TPU/FLEX Extruder cracks my filament (Polymaker)
Hello prusa-folks,
my MK4 dont want to print TPU. First i tested the Amazon TPU. The filament always stucks in the extruder. After some tweaks in the slicer i decided to test another brand. My way to go is normally polymaker so i bought a roll of that filament "Polymaker PolyFlex TPU-95A -Black". In the end the same result. In the prusaslicer i startet with the given settings of polymaker. I turned some of them down like print speed or retraction...but always the same. The extruder pulls the filament apart. Sometimes the printer didnt start even the print and the filament is broken and other times the printer yells for filamentchange becouse the filament is broken. Both rolls of filament are dry. I adjust the extruderscrews several times. In the photo i made the screw are more stiff. In other cases they are really loose...but same result. I tried with fan on and off...no change. The printer sits in a housing and the nozzle is 0,4mm.
So now some settings of my prusaslicer:
- Layer height: 0,1
- vert. shells: 3
- hor. shells: top&bot: 4
- infill 20%
- speed (all settings): 20mm/s
- nozzle temp first layer: 230°C
- nozzle temp other layer: 225°C
- bed: 45°C
- Extrusion multiplier: 1,1
- Fan: first 3 layer off after them 25%
- MVS: 1,3mm^3/s
- z lift: 0mm
- retraction lenght: 1mm
- retraction speed 20mm/s
- deretraction speed 20mm/s
- minimum travel after retraction 2mm
The whole slicer settings for this filament will be in this post. (PrusaClicer_config_bundle)
I hope you can help me 🙂
Greetings and happy new year!
RE: TPU/FLEX Extruder cracks my filament (Polymaker)
hmmm no ideas?
RE: TPU/FLEX Extruder cracks my filament (Polymaker)
Have you backed off the tension screw idler. polymaker tpu works fine for me.
i3 Mk3 [aug 2018] upgrade>>> i3MK3/S+[Dec 2023]
RE: TPU/FLEX Extruder cracks my filament (Polymaker)
Hi, yes i loosen the tension screws....no change in this. Which slicer do you use? Could you post your settings for polymaker tpu? Whicht shore has your tpu?
RE: TPU/FLEX Extruder cracks my filament (Polymaker)
I had some trouble with soft TPU on my MK4 that I have now (fingers crossed!) solved.
First problem was that the filament sensor would intermittently report that there was no filament. Presumably the soft TPU (Recreus 82A) was being flexed by the sensor. I first started to print with the filament sensor disabled (a menu item on the printer screen, but I don't remember exactly where). That was better.
Then I had problems with unloading the filament. It would always go behind the Nextruder gear and get stuck. I assumed that the filament sensor was preventing the filament from freely moving back out of the extruder and so removed the small spring and ball bearing to give a free path. Better, maybe. In the end I realised that the slicer settings of speeds for unloading in my custom filament profile were set to defaults that were way too fast. (I had made the profile before I got the MK4, and before PrusaSlicer had settings for those things.) I now have the 'Unloading speed at start' set to 40 and 'Unloading speed' set to 35. That made quite a lot of difference, but I still needed to put some tension onto the filament to get reliable unloading.
The last fix is a good one. I now have a modified Nextruder main plate installed ( https://www.printables.com/model/599472-modified-nextruder-main-plate). It has a plate that prevents filament from getting behind the Nextruder gear. (It is possible that the improvement I saw after installing this part was due to my print of it (in ABS) having a finer layer height and superior quality to the original Prusa part, but I think that the superior design of the part is the cause.)
Now I am able to reliably deal with soft TPU.
RE: TPU/FLEX Extruder cracks my filament (Polymaker)
I will try some of that. But did you had the problem that the filament always breaks of like in this picture?
RE: TPU/FLEX Extruder cracks my filament (Polymaker)
No, I've never had the TPU break in the extruder unless I've pulled to hard trying to undo a tangle.
Sorry, I missed the topic a bit in my response. I did not understand what the photo was showing, but now that I've translated "wechselnd" I am assuming that you've run the filament unload routine. When you say that the extruder pulls the filament apart, do you mean during printing, or during unloading? If the stuff is getting stuck in the hotend or the metal tube then the unload routine might pull it apart. For that circumstance I would recommend a cold-pull with some nylon filament (or special cleaner filament) to clean the insides and allow the filament to come back from the nozzle easily.