I’m looking for help diagnosing an X1 Carbon that consistently produces stringing, blobs and slight overhang curling when printing TPU. I have another X1 Carbon running the exact same print profile and it produces perfect results, so I have a direct comparison.
Symptoms
Heavy stringing and random blobs.
Slight upward curling on overhangs.
Prints much better in Silent Mode (50%)
Lowering nozzle temperature made the print quality even worse.
What has already been replaced
Complete hotend assembly.
TH (toolhead) board.
Front cover / part cooling fan assembly.
None of these replacements changed the issue.
What has been checked
Same firmware on both printers.
Same nozzle size.
Same G-code and slicer profile.
Different TPU spools.
Different filament dryers (including a new dryer).
Extruder gears inspected and cleaned (looked pristine).
Additional observations
One printer prints the exact same model perfectly while this printer does not.
I previously noticed a connector on the original TH board that felt looser than on the good printer, but replacing the TH board made no difference.
I printed a mod fan duct for the hotend cooling fan. No difference.
I recently discovered that one of the cable chain/toolhead support links at the top of the toolhead had become disconnected. I snapped it back into place but have no difference in result after.
At one point the toolhead was accidentally powered on while detached and hanging from the cable harness, so I am wondering whether the wiring harness could have been damaged internally. No visible clues.
At this point, are there any known X1 Carbon issues that could cause these symptoms despite replacing the hotend, TH board? Has anyone experienced a faulty wiring harness, mainboard, or another less obvious cause that resulted in similar TPU print quality problems?
I have trouble shooted with the assistance of an AI agent and last suggested probable cause was the extruder motor running to hot. Any DIY fix to this? Any way to investigate?
Any suggestions or similar experiences would be greatly appreciated. Thank you.
it seem you have replaced quite a lot of unrelate parts. Since tpu is softer than other filament,you should first check whether the printer prints normally with other materials.
If other materials work fine, the problem most likely lies with the filament.
Stringing is usually caused by excessive moisture inside the filament.Try drying your filament.
One more thing,this issue could also be caused by a loose screw on the back of the hotend heating assembly. try tightening it.
Instead of replacing parts, I would instead be swapping relevant parts between the two printers. Start with the hotends.
Also, ensure your PTFE feed path is as smooth as possible from the spool to the extruder. I typically unhook the PTFE right at the extruder and then manually push filament through the feed path, it helps me identify specific areas of resistance. Do that with the TPU and see if it’s getting hung up somewhere on the problem machine.
Finally, please share details of how you’re feeding the TPU. It’s notoriously fickle. Pictures would be best. I like the idea of running tests with easier materials.
I’ve only printed about 2 rolls of TPU for AMS with my X1C (around 2500 hours) and have yet to encounter stringing, I’ve never done a cold pull either. However, I am very religious in drying of the TPU, and I even sometimes dry the TPU as it’s being fed to the printer. When I print as I dry the filament, I lower the nozzle temp 5-10 degrees just in case. I may just be very lucky.
Before I started printing TPU, I took a lot of tips from the below guide, it’s a good read for TPU printing if you haven’t read it yet. This, of course, doesn’t eliminate a issue you may have with the printer itself.
My dryers are set up elevated to the left with a direct and straight line to the back ptfe tube. The drag should be very very minimal. As mentioned before I even swapped the dryer with the good printer. So any drag or resistance from the dryer must be ruled out.
I will be sure to test with different filament as soon as the slow TPU print is finished.
What would it tell me if there’s an issue here too?
Extruder gear? Motor?
Extra content. When printing at 100 % speed the item prints perfect with clean surfaces and no visible under extrusion. It is only within the crevasse/hole down the vertical middle, where the stringing occurs.
I would say it’s over extrusion or too much heat, what’s the room temp where your printer is? Have you tried lowering the hotend temp by 5-10 degrees on test prints?
I’ll ask a question that might seem obvious, but which is still important:
After all the swapping back and forth, was the printer reset to its factory settings and recalibrated?
Not doing so could significantly hinder your troubleshooting efforts, as you won’t have a clean start after replacing all those parts. You never know what old sensor data the printer might still have stored, even after replacing many parts.
Keep in mind that even if you have two identical printers and the same g-code, you don’t know how the printers’ internal calibrations differ.
What I would personally do next might be considered unnecessary, but it would help to narrow down the problem further: I would do a test print to check for stringing, using PLA and a standard profile. Yes, PLA. Just to check whether the printer fundamentally has a stringing problem or really exclusively at TPU.
This information alone would help you narrow down the problem significantly, and a test print with PLA takes no more than ~15 minutes anyway.
First time hearing of this option. I have thought about doing the old shut off turn on option, by just resetting. I have very little technical knowledge and when we first aquired these printers I wasn’t the one unpacking and getting them started. So I have been hesitant to do such a procedure. You’re telling me if I reset and do the calibration through the touch screen, it won’t alter the machine from any critical settings my previous associates made to get it going?
There are probably only two possible answers to that, since I don’t know your situation:
Ask the person who set this up for you
…or learn how to set it up yourself - it’s not that much of a deal
That said, just to put your mind at ease: A factory reset cannot damage your printer - it’s simply the same state as when it was delivered to you. One of the most common challenges is that you’ll need your Wi-Fi login and password. That could be a roadblock for you; I don’t know the circumstances.
Since you missed it the first time, the only “critical settings” your crewmates input into the device is 1) your region 2) your wifi connection info 3) select yes or no to do the calibration
