Is the MMU2 finally starting to come together?  

Re: Is the MMU2 finally starting to come together?

Just to confirm, 4mm OD 2.5mm ID? This seems like it'll solve a lot of issues, so I'd like to look into this.

Did you chamfer the inside to 4mm, or just leave it as 2.5mm throughout?

Yes, 4mm x 2.5mm. I purchased 5 metres of transparent so that I could see the movement. The upper end is transparent.

I have attached my extruder body fix which removes the optical sensor (which is just not needed at all) and allows the Bowden to be a push fit into the body. I have more than 150 hours of print without the PTFE coming out, so I think it works OK.

Basically this stuff then? https://www.ebay.de/itm/Ptfe-Teflon-Rohrleitung-Rohr-4mm-Od-X-2-5-mm-Id-pro-Meter/131229025205?hash=item1e8ddc03b5:g:8koAAOxydB1Sfxo-:rk:4:pf:0

That's it.

Peter

Hi Peter. Did you replace ALL tubing for the MMU with the 2.5mm? I just got a 10m pack, so I'm looking to swap soon.

Re: Is the MMU2 finally starting to come together?

Hi Peter. Did you replace ALL tubing for the MMU with the 2.5mm? I just got a 10m pack, so I'm looking to swap soon.

No. Just the Bowden and the feeds from the spools to MMU. The short sections in the MMU are the original ones and I have removed the PTFE at the top of the extruder with my amended extruder body - which also works without the lower Festo.

I think that getting rid of the lower Festo and small PTFE at the top of the extruder, along with the optical filament sensor was the best solution for me.

Peter

Re: Is the MMU2 finally starting to come together?

[...] I have removed the PTFE at the top of the extruder with my amended extruder body - which also works without the lower Festo.

I think that getting rid of the lower Festo and small PTFE at the top of the extruder, along with the optical filament sensor was the best solution for me.

Peter

I'm finally getting around to printing the extruder body. It looks like you are using the same filament sensor cover as the MMU2, just without the festo? (e.g. pushing the PTFE straight into the extruder body). Could you confirm and/or snap a picture?

Printing everything out in my printer's green, including an adjusted idler without the filament sensor cleanup hole in it.. Hopefully it'll work out well. I'm having some extruder motor heat issues (unrelated, I think?) which are causing my prints to fail, so it's taken me a bit to start this printing..

If I can't get it printing, you might see me ask for more help in a different thread (for the heat creep through the extruder motor).

EDIT: I found Brian's passthrough coupling. I had forgotten about that. Going to be printing that now and trying it out. Currently, I just have the PTFE stuck into the extruder body, and that isn't working out too well for me (go figure).

Re: Is the MMU2 finally starting to come together?

I'm finally getting around to printing the extruder body. It looks like you are using the same filament sensor cover as the MMU2, just without the festo? (e.g. pushing the PTFE straight into the extruder body). Could you confirm and/or snap a picture?

I am not using a sensor cover; it's not required. The extruder body has grips inside it which hold the PTFE in place.

Printing everything out in my printer's green, including an adjusted idler without the filament sensor cleanup hole in it.. Hopefully it'll work out well. I'm having some extruder motor heat issues (unrelated, I think?) which are causing my prints to fail, so it's taken me a bit to start this printing..

There is a solution to over-heating extruder; reduce the "holding current". However this feature was removed in firmware 3.5 🙁 and now holding current is set to the same value as printing current, and this will contribute to hotter E motor.

EDIT: I found Brian's passthrough coupling. I had forgotten about that. Going to be printing that now and trying it out. Currently, I just have the PTFE stuck into the extruder body, and that isn't working out too well for me (go figure).

My PTFE just hasn't moved with 200+ hours of printing. But mine is cheap Chinese stuff which is quite hard - although it has 2.5mm ID.

The passthrough coupler should work well with this setup.

Peter

Re: Is the MMU2 finally starting to come together?

There is a solution to over-heating extruder; reduce the "holding current". However this feature was removed in firmware 3.5 🙁 and now holding current is set to the same value as printing current, and this will contribute to hotter E motor.

