnosis help - under extrusion or xy problem?:
So last time, I managed to fix this with a full factory reset (after trying eveything else I could think of). I’ve swapped from TPC back to PLA and I’m getting the exact same artifacts again. Does anyone know what’s happneing? I don’t want to do a factory reset each time i swap from TPU to PLA.
I haven’t done this on a P series as I try to keep my TPU on the A series I have.
However, I have never had a problem when swapping back and forth multiple times a day.
I remember swapping at least 5 times on the same day.
I only had to remember to enable/disable the AMS option in the print dialog.
The thing that confuses me is it’s something that is fixed by a factory reset. And is only an issue when going from TPU → PLA and not the other way around.
A screenshot of whatever you see that shows use whatever you see that is stopping you would be useful.
Is the problem on Bambu Slicer or the printer?
Sorry how do you mean? Being blocked?
Sorry, if not clear, I rewrote it, is that any better?
If you check the orginal thread linked you can see the problem. The problem is with the prints, they come out… wonky. The slicer seems fine.
I tend not to enjoy reading other threads to understand this one.
I have though.
I can confirm I have never experienced this situation.
Well thank you for doing so. Hmmm I have no idea what it could be then.
That’s an odd one for sure. Not sure why it’s doing that, but maybe we can figure it out. I’ve never had issues switching between various filament types (PLA, PETG, ABS, ASA, TPU, PC, or PA) using the same nozzle.
Can you go over the process you use to switch back and forth between PLA and TPU filaments? What changes are you making on the printer and in the slicer? Maybe we can suss out where a problem might be introduced.
I’ve never tried TPU, but is it possible that some TPU is caught in the extruder, and when the PLA comes thru, it picked up some leftover TPU? I mean, doesn’t TPU melt at a higher temp then PLA? I don’t really know, just throwing out some ideas.
Sure and thanks!
I click unload on my laptop. Pull back the filament after it’s been cut. Raise the temp of the hotend and push though the new PLA filament. Click extrude a few times till the new filament comes out the hotend. Then I opened up this model from maker world:cable holder by Zivilist - MakerWorld and hit print. I got some very bad results which reminded me of the last time I swapped from TPU to PLA (as per the linked thread in the first message). So I printed the model from that first thread and got identical artefacts around the hole and the seam. Last time I got this issue (as detailed in the link) I power cycled, I unclogged it using the pin and a cold pull, recalibrated it and swapped the entire hotend - None of that made any difference. And each time I printed the model to check it looked identical. What ended up working was doing a full factory reset. So I have a method which will probably fix it, but I still don’t know the problem. And I don’t want to do a full factory reset each time I swap from TPU to PLA.
My best guess is somehow it keeps trying to print it as TPU despite me telling it to print as PLA? TBH I have no idea.
Looks like a partialy clogged nozzle or extruder to me. Try to do a “cold pull” if your having trouble after printing tpu. Tpu and other materials dont really mix well. Also be aware pieces of filament can break off in the extruder gears, which are right above the hot end. Ive had to take that thing apart a few times already, and some people have clear extruder gear covers so they can see into that area. Great idea that. If you’re going to take apart your extruder, first retract the filament using bambu or orca, then follow a tutorial on how to do it. WATCH OUT FOR THE FILAMENT SENSOR RIBBON CABLE. That thing tears incredibly easy. Ive broken two of them. its the tiny connector above your fan cable. Also make sure you turn your machine off first before you unconnect connectors so you dont short anything. tpu can get wet really easily, dry it in your printer overnight with the bed on if you dont have a dryer.
If I may say, if you’re looking for troubleshooting help, you need to slow down and address one item at a time. One thing is certain: performing a factory reset does nothing for filament and model settings. It only resets the printer’s internal configuration, affecting memory and network connectivity, nothing else. If a factory reset is affecting your output, it’s an indication that something is corrupted in the way the model is being sliced or uploaded to the printer.
Let’s first focus on what’s happening and get some facts:
If I had to guess, your settings are getting corrupted or reverting to a different filament profile. This happens to me when I’m not careful with loaded settings. In Bambu Studio, changing printer profiles can cause it to switch to an unrelated filament profile. I once had PETG loaded, but the profile reverted to PLA when I changed the printer profile, which was frustrating. 
Try closing Bambu Studio and reopening it after filament swaps. This is a less invasive debugging step than performing a factory reset and ensures that the project settings are always reset to the correct values. While it shouldn’t be necessary, it’s a diagnostic measure that may help.
With TPU, after filament swaps, I find it helpful to print a small test object. I usually print a 25.4x25.4x2mm cylinder primitive, which ensures a total purge of the filament path. If you’ve ever tried this with two contrasting filament colors, you’d be surprised at the amount of junk left in the nozzle that the purge didn’t expunge. Try this step to confirm your filament is fully purged between changes.
Disclaimer: I hate TPU—it’s the devil’s spawn of filament
. But it’s necessary for certain prints, so I’ve learned to “tame” it, not “master” it.
If you think your TPU filament is dry, you’re probably wrong 
. Dry it again. Even a 0.03% moisture content can be the difference between “stringy” and “gappy.” Always dry the filament before using it.
Turn on the setting “Avoid Crossing Walls.” While it might not make a difference in your example model, it can really help.
When dealing with a tricky model, a good fallback is to run in silent mode, which reduces all nozzle movements by 50%. If you’re motivated, you can manually adjust the speed settings to find the ideal flow rate, but silent mode offers an easy one-click option that cuts speed by 50% (though it doubles print time). The difference in print quality is significant.
Experiment with layer heights. A finer layer height like 0.08mm can help with some models. I’ve found that keeping the layer height below 0.24mm works best for most TPU prints. The photo above as an example, the one on the right was at 0.28 and the one on the left 0.08 at 50% speed. It was still string as ■■■■ but it got the job done.
Did I mention drying the filament?
Hi and thanks for the advice.
As I’ve said I have done cold pulls and even swapped the hotend and had the prints coming out exactly the same.
TPU tips
So First the issue is when swapping from TPU to PLA. But when using TPU I am following all threee tips already. But many thanks!
I think I agree with your idea about the printer profile or something. It seems like it’s trying to print TPU still even though I’ve checked 100 times that I’ve told it to print PLA! As said I’ve even got it to print right off the SD card.
Things that have not worked:
Things that have worked:
I’m going to try a factory reset and see if that fixes it again.
So you have not checked if your extruder gears are in some way gummed up or jammed? Its a very likely cause of your failures. Please post your solution when you find it, dont ghost the forum
So the factory reset has fixed the issue. Which on one hand is good. But on the other hand I don’t know what causes the problem. And it’s happended both times I’ve swapped from TPU to PLA. So I’d still like to figure out another solution or at least what the problem is…
Before Factory Reset (Just first layer):
The reason the factory reset “fixed” the model is that it reset the flow dynamics calibration you had for the filament.
The image of the first layer with the inside “pulled” away from the edge is a direct indication of an incorrect K value.
Here is the wiki for how to correctly calibrate your filament.
Hi Jon,
So I did flow dynamics calibration for my (SainSmart High Speed K=0.20) TPU filiment profile. But surely when I swap back to my PLA profile it should not carry over the calibration to that filiment? Or does it? How do I prevent this problem next time?
Thanks!
