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MMU2s Cam position during printing  

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marktaraoliver
(@marktaraoliver)
Active Member
MMU2s Cam position during printing

Hi,

I've put rotation indicators on my steppers to see what's happening and have noted the following.

After the filament is loaded to the nozzle, and printing has started. I noted that the indicator on the shaft holding the multiple

gears for the materials was juddering. Implying that the gear and roller bearing was engaged to the filament and being pulled through. To stop the judder I released the spring loaded screw's on the MMU2 enough to stop the contact. However, this means that when the filament is retracted at the end of the print there is now not enough pressure to hold the filament in the MMU2 and retract effectivly.

Surely during the print process, the MMU2 CAM should disengage from the filament allowing it to run freely?

As this would mean the MMU2 Cam motor could be powered off and not be sat at 56Deg c and the head gears would have less work to do also resulting in a temperature drop, with overall better retraction of the filament by the MMU2 at the end of the print and the filament not being scraped by the gears on the MMU2?

Does anyone have any comments?

 

 

 

Posted : 03/07/2019 9:00 am
JoanTabb
(@joantabb)
Moderator
RE: MMU2s Cam position during printing

If the Cam motor was de powered during printing the MMU2 would have to re home and re select filament on every filament change, which would add extra time to the print for every filament change. 

Is the cam rotating off the filament select position  at the moment of transfer from MMU2 drive, to Extruder drive? the active filament should be free of the MMU2 hobbed wheels

 

Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 03/07/2019 12:43 pm
marktaraoliver
(@marktaraoliver)
Active Member
Topic starter answered:
RE: MMU2s Cam position during printing

Hi 🙂

No, the Cam seems to be staying in place. I will run another check tonight. 

It all loads to nozzle fine, then beings to print. This morning I noted the steeper indicator moving whilst printing, thought this as odd. 

I have been having jamming issues, but a bit of Google foo seems to imply I need slightly higher temperatures on the Mk3s due to the changes in the heat break design. And retraction settings are probably too aggressive for small prints 

I am used to using my AnyCubic I3 with larger retractions on a bowden set up. The Prusa is still al learning curve 🙂 

Posted : 03/07/2019 12:49 pm
JoanTabb
(@joantabb)
Moderator
RE: MMU2s Cam position during printing

I haven't upgraded to Mk3S MMU2S yet, on the Mk3 MMU2 I have swapped all of the PTFE tubes to and from the MMU, for 4mm x 2.5mm tubes  and added larger rollers to the filament support shafts on the filament reel holders, to reduce friction, and I have never used the Prusa Buffers.   
My Filament reels are on a shelf above the printer and the filament feeds down through the shelf in a short ptfe tube, then a longer tube delivers the filament to the MMU2.    the filament buffering occurs between the ends of these two tubes.

this is an image of the extra rollers I have on the filament tray shafts, they reduce the friction as the filament unspools  the narrow section rubs against the hub of the bearings preventing the  shoulders of the roller from rubbing against the static parts of the spool holder,

the printer to the left is my Mk2, MMU1 printer and the one to the right is my Mk3, MMU2 Printer.

there are nine rolls of filament on nine filament holders, on the shelf  , 4, for the MMU1 and 5 for the MMU2

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 03/07/2019 1:33 pm
marktaraoliver
(@marktaraoliver)
Active Member
Topic starter answered:
RE: MMU2s Cam position during printing

Mines running free for testing, But ultimately will be fed from a box under the units. With the rolls on a low friction bar 

 

Posted : 03/07/2019 1:38 pm
gnat
 gnat
(@gnat)
Noble Member
RE: MMU2s Cam position during printing
Posted by: marktaraoliver

Surely during the print process, the MMU2 CAM should disengage from the filament allowing it to run freely?

Want to be more annoyed? Leave your printer on for a few hours (long enough that everything should cool down) and then point your thermal camera at the idler motor. Not only is it engaged the whole time a print is running, it is engaged while the printer is idle too.

In addition to generating heat (and wear) on the motor, it also makes noise from the motor and PSU. I used to just leave my MK3 on all the time, but now I turn it off due to it being annoying.

MMU tips and troubleshooting
Stop SL1 tank leaks with a simple o-ring...
Posted : 03/07/2019 2:13 pm
gnat
 gnat
(@gnat)
Noble Member
RE: MMU2s Cam position during printing
Posted by: joan.t

If the Cam motor was de powered during printing the MMU2 would have to re home and re select filament on every filament change, which would add extra time to the print for every filament change. 

The impact of such would vary greatly based on the print. If the print has frequent changes then it would indeed be painful, if it only makes infrequent changes, however, it wouldn't be bad.

If they added a new gcode command to handle the disable and enable (with re-home) there is already a command (K I think?) to change the idler position. They could update PrusaSlicer to calculate the time between tool changes and if it is more than the time it would take to rehome the idler they could disable it and then re-enable it when needed. They could even predict when the idler would be needed and inject the enable command early enough that it can do that while the print is still running (which really means you want a padding factor rather than simply '>= idler reset time' for determining if it should be turned off). If done right you could actually see little to no additional time added to the print.

