RMU Mk3 Customer Feedback

We really like to see what people have done with the RMU Mk3 Filament Buffer. Of course we designed it to fit on the frame of the Prusa i3 and to be compact and easy to use. But we also know that for some people, they have very little space for their printers and even with how compact the Filament Buffer is it won’t work for everyone.

Innovation is the core of the 3D printing community so here are a couple of examples of what people have done with their buffers.

RMU MK3 Thoughts and experiences...

Mike H: (From Facebook)

Today I finally finished printing all the parts for the RMU MK3. I purchased the STL from Alan Wedge at https://filamentbuffer.co.uk/
I went with the MOD-T version because I have a Lack V2 enclosure and I thought this may be the best way to load the filament from the holes in the back of my enclosure.
The biggest frustration I had with the whole experience was not anything to do with the instructions or parts, but my own *slap my head* moments. I failed printing a couple of the larger parts and that was my fault. One issue was I had a loose wire on my board so half way thru the print my printer reset. After trouble shooting that it was smooth sailing for printing.
I had all the hardware on hand that was needed so I assembled and attached it to my printer. This gave me a chance to clean out all the dust and perform some routine maintenance on my printer.
After assembling and attaching to my printer I proceeded to put it in my Lack V2 Enclosure. IT FITS! Well you have to shift it to the right just a bit to clear the prop stand that hold the lid up. After carefully checking clearances I cut the prop stand by 6 cm and now the RMU MK3 fits just fine.
Ok, all honesty here I actually put the printer in, moved it over to the center by habit, and then went about putting in the PTFE tubes. Not thinking I promptly closed the lid, breaking off the 6 cm of prop rod when it struck the RMU in the process. “Happy Little accident” and now it fits centered in the Lack V2. (The RMU was undamaged)
Currently I have a 4 color print started, and it is on the first color so it hasn’t had its first filament change yet, but soon. Just by the looks of it I think it will work just fine.
Final thoughts…..
1) If you have it in the Lack V2, be careful opening the RMU MK3. I opened it and because the back is enclosed, the PTFE tubes going to the MMU2s kinked. This can be avoided by gently opening the RMU MK3 and pushing the PTFE tubes down. I don’t think I would have this issue if it was in the open air.
2) Lack V2 Prop rod should be shortened by 6 cm, that way your RMU MK3 will fit with the printer centered in the enclosure. (If you want it centered, if not just scooch it over enough to clear the closing rod.
3) Cost, some people complain about the RMU MK3 being too expensive, and not open source. My thought on that is a lot of work seems to have gone into making this. People charge for STLs all the time and people have the right to charge for a product. If you think it is to expensive than look at some of the open source products. This product fit the bill for exactly what I wanted/needed for my MK3s and MMU2s so I purchased the STL and supported the designer. Please don’t post negative comments about price, of course you can disagree but please be polite.
4) As a final thought I would like to thank Alan and the crew for creating exactly what I needed. Keep up the great work, be safe, and congratulations on the launch of your product.
5) While writing this, my printer did a filament change with no issue and is happily printing the 2nd color now. Now just to wait and see how well it performs.

Bob H:  (From Facebook)

Finally got My MMU2 up and running this time with the RMU MK3 Buffer Well Pleased

Manuel M:  (From Facebook)

I Love it 🙂

11 Responses

  1. I am looking to modify the design to make the sides solid and add volume to incorporate desiccant. Has anyone done the same?

    1. Hi Frank, No one else has tried but it will be very difficult to make it airtight. You are welcome to have a go.

  2. Printing full time now over a week and not a single error when switching hundreds of colors. Love it

  3. I tried it out finally today – I had just a little problem, I’m using the side-fed version, and one filament I crossed the filament over itself (going around the pulley), so it took too much effort to pull on and ground the filament in the MMU. Once I realized what was going on and fixed that, I was able to print flawlessly. Thanks for making this project, it made a huge difference for me.

    1. Thanks Mike. It’s possible the bearing is too loose in the idler wheel. In this circumstance there can be some movement in the wheel that allows the filament to get past the wheel when loading. It doesn’t cause a problem in use.

      To test this you can remove the wheels from the door unit and see if the bearings are loose. If they are a short pierce of PTFE tape on the outside of the bearing will stop that movement.

  4. Why are the bearings so loose on the axis pin? The axis pin has a od of 7.7mm and the id of the bearing is 8mm.
    So the whole bearing rotates (with lots of play) on the axis pin and it doesn’t function as a bearing, just a loose collar.
    That seems to defeat the purpose of having a bearing.
    Appart from that, nice design!

    1. HI John,

      The bearings are intended to be a slip fit over the axis pin. our axis pins measure at 7.8mm with the CAD showing 7.8. we have found this size provide good stability without making the top assembly difficult. the 0.1mm undersize shouldn’t make a difference to the assembly or function but I would advise checking your printer for slight under extrusion.

      This tool is helpful: https://teachingtechyt.github.io/calibration.html#flow

      1. Hi Alan,

        Thanks for your reply. I reprinted the axis pin slightly larger. The diameter is now 7.8mm (+0.02 / -0.0).

        It’s still very loose in the bearing. The inner sleeve of the bearing just slips on the axis pin with a lot of wobble. So it’s not acting as a ball bearing, just a slip bearing. Don’t know if that will cause a problem with wear on the axis pin. But it will probably work fine.

        I’m waiting for my mmu2s (on back order with Prusa). I’ll try the filament buffer then.

        Thanks again for a really nice design.

        1. Most of the play is taken out by the flange spacers built into the top door that is then constrained by the axis pin washers. it should not be a problem. Let me know if you find anything else worth noting.

  5. If you’re hesitating on spending the money on this buffer. DON’T! Absolute life saver when it comes to the MMU2’s machines.
    The RMU MK3 Buffer is compact, well designed and works straight away. Did not have to tinker with anything to put the unit together.

    I have had no load or unload issues since buying and printing the unit for my Prusa Mk3S.

    Light weight, compact and fits nicely to the Mk3S.

    Well done to the team at Wedgepoint.

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