MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?
 
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MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?  

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kenneth.j5
(@kenneth-j5)
New Member
MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

I tried. I ran it for a year or more... first using it for multi-color, then just as a convenient spool selector... but honestly, I just got tired of constantly having to reset/reload/reset/reload. Yes, most of the time it worked, but it introduces so much randomness that I found myself printing less. Eventually, I'll try a palette and come back when Prusa has a serious upgrade available for this. 

Finally I unplugged it and took it off the machine. I will leave the cables on the control box for now in case I change my mind.

However... as a now "stock" MK3s, I am noting that my filament sensor doesn't seem to work right? The load / unload filament process is weird. If I hit "load filament" and tell it the material then it often goes right back to the menu, even though the extruder wheels are running. Then it will eventually ask if the extrusion is correct... but it seems a little odd as a UI. There is no "loading filament in progress" UI indication.

And "Autoload filament" is a lost cause, essentially due to the filament sensor on the extruder assembly having been moved I believe?

I guess what I am hoping is that I can somehow do the minimum possible changes to restore the MK3s to stock operation with a minimum of "rip the extruder apart" downtime. I can print with it as it is now, but I suspect that the experience is less than completely correct.

Thanks!
Ken

Posted : 09/09/2020 7:22 pm
m2tts liked
jsw
 jsw
(@jsw)
Noble Member
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

I use the MK3S in the stock mode more than I do with the MMU2S either in single or multi mode.  Most of the time I have the tube between the extruder and the MMU disconnected and feed the filament right into the extruder.  I have a switch on the side to turn on/off the MMU.

The filament sensor will work, but as you've probably discovered, it is sensitive and the adjustment is awkward and imprecise.

One of my do-eventually projects is to install the remixed idler which has a screw for more precise adjustment of the sensor.

Autoload will work fine by gently pressing the idler inward and inserting the filament.

If the sensor is wonky, you can easily disable it in firmware.  You will lose the ability for it to halt on filament run-out and ask for more food.  😉

Posted : 10/09/2020 1:04 am
m2tts
(@m2tts)
Eminent Member
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

I'm looking to do the same thing and wondering if I can leave the MMU2's extruder sensor in place as I have no idea where I've put the stock one when I installed the MMU.

Posted : 20/10/2020 1:25 am
Area51
(@area51)
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

You can leave the MMU2 sensor in the machine, but it will only detect filament runout when it is too late to do anything. The filament has to pass the gears before detection.

I had mine MK3S in that configuration for over a year and got some false filament runout - decided to turn off filament sensor and it worked fine.

Have a look at my designs on PrusaPrinters ;)...
Posted : 20/10/2020 2:09 am
m2tts liked
Ruud
 Ruud
(@ruud)
Active Member
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?
Posted by: @jsw

I use the MK3S in the stock mode more than I do with the MMU2S either in single or multi mode.  Most of the time I have the tube between the extruder and the MMU disconnected and feed the filament right into the extruder.  I have a switch on the side to turn on/off the MMU.

The filament sensor will work, but as you've probably discovered, it is sensitive and the adjustment is awkward and imprecise.

One of my do-eventually projects is to install the remixed idler which has a screw for more precise adjustment of the sensor.

Autoload will work fine by gently pressing the idler inward and inserting the filament.

If the sensor is wonky, you can easily disable it in firmware.  You will lose the ability for it to halt on filament run-out and ask for more food.  😉

The switch sound like a really good idea. While multi-material prints and single material prints with the MK3S & MMU2S both have succeeded  (I am impressed by the performance of the upgrade) the MMU2S does introduce unnecessary complexity and potential failures in single material prints. Also my feeling is that Flex via the MMU2S is daunting (haven't tried it yet).

Can you share more details about the switch? Did you put it in the power cable? Only switch both positive (red)? Did put it in the MMU2S or on the printer frame?

Thanks for your help!

Best Regards, Ruud.

Posted : 25/10/2020 10:37 am
Area51
(@area51)
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

To temporary disconnect the MMU2S unit, the two shown plugs must be disconnected, either physical or by inserting a switch in the wires:

I have marked the plugs on my MMU2S with yellow and green dot to make it easier to get it right when assembling again.

In theory it should be enough to just disconnect one, but I disconnect both.

Only disconnect/reconnect when the power is off.

Have a look at my designs on PrusaPrinters ;)...
Posted : 25/10/2020 12:36 pm
jsw
 jsw
(@jsw)
Noble Member
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?
Posted by: @ruud-kapteijn
  The switch sound like a really good idea. While multi-material prints and single material prints with the MK3S & MMU2S both have succeeded  (I am impressed by the performance of the upgrade) the MMU2S does introduce unnecessary complexity and potential failures in single material prints. Also my feeling is that Flex via the MMU2S is daunting (haven't tried it yet).

Can you share more details about the switch? Did you put it in the power cable? Only switch both positive (red)? Did put it in the MMU2S or on the printer frame?

Thanks for your help!

Best Regards, Ruud.

I don't know if I would even attempt flex filaments with the MMU2S.  I've only used it with the same 'species' of filament on each spool.  I have also added those thumbscrew extensions in order to open/adjust the MMU more conveniently if needed.

The switch is a DPST breaking both + and - of the power.  Breaking the two data lines (or even just one of them, pick one) on the data connector would probably have the same effect, but with the MMU2S powered up.  There are some who may say that leaving the data lines connected while breaking only the power will molest your children and keep the country from winning the war, and we may have to agree to disagree on that.  I've found that breaking the power is very effective with no other issues.  It's a coin-flip, and both approaches will cause the main board to sense that a MMU is not attached and assume the non-MMU state.

The switch is mounted on the printer frame, rear, just above the circuit board compartment.  Whoever designed the switch case realized that there are two unused tapped holes with the correct spacing, almost as if something like this may have been intended in the original design.  The fabric-wrapped cable is run through the little switch case and carefully pieced out to attach the power leads to the switch.

I recently posted this photo on a similar thread, but not here, so here it is.

 

 

Posted : 25/10/2020 1:23 pm
Ruud liked
Ruud
 Ruud
(@ruud)
Active Member
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

Briljant! Thx.

BR, Ruud.

Posted : 25/10/2020 6:14 pm
Area51
(@area51)
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

A switch like this Self-Locking Push Button Switch 8PDT 8 Pole 24 Pin 1 Position could be used to disconnect all wires at once. This type of switch was always used in old stereo amplifier setups.

Have a look at my designs on PrusaPrinters ;)...
Posted : 26/10/2020 12:29 am
Ruud
 Ruud
(@ruud)
Active Member
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

The switch just needs to interrupt the two black power cables. They both can be connected to one switch (the two black cables are interconnected at the power-supply side anyway). Please note that interrupting the red power cables does not work (as I have found out).

Posted : 26/10/2020 3:01 pm
Area51
(@area51)
RE: MMU2S Removal, do I need to reverse the hot end changes to get the filament sensor working?

It is not advisable to disconnect only one of the power wires as the main board in the MK3 could draw current through the signal lines from the MMU2 and over time fail.

Maybe it is harmless maybe not, only disconnecting one power wire - it depends on how well the input/output circuit is designed on both boards. In this case I don't think there is much protection, but I haven't checked the schematics.

Have a look at my designs on PrusaPrinters ;)...
Posted : 26/10/2020 11:04 pm
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