TPU flex filament slipping during Auto Load

[florbela]

Hello

this is a follow up to the topic:
viewtopic.php?f=17&t=2040

So, I have installed the part needed to use flexible filaments without any issues.

First time I did the auto-load of the TPU flex, there were no problems, the filament reached the nozzle and I started printing a small disc.
However, at half way throught the printing, during a retraction movement the filament got worn, the driving wheel was rotating but the filament didn't move at all. I had to cancel the print and do the Auto Unload. After this,I couldn't do the Auto Load properly. Everytime I tried, the filament got worn as seen in the picture. I observed that, during the Auto Load, the driving wheel rotates at 2 different speeds, firstly rotates very slowly and then quicker. At the beginning, when the rotation speed is lower, the filament goes through with any problem at all, however, when it rotates quicker, it's when the filament gets worn.
Did anyone else had this issue? Is there any suggestions to solve this?

Thank you very much!

[DomingosRodrigues]

Hello Florbela,

My bad I did not give you the whole information on the previous post.

The TPU filament due to its flexibility should be manually loaded and then extruded using the manual extrusion option (at PETG temp). Auto load can grind the filament deppending on the brand of TPU.

What profile are you using to print with TPU?

Best regards

[florbela]

Hello Domingos

I am using the B2X300_TPU_TPU_v1.2 profile.
I started to use the manual extrusion and eliminated the problem with the autoload
However, during printing it happens again. I have disabled the retraction, have slow speeds for printing and travel (12 mm/s and 60 mm/s respectively) and that is still hapenning at some point during the print. May be I have to reduce even more the speed? At the moment I am trying to print only a small disc 16 mm diam with 6 height just to optimize the printing conditions.
I don't know if it is related, but, sometimes I am getting few bobbles when the filament is being extruded. Do you think that it is because of the moisture? Should I dry the filament before using it?

Many thanks

[florbela]

I have not change the material type though, as shown in the picture. Does that have any influence on the gcode or is it just a guidance for colors etc?

[DomingosRodrigues]

Hello Florbela,

That is the correct profile for TPU. You should not change the filament type in cura a our profiles already include all the needed information.

What brand of TPU are you using?

If there is bubling during the print usually it means one of two things, either the filament has absorved a lot of moisture and needs to be dried or the temperature is too high for your print speed/material combo, and the filament is degrading inside the extruder possibly causing the problems with extrusion that you mentioned.

With TPU usually a slow speed of arround 10mm/s print (you need to change the other values in cura otherwise the print speed does not override infill speed, top bottom speed, etc. And the travel as fast as the printer can achieve, for the B2X300 120 is a good value but you can go up to 200-250 without issues if your printer assembly is very good and the axis move quite freely with no binding.

Also when using TPU some brands require you to disable the B2X300 bowden tube compensation, as it makes very abrupt movements that can grind the filament to compensate the springiness of the bowden tube, by commenting (adding a ; at the begining of the line) the start gcode line: "M900 K180 ; K-Factor PLA"

Best regards
Domingos Rodrigues

[DomingosRodrigues]

Hello Florbela,

One more idea that might help you with this issue, you should perform a Cold pull to clean the printers nozzle prior to using TPU as it is very sensitive to mixing with other materials and can cause both the extrusion issues you have and the bubling you mentioned.

The "Cold pull" procedure can be found inside "Maintenance" on the printers LCD, all the steps are explained on the LCD.

Best regards
Domingos Rodrigues

[florbela]

Hello Domingos,

sorry not replying sooner, I was doing some other projects in the meanwhile.
Just to clarify, to disable to bowden tube compensation, I should add an ";" in the beginning of the line "M900 K180 ; K-Factor PLA" so it would be ";M900 K180 ; K-Factor PLA", is that right? Many thanks and Merry Christmas

[DomingosRodrigues]

Hello Florbela,

No wories .

Yes that is it.

Best regards
Domingos Rodrigues

[florbela]

Hello Domingos

Happy new year!
I just wanted to share the result of printing with TPU flex.
I changed the speed settings and add that ";" to the gcode file and voilá, it worked
It had a littler bit of under-extrusion, but that's easy to solve.

Many thanks for your help!