Experience MK4 with MMU3
Disclaimer: this is not done with any official release from Prusa. I made my own cable from the MMU3 to MK4 (s. separate threat). My first test was running good (with PLA and PETG). Now I was trying a more advanced model (molded cube).
1100 tool changes; 150um speed profile; printing time more than 1 day.
Result:
Not bad - but far from perfect.
Some underextrusion - the speed profile might create some problems due to the additional friction of the MMU. Slower print and a bit of overextrusion might help.
Further observations:
Some missing layers. The filament was detected but did not make the way into the nozzle. The MK3 is detecting those failures (observation of the extruder stepper current??). A SW-Update might fix this.
The filament tips where just fine and created no problems with the MMU and or loading into the MK4. But after the print there where quite a lot of debries in the gear:
During the print I experience quite a lot of "unload errors". The filament sensor of the MK4 did got stuck and was only possible with quite a lot of trial and error (pushing filament in and out until the reading was OK). There was no way to clean the sensor nor to recalibrate during the print.
Again: this is an unofficial test and the final solution for prusa will address those issues. I think that the mainplate of the extruder will see a redesign and there will be some SW-updates addressing filament tips (cold pull strategy) and sensor problems (stuck sensor).
RE:
Another test, now with PrusaSlicer 2.7.3; MK4 FW 6.0.0 and MMU3 FW 3.0.3. In the first all mechanical parts where MK4 original.
First: the new ramming is a big game changer! The tips are more or less as cutted with a knife; no stringing.
In my last test (s. above) i was experiencing 3 problems:
- filament sensor stuck
- not correct loaded filament (sensor was triggered, but filament was not loaded into nozzle)
- high amount of debris.
With the new firmware a not correct loaded filament is detected. The MMU3 tries 3 times to reload, then you need to interact. This happened surprisingly a lot of times. But everytime I was cutting the tip with an angle, the load was without trouble. This leaded me to the assumption, that a perfect flat tip is creating another problem: the filament is not guided into the nozzle but stops at the edge.
I did a analysis of the main-plate-R2 and found, that the diameter of the lower filament guide was larger than the diameter of the nozzle entry. Therefore, by mechanical missalignment or tolerances, the filement could not enter the nozzle.
I did a small redesign of the main-plate-R2 an implemented a small funnel, so that the output diameter is now 2mm whereas the nozzle diameter is 2,5mm. By this measure the filament was guided 100% of the time into the nozzle. And as a side effect there were no debris in the nextruder!
I think the remodeled part from Prusa will just do the same.
I printed the part with PETG, 0,05 layer thickness. The whole needed a bit of rework (2mm drill of a round file will do it).
My modiefied main-plate:
The question will be how long the part can print (PETG) or if I have to order the spare part from Prusa.
Result with 480 tool changes without any interaction:
For now I'm sattisfied. Next test will be with supporting material.
RE:
the stl for the changed main-plate
RE: Experience MK4 with MMU3
the upload did not work - another try:
RE:
Very nice design !
I am going to try and print it in poly carbonate
Thanks
RE: Experience MK4 with MMU3
Perfect in PC Blend !