So.... either roll back firmware to 3.4.1 or run on stealth mode constantly?

Fun fun.

Re: Is the MMU2 finally starting to come together?

So.... either roll back firmware to 3.4.1 or run on stealth mode constantly?

As far as I understand it's only relevant in pause mode. During the print extruder is usually moving all the time.
With the new redesigned extruder head and always on the most recent firmware version, I had no more jams.

Re: Is the MMU2 finally starting to come together?

So.... either roll back firmware to 3.4.1 or run on stealth mode constantly?

As far as I understand it's only relevant in pause mode. During the print extruder is usually moving all the time.
With the new redesigned extruder head and always on the most recent firmware version, I had no more jams.

Holding mode is invoked after a about 125 milliseconds of no pulses being issued. And if you check most prints, there are many times where holding current is used and this really does keep the motor cool. During the summer, I experienced an E-motor temperature reduction of 18 degrees C.

Peter

Re: Is the MMU2 finally starting to come together?

Hi Peter. Did you replace ALL tubing for the MMU with the 2.5mm? I just got a 10m pack, so I'm looking to swap soon.

No. Just the Bowden and the feeds from the spools to MMU. The short sections in the MMU are the original ones and I have removed the PTFE at the top of the extruder with my amended extruder body - which also works without the lower Festo.

I think that getting rid of the lower Festo and small PTFE at the top of the extruder, along with the optical filament sensor was the best solution for me.

Peter

Just found this thread after getting really pissed off at the MMU 2 and ready to chuck it in the trash. But the larger diameter PTFE tubing does sound like a possibility. I found some 2.5mm ID PTFE tubing on Amazon and order some. I was wondering about your amended extruder body. Is there a link to the plans/model somewhere? I probably just missed it if there is one in the thread.

Re: Is the MMU2 finally starting to come together?

Just found this thread after getting really pissed off at the MMU 2 and ready to chuck it in the trash. But the larger diameter PTFE tubing does sound like a possibility. I found some 2.5mm ID PTFE tubing on Amazon and order some. I was wondering about your amended extruder body. Is there a link to the plans/model somewhere? I probably just missed it if there is one in the thread.

It is hidden in the thread now... It's on page 2.

I was trying to make the same thing which got rid of all of the filament sensor's holes, but there's no scad file for the new extruder. 🙁

Re: Is the MMU2 finally starting to come together?

Holding mode is invoked after a about 125 milliseconds of no pulses being issued. And if you check most prints, there are many times where holding current is used and this really does keep the motor cool. During the summer, I experienced an E-motor temperature reduction of 18 degrees C.

I just downgraded to 3.4.1 to see if that'll help. So far so good.. The motor's still getting warm, but we'll see how it goes. Next will probably be a heatsink if this doesn't get fixed.

Seems a bit backwards to use M907 Sxxx instead of using all separate currents and/or using M906 (just from my brief look into gcode, I'm by no means an expert... or even a novice).

Re: Is the MMU2 finally starting to come together?

Just found this thread after getting really pissed off at the MMU 2 and ready to chuck it in the trash. But the larger diameter PTFE tubing does sound like a possibility. I found some 2.5mm ID PTFE tubing on Amazon and order some. I was wondering about your amended extruder body. Is there a link to the plans/model somewhere? I probably just missed it if there is one in the thread.

It is hidden in the thread now... It's on page 2.

I was trying to make the same thing which got rid of all of the filament sensor's holes, but there's no scad file for the new extruder. 🙁

I went back and started searching again and found it. Thanks. Question about it though. I would still like to use the printer without the MMU so would like to still have access to the filament sensor. Do you think it would work the same if I removed the sensor and use the pass-thru filament cover so the PTFE tube goes further in the existing extruder? I'd rather not have to replace the extruder body if I don't have to.

Re: Is the MMU2 finally starting to come together?

I just downgraded to 3.4.1 to see if that'll help. So far so good.. The motor's still getting warm, but we'll see how it goes. Next will probably be a heatsink if this doesn't get fixed.

Seems a bit backwards to use M907 Sxxx instead of using all separate currents and/or using M906 (just from my brief look into gcode, I'm by no means an expert... or even a novice).

