MK4 and Flex (TPU)  

RE: MK4 and Flex (TPU)

Almost a bit boring ......The MK4 has been working well so far. Even with TPU 95 without any problems and relatively fast.

RE: MK4 and Flex (TPU)

I tried to print TPU with my Mk4. 
95A. 

But I already had problems with loading the filament. It was so wobbly that the gears of the extruder couldn't grip it properly and hardly anything came out of the nozzle.

Any advice??

RE: MK4 and Flex (TPU)

Avoid sudden changes in your printing speed. Best set all the speeds to the same value. TPU parts tend to be smallish, so speed concerns should not be such a big issue. See screenshot, these settings/changes worked for me on the SainSmart TPU profile that comes with PrusaSlicer.

RE:

Mk4 here, input shaper installed and great results with PLA in terms of quality amd print times almost half! But 1st time I tried TPU (TPU LITE) I had problems and during 1st layer clicking sound inside the nextruder, I stop the print and I normally find enrolled filament in the gears.

I set 220° and tried with 0.5, 1, 1.5mm reyraction, same result.

I set all printing speees at 50mm/s and also at 30mm/s, same result.

Dumb question: is my error maybe having created the TPU profile starting by wrong Prusa (PLA) filament preset? Which could it be a typical preset to start from ? Filotech TPU..?

Thank you all!

RE: MK4 and Flex (TPU)

It is best to start from a flex profile.Pay particular attention to the maximum flow rate. This is 15mm/s² for Pla and 3.5mm/s² for Flex.

RE: MK4 and Flex (TPU)

I then started from A95 profile, my case filament is TPU LIGHT A94, and results were excellent indeed!

Thanks

RE: MK4 and Flex (TPU)

If you want more speed you can slowly increase the max flow rate until you have problems. Then back off a little. Maybe also increase the temperature a bit when you increase the flow rate.

Max volumetric speed

RE: MK4 and Flex (TPU)

I printed some ninjaflex the first day after I upgrade my first MK3S to MK4.  it worked flawlessly.  Start with something the Ninjaflex or Semiflex profiles and for me it was basically setting the temp a bit higher, 246.   it worked great first time for me.  This was always iffy on the MK3.  I definitely like what they've done with the MK4.

RE: MK4 and Flex (TPU)

Today I tried again to print TPU (TPU LITE SHORE A94), same settigs used before couple of weeks ago (see post above) with no isseus at all, after 1 min clicking sound and no way to drive filament into MK4 nextruder. No probs with PLA and LW-PLA... I really don't understand reasons. 

TPU dry and kept in vacuum bag, no issues there. 

Filament loaded with no probs and some difficulty to unload due to jam in the nextruder.

I even tried to reduce all print speeds to 25mm/s, no improvements.

MVF set to 2.5, or even less : same story.

Few  shots attached of print, filament and printer settings used in last tests...

Thanks in advance for any suggestion 🙂

RE: MK4 and Flex (TPU)

P.S. It seems that only way I can print TPU today is using MVS of 1.0 (used to be 2.5 or 3) and all speeds to 30mm/s (used to be 50mm/s). Temps about 230°C.

Now, could all this have anything to do with printing temps? I mean, maybe increasing temp to 240°C and see if MVS = 2/2.5 is achieveable will have any sense?

Thanks again for any suggestion 🙂 

RE: MK4 and Flex (TPU)

I print TPU 95 with 4.5.

But some seem to have problems. There is one solution that I would try first if I were you.

Increasing the temperature also helps within certain limits.

RE: MK4 and Flex (TPU)

This solved my problem! I recommend it to everyone having issues with TPU!

Posted by: @rainer-2

I print TPU 95 with 4.5.

But some seem to have problems. There is one solution that I would try first if I were you.

Increasing the temperature also helps within certain limits.

RE: MK4 and Flex (TPU)

Very interesting indeed! I'll print it...

RE: MK4 and Flex (TPU)

All tpu is not created equal.   With sainsmart TPU(92A)  it prints flawlessly with the default sainsmart tpu profile.  Ninjaflex(85A).... not so much.  I've spent a couple days really refining it.   I'm pretty close on it now.

For me I get SEVERE under extrusion with the default 238 print temp.  I have to do 246.  and the default 1.12 extrusion multiplier, I need at 1.21.  MVS is set at 3.2.  and the max print speed, set to 10mm/s.  This is all very different than when these printers were MK3S+.   But different drive gears, etc, I get it.   it's just interesting that the stock ninjaflex profile is so far off from what it takes to get it to print well.

RE: MK4 and Flex (TPU)

Is there an easy way to remove the old idler lever and and install the new Nextruder Modified Idler Lever?

RE: MK4 and Flex (TPU)

So for my one printer it ended up that the nozzle was loose in the heat block and it's why I had to increase temp.  Once I fixed that and adjusted the idler tension to be more than it was, ninjaflex tpu prints ok in both printers at the the stock temp.  I didn't modify the any idler lever though.   As far as replacing idler level, I don't think there' any way around taking the PG box off there which is why I'm inclined not to do it.  Plus I have print it in ABS to match my other parts and I can only do that when I can open window and ventilate.  I only have issues with printing things like lettering where there's basically no infill, just perimeters.   I'd be interested to hear if anyone else has tried the modified lever and has had good results.

RE: MK4 and Flex (TPU)

It takes maybe 5 minutes and 2 screws. Should be no problem at all. 

RE: MK4 and Flex (TPU)

I installed the new Idler arm and it works great. 

RE: MK4 and Flex (TPU)

Be sure to calibrate the transmission after replacing the tension lever arm and mounting.