Nozzle cleaning consistently failing with FLEX filament  

RE: Nozzle cleaning consistently failing with FLEX filament

I've yet to try TPU in my Core One (Bowdens and TPU aren't a great mix, sigh).  As for nozzle checks, and I'm guessing here, if its high temp TPU there is a Slicer setting for the filament preheat/idle temp; if the TPU isn't malleable during the cleaning, you might try raising the idle temp.

Hopefully someone who has been successful printing TPU/FLEX can provide better info. 

RE: Nozzle cleaning consistently failing with FLEX filament

I don't have any difficulties at all threading 95A TPU through the Bowden tube and through the filament sensor. For the softer TPU, you'll have to remove to Bowden tube and feed it directly into the extruder, then the next problem is getting past the filament sensor. I saw a mod on printables to replace the filament sensor spring with small magnets which allows easier insertion.

RE: Nozzle cleaning consistently failing with FLEX filament

Arrgg... editing seems to be broken. What I wanted to add, for the nozzle cleaning problem, the forum consensus is that EMF from the PWM signal to the heater element is inferring with load cell readings which causes this problem. The work-around that people have found successful (including me) is to turn off the heater prior to doing the nozzle cleaning set. In the Start G-code section would add the following:

M84 E ; turn off E motor

;
; Added - turn off temperature
;
M104 S0

G29 P9 X208 Y-2.5 W32 H4

RE: Nozzle cleaning consistently failing with FLEX filament

Wow!  That actually worked - THANKS!!!  However, that kind of begs the question - Why does it succeed with other filaments?  I have successfully printed with PETG, ABS, PLA and PCTG so far.  Only TPU gave me problems with nozzle cleaning.

RE: Nozzle cleaning consistently failing with FLEX filament

Posted by: @frank-8

Wow!  That actually worked - THANKS!!!  However, that kind of begs the question - Why does it succeed with other filaments?  I have successfully printed with PETG, ABS, PLA and PCTG so far.  Only TPU gave me problems with nozzle cleaning.

Not really sure other than to think (guess) that since TPU is "squishier" that it's harder to get an accurate load cell reading? Anyway, I had this problem with PETG as well so I leave it in. Alternatively for nozzle wiping you can use this method instead (which is better): Prusa CORE One Nozzle Wiper 

RE: Nozzle cleaning consistently failing with FLEX filament

Last night I was getting nozzle clean failures again with TPU, so I followed an earlier suggestion and reversed the build sheet on the plate (exposing an unused corner for the nozzle clean step) and this allowed the nozzle clean to succeed.  Then I inspected the original front right corner and discovered I had some TPU residue there, which undoubtedly caused the original failure. So I guess this bolsters the 'too squishy for the load cell' theory.

I've also ordered the parts for the Prusa Core ONE Nozzle Wiper mod - and we'll see how this goes.  What I don't quite understand is why Prusa insists on the nozzle clean step, even though there is plenty of evidence that it is a) unnecessary in most cases, b) unreliable with FLEX filaments (and apparently others as well) and c) pissing off loyal Prusa customers.

RE: Nozzle cleaning consistently failing with FLEX filament

Posted by: @hyiger

Arrgg... editing seems to be broken. What I wanted to add, for the nozzle cleaning problem, the forum consensus is that EMF from the PWM signal to the heater element is inferring with load cell readings which causes this problem. The work-around that people have found successful (including me) is to turn off the heater prior to doing the nozzle cleaning set. In the Start G-code section would add the following:

M84 E ; turn off E motor

;
; Added - turn off temperature
;
M104 S0

G29 P9 X208 Y-2.5 W32 H4

is there a reason that you wrote the line of code with the extra ;'s and the comment above the command instead of after like the rest of the G-code. 

basically, I'm trying to figure out, why not write it as 

M84 E ; turn off E motor

M104 S0 ; turn off temperature (user added)

G29 P9 X208 Y-2.5 W32 H4

my only thought was you wanted it to stand out, so I added the (user added).  if there is something else with the PrusaSlicer that requires user edits be completed that way please let me know. I have edited G-codes in the past but never withing Prusa or any 3D printing. 