In start G-code:

M911 E16 ; Set E motor holding current
M912 E24 ; Set E motor running current

In tool change G-code (before unload moves) increase running current:

M912 E31

And after unload:

M912 E24

Although I am not certain you can do the last 2 in Slic3r 🙁

Peter

Re: Is the MMU2 finally starting to come together?

It is hidden in the thread now... It's on page 2.

I was trying to make the same thing which got rid of all of the filament sensor's holes, but there's no scad file for the new extruder. 🙁

Sorry, I don't do SCAD 🙁 Only Tinkercad for me - the others are way too complicated for my old brain...

Peter

Re: Is the MMU2 finally starting to come together?

I would recommend not ditching the filament sensor altogether. There’s a pretty high chance prusa will activate it again in the future to minimise failed mmu loads. I’d print something like my extruder mod instead, which keeps the sensor, makes it work 99%, and constrains the filament path so filament easily loads past the sensor chamber.
https://www.thingiverse.com/thing:3223513

Re: Is the MMU2 finally starting to come together?

In start G-code:

M911 E16 ; Set E motor holding current
M912 E24 ; Set E motor running current

In tool change G-code (before unload moves) increase running current:

M912 E31

And after unload:

M912 E24

Although I am not certain you can do the last 2 in Slic3r 🙁

Peter

I just (as in, earlier this afternoon, I was away all day) had another fail for the same issue again (broken filament, assuming from the Extruder motor).

Going to try the above on-start gcodes (I'm trying to print single material and am still having issues) and see if I have any upgrade. I don't have a temp probe to monitor the e temp though, which makes this difficult for me.

Re: Is the MMU2 finally starting to come together?

I just (as in, earlier this afternoon, I was away all day) had another fail for the same issue again (broken filament, assuming from the Extruder motor).

Can you describe "broken filament" in more detail? Hot extruder motor is usually only leads to jams during slow prints.

Re: Is the MMU2 finally starting to come together?

Can you describe "broken filament" in more detail? Hot extruder motor is usually only leads to jams during slow prints.

So at the idler/extruder bowden section of the extruder, the filament appears to soften enough from the heat to not grip anymore on the bowden, which leads to failed extrusion. When I use the LCD panel to Stop Print, the filament comes out from the bowden connection and then I have a portion of filament stuck from the bowden to the nozzle that I have to pull out.

I'll take a picture the next time that it happens. I'm re-printing my filament cover using a lower layer height to make better M10 screws. Then I'll start trying to print my longer-print again and see how it looks. (I'm using Peter's gcode in the start just to see how it works).

Re: Is the MMU2 finally starting to come together?

I'm using Peter's gcode in the start just to see how it works

There was something that I had forgotten (sorry)...

Either side of a tool change, the currents also need to be set:

M911 E0
M912 E0
T<EXT+0> ; Select extruder <EXT>
G4 P0
M911 E16 ; Set motor holding current
M912 E24 ; Set motor printing current

Although this may not be necessary, as the firmware could (should) do this for you.

And just one more observation on this, a setting of zero does not turn off the current, but sets if to 1/32 of the current range (about 17 mA).

Peter

Re: Is the MMU2 finally starting to come together?

Can you describe "broken filament" in more detail? Hot extruder motor is usually only leads to jams during slow prints.

So at the idler/extruder bowden section of the extruder, the filament appears to soften enough from the heat to not grip anymore on the bowden, which leads to failed extrusion. When I use the LCD panel to Stop Print, the filament comes out from the bowden connection and then I have a portion of filament stuck from the bowden to the nozzle that I have to pull out.

I'll take a picture the next time that it happens. I'm re-printing my filament cover using a lower layer height to make better M10 screws. Then I'll start trying to print my longer-print again and see how it looks. (I'm using Peter's gcode in the start just to see how it works).

Failed again, since I don't want to hijack this thread further, I've made a new post in the Mk3 forum: https://shop.prusa3d.com/forum/hardware-firmware-and-software-help-f64/extruder-motor-overheating-t26864.html