First print on the MMU3 with MK3.5 board and REVO: a disaster!
Hello,
today I finally tested the MMU3 after I have upgrade the MK3S+ to MK3.5. I must say that during the upgrade I had to rollback from the new REVO 60W to the old REVO 40W, since the REVO 60W is not (yet ?) supported by the FW 6.0.0 while it was on the MK3s board. So now the old REVO 40W is installed on the printer. After that the basic calibrations and setup wizard ended correctly, I started to test the MMU3 with the new board.
After the basic calibrations I started a 4 colours print on PLA using Prusament PLA (that should have its tuned profile). The first thing I noticed were the abnormal strings it was doing when retracting the filament. I did not had them when it was a MK3S+ REVO. I had to cut constantly the strings to avoid mess in the MMU3.
You can see here the aspect:
However around 75% of the print I started to hear strange creaks from the extruder, and at filament extraction the process completely failed. Any RETRY was unsuccessful.
NOTE FOR PRUSA: The RETRY button and a QRCODE on the LCD is not useful at all. It lacks some basic options like SUSPEND the print or ABORT the print. A SUSPEND option would allow to save in memory the gcode line, and resume in a second time when the MMU/Nozzle is fixed, since the print is in a status where it can be resumed later. Of course SUSPEND SHOULD NOT turn off the plate, otherwise the print will detach...😎
Why the filament did not retract ? Because it clogged into the REVO. No way to remove. This is the second time it happened to me.
So, since I did not have such other options other that press the RESET BUTTON, I reset the printer.
Now I need to:
- cut the filament before entering the MMU3
- dismount the MMU3 PTFE tube to the extruder
- remove the screw and spring from the extruder
- remove the filament from the MMU3 device, I can see there the filament almost cutted by the MMU3 gear
- Cut it just above the PTFE tube
- Screw the REVO nozzle, and remove it.
- Heath it with a Hot Air gun at 170° and manually remove the filament
- Reinstall all. 😓
NEXT STEPS:
Analyse what values are in PrusaSlicer for the MMU3. I had a good setting that I calculated, but it was erased when I upgraded. I should rebuild it. May be the ramming values are not optimal for the REVO 6. If you see the photo, the filament have the exact shape of the internal end of the REVO nozzle: this could mean that it is too down.
Moreover, the fact it clogged twice, means that the extruder fan speed could not be optimal or insufficient to cool properly the power of the Revo.
May be even a new powerful fan could be required.
Regards
RE: First print on the MMU3 with MK3.5 board and REVO: a disaster!
Yes I had longish filament strings with my REVO MMU3/V3.5 as well with my eSun filament compared to what I had in the Mk3S MMU environment.
I did increase the number of cooling moves (from 1 to 2) which seemed to help but there is still some stringing which the MMU cutter is cleaning up. I also slowed down all the print speeds back closer to the Mk3S environment which the Revo won't have as much thermal inertia for the unload sequence (ie the filament will be cooler). I, like you, do want to get back to looking at parking position etc when I get the chance.
I am having a bigger problem though with the MMU/3.5 grinding little divots on the filament when loading during a Tool change, (at the end when the Filament sensor triggers the extruder motor stops but the MMU feed pulley has a slight delay before it stops hence a grind), so I have adjusted the MMU tension screws even less than the Prusa recommended to minimise it. It also causes a lot of detritus in the MMU which can get into the PTFE tubes.
I have a theory that on rare occasions these little divots can line up with the extruder hob gear which can then lead to further grind and a missing layer on the print (I haven't been able to directly observe this occurrence yet on the 24hr+ prints it typically occurs on). There seems to be a lot more filament waste build up in the extruder than before as well.
RE: First print on the MMU3 with MK3.5 board and REVO: a disaster!
Hi, I got also the same issue. My 1st filament was completely ground on the MMU3.
Looking at the issue I noticed that for a strange reason, the force to apply to the filament to extract it from the spool needed to be extreme. 😲
I have all my filaments inside cereal boxes with desiccant, always travelling inside PTFE tubes. I think that some time the filament twists and kinks through the long path through PTFE tubes to the buffer and then to MMU3, and due to that, it requires a strong torque to move it. In some cases the force required is so great that the physical structure of the filament gives way and crumbles. I will setup a dynamometer measure to test what happen (when happens).
Probably I will need to review all the PTFE tubes lengths and shorted them.
Posted by: @bazzalight
Yes I had longish filament strings with my REVO MMU3/V3.5 as well with my eSun filament compared to what I had in the Mk3S MMU environment.
I did increase the number of cooling moves (from 1 to 2) which seemed to help but there is still some stringing which the MMU cutter is cleaning up. I also slowed down all the print speeds back closer to the Mk3S environment which the Revo won't have as much thermal inertia for the unload sequence (ie the filament will be cooler). I, like you, do want to get back to looking at parking position etc when I get the chance.
I am having a bigger problem though with the MMU/3.5 grinding little divots on the filament when loading during a Tool change, (at the end when the Filament sensor triggers the extruder motor stops but the MMU feed pulley has a slight delay before it stops hence a grind), so I have adjusted the MMU tension screws even less than the Prusa recommended to minimise it. It also causes a lot of detritus in the MMU which can get into the PTFE tubes.
I have a theory that on rare occasions these little divots can line up with the extruder hob gear which can then lead to further grind and a missing layer on the print (I haven't been able to directly observe this occurrence yet on the 24hr+ prints it typically occurs on). There seems to be a lot more filament waste build up in the extruder than before as well.