That's just what could be done, it's not something I'd want to see happen though as that adds more complexity and something else that can go wrong (e.g. it supposed to go back to tool 3, but goes to tool 1 instead) and be a pain to debug.

MMU tips and troubleshooting
Stop SL1 tank leaks with a simple o-ring...
Posted : 03/07/2019 2:25 pm
marktaraoliver
(@marktaraoliver)
Active Member
Topic starter answered:
RE: MMU2s Cam position during printing

Still powered when doing nothing, is just daft !

Posted : 03/07/2019 3:58 pm
marktaraoliver
(@marktaraoliver)
Active Member
Topic starter answered:
RE: MMU2s Cam position during printing

Upload does not seem to work here is link... https://drive.google.com/file/d/1YE9izsP6tanRpDgJN4OERm1vNBiMwSSkvA/view?usp=sharing

So here is my issue. MMU2S And the CAM is engaged during printing 

I have rebooted the power and reset the MMU2S....... Any ideas anyone!

This post was modified 2 years ago 2 times by marktaraoliver
Posted : 03/07/2019 4:14 pm
gnat
 gnat
(@gnat)
Noble Member
RE: MMU2s Cam position during printing
Posted by: marktaraoliver

Still powered when doing nothing, is just daft !

Here are some github issues about it, feel free to add your voice.

https://github.com/prusa3d/MM-control-01/issues/153

https://github.com/prusa3d/MM-control-01/issues/78

MMU tips and troubleshooting
Stop SL1 tank leaks with a simple o-ring...
Posted : 03/07/2019 4:14 pm
gnat
 gnat
(@gnat)
Noble Member
RE: MMU2s Cam position during printing
Posted by: marktaraoliver

So here is my issue. MMU2S And the CAM is engaged during printing 

I have rebooted the power and reset the MMU2S....... Any ideas anyone!

I'm not clear on what the issue is that you are having. Is it simply that those motors are doing something when you don't think they should or do you think it is related to printing problem?

I don't have indicators on my steppers so I honestly can't say what is happening during a print. My understanding is that the MMU is supposed to stop and let the extruder take over, but I haven't looked into it myself.

With as many issues as the MMU can have (especially getting started) I find it best not to go looking for new ones if you aren't having a problem 😆 

MMU tips and troubleshooting
Stop SL1 tank leaks with a simple o-ring...
Posted : 03/07/2019 4:21 pm
marktaraoliver
(@marktaraoliver)
Active Member
Topic starter answered:
RE: MMU2s Cam position during printing

The drive for the Idler keeps the bearing selected over the filament when the Exturdr on the printer should have taken over. I expected the filament to 'Run Free' through the MMU but its trapped, therefore the extruder, is having to fight the MMU2 motor

Posted : 03/07/2019 4:23 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: MMU2s Cam position during printing

the extruder should tell the MMU2 that it has received the filament ( as sensed by the IR sensor) and the MMU should slightly move the idler cam to allow free movement of the filament. most common problem is unreliable IR sensor setup. I modified my IR sensor board to add a surface mount LED and resistor between the +5 and output pins so i can see that it is working all the time. the display from the EINSY doesn't refresh enough to show intermittent failures at the sensor

Posted : 03/07/2019 5:31 pm
marktaraoliver
(@marktaraoliver)
Active Member
Topic starter answered:
RE: MMU2s Cam position during printing
Posted by: david.a66

the extruder should tell the MMU2 that it has received the filament ( as sensed by the IR sensor) and the MMU should slightly move the idler cam to allow free movement of the filament. most common problem is unreliable IR sensor setup. I modified my IR sensor board to add a surface mount LED and resistor between the +5 and output pins so i can see that it is working all the time. the display from the EINSY doesn't refresh enough to show intermittent failures at the sensor

Was tempted to do the same and add LED visual confirmation. Can you tell me your firmware, please? I have flashed the latest version and wonder if that's the issue. 3.7.1 - 2266 is mine.
If that matches then I will look at the IR sensor again. I have already had to add material to the arm so the sensor sees it. Maybe needs more 

Posted : 03/07/2019 6:22 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: MMU2s Cam position during printing

3.7.2 with mod for 0.9 deg X and Y motors and geared extruder

 

here's a good instruction for the LED mod

https://bunnyscience.dozuki.com/Guide/Bunny+and+Bear+(BNBSX)+MKS3+Geared+Extruder+Assembly/2?lang=en#s84

 

Posted : 03/07/2019 7:27 pm
marktaraoliver
(@marktaraoliver)
Active Member
Topic starter answered:
RE: MMU2s Cam position during printing

Ok solved it !

 

Flashed the latest firmware and now it is working 🙂

 

 

Posted : 04/07/2019 4:08 pm
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