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Bondtech Prusa MMU2S MK3S Adaptation

by Leonrsmln31 Apr 15, 2019
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Do you need to use the PTFE from Prusa or the one included with the Bondtech BMG kit?

I shortened the Prusa one because of the 1.85mm internal diameter. The Bondtech hat 2mm internal.

Thank you, I just completed the upgrade today. I discovered that my PTFE tube was a 2mm inside the hotend which was probably causing most of my load and unload errors. I was my fault though for not double checking the tube.

"You need a change in the firmware because of the hight of the Bondtech extruder.
Define Z_Max_Pos 210 to Define Z_Max_Pos205."

Hey there, can you explain me where do I have to change in the firmware? I cannot find it in the actual 3.7.1 firmware

Comments deleted.

Thank you for awesome design, i solderd the led yesterday and its running like a dream now.
So take the extra time and doing the led, much easier to calibrate

Hei, very nice disign! But I have a question, where does the sensor tab have to be mounted? I cant see it on the pictures :/

Best regards

If you have the original door without the tab you can use the drill jig to drill a 3mm hole in the top of the door and then glue it in place.

Ahhh okay, so if I use the new door, its not be needed

Thank you for sharing your solution, I'm grateful. Parts printed clean and smooth with Generic ABS and cooling enabled. Top plate with .2 detachable/ only touching build plate came out clean. Look forward to installing. Will be sure to attribute.

Sorry, I am a bit confused. Why does the Max Z need to be change "Define Z_Max_Pos 210 to Define Z_Max_Pos205."? You mentioned because of the Bondtech Extruder, but I just don't understand why. Is it because of the top part of bondtech extruder hitting the frame? Thanks.

It's because of the build of the MK3s extruder it has a different height then the Bondtech. If you calibrate your Z height with the original MK3S firmware the Z-Axis stops to soon and you get an error message calibration failed. I you then check the Z height it is 5mm. So your Axis must go down 5mm further to see the sheet.

I see. Thanks for the explanation.

Can this be used with the Vekoj X carriage ends?

No problem, I use them.

Thanks! Any reason why https://www.thingiverse.com/thing:3560116 wouldn't be useable? I think this one makes it easier to disassemble from his original design.

X-Carriage for Bondtech Prusa Extruder MK3(+MK3S Add-on) (Revised X-Axis)
by vekoj

That's the one I'm using.

Thank you for the great solution.

My MMU2S just arrived but i am figthing with it.

Any hints for a good sensor calibration?

What Firmware do you use? I tried BGIOT-MK3S-BMG-1.8-3.7.1-RC1-firmware.hex and bondtech_fw_MK3S_3_7_0.hex but i am unsure if they are good for a MMU2S setup.

My setup: i3 MK3S, Full Bear Upgrade, Bondtech Extruder Upgrade

I still have to put my MMU2S on my printer. I'm not sure if I connect it to my MK3 or MK2.5. Both have my adaptation of the filamentsensor and my own firmware for the 0.9 degrees stepper.
With regards to the sensor calibration, I just turn the screw until I see the LED when the filament is between the Bondtech gears and it should be off when nothing is in between.

Thanx for the quick response. Currently i dont have a LED installed. So i am watching the sensor info. But i see the IR flipping while printing. Allready tried to adjust it but does not help.

You have to check if the fin on top of the door is high enough positioned in the sensor gap. Another possibility is that the filament used for the fin is transparent for IR light. You could try to put some aluminium foil around it to block the light.

The fin on the door was a little bit to high. i used a file to scale it a little bit down. at first it stuck a little bit.

But i think the position looks ok.

printed it with Prusament PETG Black

Did some small test prints, sensor is flapping but it works. No load/unload errors so far. Just started a 8h print with 2 colors. Lets see what happens ;)

Now i got a stable sensor signal.

I did it this way:

insert a 1.5mm Allen key instead of filament and then adjust the sensor that it just jumps from 0 to 1 not more

so its guaranteed that a 1.75mm Filament will trigger the sensor to 1

the signal is no rock stable and all works fine.

Good idea, glad it worked out for you.

Just a note. Its not really related to your sensor mod but i think it could safe "some" frustration:

i had big problems with filament unload jams. i thougth they are hardware related. but it is partly not correct.

Someone made a great profile for the MMU2. All my problems are gone, currently over 200 Filament Changes without any error :) with the standard Prusa Profile i get a jam at every twentieth change...


Also there is a Hardware Mod regarding the PTFE Tube inside the hotend. This tube gets expands over time and the filament tip gets bigger and cause a unload jam. He made some custom tube from Torlon. I have to test it myself, but it sounds plausible.

Yesterday I was about to throw the MMU2S out of the window... but i think i will keep it ;)

Doesn't this block the door shut and prevent inspecting (cleaning, ...) the extruder gears?

There is a opening in the sensorcover to allow the door to open.

I see you're using the 0.9º LDO pancake stepper with the Bondtech extruder. So far I had no luck getting the 0.9º motor to work: Did you need to do any firmware changes? It is specified for 1.4A of drive current as opposed to the 1.8º pancake supplied by Bondtech, which only needs 0.7A. When I connect the 0.9º motor, it clicks once and doesn't move.

I use the 0.9° stepper on both my printers, the MK3 AND the MK2.5. The only change I did was the Esteps. In my case it is working. I'm still learning to make firmware changes and see what I can find.

I really like what I'm seeing here so far. Just printed it, now to go digging for in my electronics box :)

Hi. Why 560 Ohm resistor? A green 3mm LED uses 3.2 volts with 20mA, so for use with 5V a 100 Ohm resistor would be needed. What am I missing? thanks

I wouldn't put to much load on the output, and as can be seen on the photos, there is more than enough light.

Hello , it works with the full bear upgrage ? Thanks you

I don't have a bear, but as far as I know uses the bondtech extruder the same topplate as the Prusa itself and that is used as base for this one. So I think it should fit.