Posted by: @frank-8

Wow!  That actually worked - THANKS!!!  However, that kind of begs the question - Why does it succeed with other filaments?  I have successfully printed with PETG, ABS, PLA and PCTG so far.  Only TPU gave me problems with nozzle cleaning.

alternatively, you can also lower the idle temperature of the filament. I was having similar issues and found that helped. it's basically the same fix of making sure the material isn't oozing. I also found that putting a strip of masking tape where the printer does the nozzle cleaning helped. 

RE:

How something is commented is usually personal preference - preceding code with comments is standard practice in larger code projects as comments within functional code is discouraged and often not allowed. Preceding also gives you more room to write complex notes. But gcode is generally single line, thus inline comments on simple commands works well enough.

https://en.wikipedia.org/wiki/G-code

https://marlinfw.org/meta/gcode/

RE: Nozzle cleaning consistently failing with FLEX filament

The comment style is just the way I like to do it, makes it easy for me to find my changes. Where you put the comment, how it's formatted (or you can just leave it off) is up to you.

RE:

I've also had a hard time getting TPU to pass nozzle cleaning/bed probing recently with my garolite bed.  I noticed that TPU doesn't do the retract process after loading or printing like the non-flexible filaments do.  This is a firmware matter, and I suspect they excluded TPU from their recent retraction code because it must lead to other problems.  The other materials have been operating well for me since they added the retraction. Previously with the Mk4S (before conversion) I'd been able to reliably pass these stages with TPU by dropping the nozzle temp, as noted above.  I haven't spent much time yet trying to solve this, and will likely keep dropping the nozzle temp further before giving up.  

I also *just* installed a nozzle wiper, which should help with the other filaments that use the retraction code, but I don't expect it will help with TPU because if the nozzle is still hot it continues to ooze after wiping.

-J

RE: Nozzle cleaning consistently failing with FLEX filament

I Just installed the nozzle wiper myself, but although I tested it using the test script described in the 'maker' notes for the scrubber, I haven't actually printed anything with it yet.  I have attached my test print file; simply copy this to your Prusa USB stick, then select and 'print' it using the normal print file selection menu.

M17 ; enable steppers
G28 ; home all without mesh bed level
G0 X210 Y-14 Z2.0 F3000;
G0 X168 Y-16 Z1.5 F3000;
G0 X168 Y-14 Z1.5 F3000;
G0 X210 Y-16 Z1.5 F3000;
G0 X168 Y-14 Z1.5 F3000;
G0 X168 Y-16 Z1.5 F3000;
G0 X210 Y-14 Z1.5 F3000;
G0 X210 Y-14 Z1.5 F3000;
G0 X168 Y-16 Z1.5 F3000;
G0 X168 Y-14 Z1.5 F3000;
G0 X210 Y-18 Z1.5 F3000;
G0 X168 Y-16 Z1.5 F3000;
G0 X168 Y-16 Z1.5 F3000;
G0 X210 Y-14 Z2.0 F3000;

RE:

Posted by: @frank-8

I Just installed the nozzle wiper myself, but although I tested it using the test script described in the 'maker' notes for the scrubber, I haven't actually printed anything with it yet.  I have attached my test print file; simply copy this to your Prusa USB stick, then select and 'print' it using the normal print file selection menu.

Before running this, I would advise to manually checking the coordinates first. X and Y should be fine but the Z axis will most likely need to be adjusted. For reference this nozzle wiper is here: Prusa CORE One Nozzle Wiper

RE: Nozzle cleaning consistently failing with FLEX filament

I also used the one linked just above.  It uses a minimum of material, sits beautifully on the folded lip under the heat bed, and keeps all of your activity on the right side of the bed where the rest of the pre-print activity is done.  I essentially used his m3 nut version, and it is very solid.  The gcode appears to wipe properly at a reasonable height. I don't have many prints on it yet though, so I may adjust in the future.

-J