Is there a way to bypass the MMU2S  

  RSS
Lvet
 lvet
(@lvet)
Trusted Member

Hello,

I need to print a part using a rather soft FLEX filament.

Is there an easy way of bypassing the MMU2S (i.e. loading the filament directly on the extruder like in the regular MK3S), without having to reflash the firmware? I am afraid that even in Single material mode, the MMU2S will be pretty rough with the filament.

Any ideas?

Cheers

Luca

Posted : 25/10/2020 1:28 am
jsw
 jsw
(@jsw)
Noble Member

Yes.

If you're just going to do a one-off print session, disconnect the power connection to the MMU2S and unscrew the bowden tube from the extruder.

Feed the filament into the hole where the tube was and gently press the top of the idler on the right of the chimney inward.  The hobbed gears will then load the filament in a similar manner to the MK3S without the MMU2S.

I installed a switch (the case for it is in the prints section here) to cut the power to the MMU2S, but you don't have to do that unless you plan on switching back and forth between regular MK3S and MMU2S-MK3S modes often.

No messing around with firmware necessary at all.

This post was modified 1 month ago 2 times by jsw
Posted : 25/10/2020 2:02 am
Lize liked
karl-herbert
(@karl-herbert)
Famed Member
Posted by: @luca-vicini

Hello,

I need to print a part using a rather soft FLEX filament.

Is there an easy way of bypassing the MMU2S (i.e. loading the filament directly on the extruder like in the regular MK3S), without having to reflash the firmware? I am afraid that even in Single material mode, the MMU2S will be pretty rough with the filament.

Any ideas?

Cheers

Luca

another possibility would be to disconnect the Rx/Tx data line from the MMU2 board (remove only data connector) and then reset the printer.

N/A is then displayed in the LCD menu.

 

 
This post was modified 1 month ago by karl-herbert
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 25/10/2020 2:19 am
Lvet
 lvet
(@lvet)
Trusted Member

Thanks for the great tips. 😀 

Removing the power supply and/or the data connector was a challenge, as you have to reach the little plastic lever on the pub side to release the connector. I will definitely place an additional switch to control this.

The other challenge, is that the FLEX filament that I am using is extremely soft, therefore the IR sensor doesn't get triggered (I had to extract the sensor and block it with a piece of paper).

I am having jams on the extruder every 10 minutes, but I guess I will have to find the optimal temperature / print speed combination. Also playing with the extruder gear tension might help.

Posted : 25/10/2020 9:39 am
jsw
 jsw
(@jsw)
Noble Member
Removing the power supply and/or the data connector was a challenge, as you have to reach the little plastic lever on the pub side to release the connector. I will definitely place an additional switch to control this.

This is EXACTLY why I added the switch, and whoever designed that little switch case obviously had the same thoughts.

One thing I may not have noted is that there are two unused tapped holes on the printer frame into which the screws for that switch case fit perfectly.  It's almost like something like that was once intended or considered.

Posted : 25/10/2020 1:28 pm
karl-herbert
(@karl-herbert)
Famed Member

@luca-vicini

i solved it by controlling the data lines Tx and Rx using Raspberry GPIO's, a bashscript and PrusaSlicer.If the MMU2 is not needed, the script switches off the data lines via relay, resets the printer and starts printing. After printing is finished, everything is reset automatically to default settings.

 
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 25/10/2020 5:33 pm
Lvet
 lvet
(@lvet)
Trusted Member

Thanks for the pieces of advice.

After several days of trying. I give up with this type of FLEX filament. Far too soft and after 10 minutes of printing systematically the extruder jams.

I was considering putting a bit of PTFE lubricant in the PTFE tube, in the hope to prevent jamming. But I am not sure it will improve anything.

Posted : 28/10/2020 8:10 am
jsw
 jsw
(@jsw)
Noble Member

You might ask here for very specific recommendation on the technique to print the brand and type of flex filament that you are attempting to use.  I do know that the MK3S is capable of printing some flex filaments and that users have done so successfully, even though I have not done so myself yet.

Posted : 28/10/2020 9:12 am
karl-herbert
(@karl-herbert)
Famed Member

@luca-vicini

I have already printed some flex material and made sure that the feed values (1,5mm3/s) are very low, set z-hop and retract to zero and use an absolutely clean hotend (new brass nozzle). I switched off the nozzle fan and experimented a bit with the temperatures. I also installed 4/2.5 PTFE tubes against some recommendations. The spring tension on the idler should be kept very low. The filament should also be dry. Keep infill as low as possible to increase flexibility.

The print was not perfect, especially on the bridges, but at least I didn't have any blockages on the hotend. Used material - Flex Semisoft from Extrudr.

 

 
This post was modified 1 month ago by karl-herbert
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 28/10/2020 5:58 pm
Lvet
 lvet
(@lvet)
Trusted Member

Thanks for the pieces of advice.

The material I am trying to use is Smartfil Flex. It's graded at 93A, and shouldn't be that hard to work with.

https://www.smartmaterials3d.com/en/flex-filament#/1-size-330g/8-colour-ivory_white/26-shoes_size-175mm

I used the "generic Flex" profile in Prusa Slicer and lowered the flow rate at 0.8mm3/s. My mistake is that I probably didn't condition well enough the filament roll before printing. I live in a fairly humid environment (100m from the sea with relative humidity of more than 80%). I will try again but I will leave the roll one night in a filament dryer 

Posted : 29/10/2020 8:33 pm
Share:

Please Login or Register