Magnetic MMU2S PTFE Bowden Tube Interface for Original Prusa Enclosure

Summary

This PTFE Bowden Tube Interface is designed for

• ease of use and maximum comfort during change of filaments on the MMU (by using a magnetic filament interface)
• minimal need for extra filament buffer (for filament path between MMU and enclosure back plane)
• nicely matching the Original Prusa Enclosure design
• best use in combination with my buffering dry box, based on Ikea Samla boxes

Main Characteristics

• serving all MMU2S filament paths from the backside of the Original Prusa Enclosure
• guiding the PTFE tubes in a direct, clean, symmetric and short way without unnecessary bowden tube curves
• avoiding the (IMHO not so smart) default way through small openings on the side of the enclosure
• offering a magnetic coupling of the buffered filaments paths
• no need to open the enclosure for filament changes on the MMU
• nice design for the integration to the enclosure, remixed from the optional transport handles for the enclosure
• (re)use the default cutout geometry of the transport handles for a new cutout of the backplane

Background

I designed the Ikea Samla 45l Filament Buffering Dry Box to be able to buffer a bit more of filament than needed for a pure MMU push back of filament during unload of the extruder. Reason is that during a filament change from the outside of the enclosure the additional distance from MMU to the backplane of the enclosure has to buffered as well. So I really recommend to have a look to my dry box that addresses that. Then a filament change for the next print neither needs you to open the enclosure nor needs you to open a dry box! I rather thought quite long on how to solve that. Finally this project in combination with the dry box solves all of this.

Parts and Function

The interface consists of 

• a modified transport handle as supplied in an extension to the Original Prusa Enclosure (that serves as mounting point). As seen here on the picture, a cover for the transport handle is used as well.
• a magnetic tube interface (that is screwed on the modified transport handle). 

Modified Enclosure Transport Handle as Mounting Point

(outside view with mounted cover)

(inside view)

I wanted to take the transport handle design, because then the needed new cutout on the backplane is identical to the cutouts of the side panels. So you get a nice optics and you can the layout of the cutout can easily copy it by laying the side panel onto the back panel to mark it. 

First I wanted to reuse the transport handle directly w/o modification, but when testing it I saw that my numbering of the magnetic ends of the filament tubes from my dry box where partially hidden. The transport handle was too deep (which is ok for getting grip with your fingers). So I remixed the inside part of the handles for less depth so that the numbers get visible on the outside of the enclosure. The rest of the handles did not change. 

Magnetic PTFE Bowden Tube Interface

I remixed my original design from Magnetic MMU - Drybox Interface resulting in two parts: one with the magnetic interface for the outside and one with threads for PC4-M10 couplers as I wanted to avoid glueing the tubes in or rely on the friction of the tubes in the interface only.

And this is how it looks currently from the inside of a Prusa Original Enclosure:

Please note that I used the horizontal MMU mount to have a direct connection through the bowden tubes from the MMU to the magnetic interface.

Backpanel with additional cutout

The downside of the design presented here is, that you have to create an additional cutout on the back panel. To make that part as easy as possible I'm just reusing the cutout design of the side panels for the transport handle. Just lay a side panel on the back panel an draw the cutout as copy from side panel to back panel together with the additional center screw hole. Be sure to use the right position (mid of the upper side) on the back panel. 

Of course the best point in time for doing this is during the assembly of the enclosure with unmounted planes. As you will not need the side openings on the back panel you can also do it like me and just perform a copy of the whole back plane. As I also did not like the unused hexagonal cutout I went for a new, slightly thicker 3mm back plane in black. 

The identical cutout allows for reusing the transport handle design.

Reused Projects

• Transport handle Cover for Original Prusa Enclosure just offers a nicer and more stable handle. Recommended!
• Original Prusa Enclosure push rivet for 3mm planes (optional) 

Remixed Projects

• Transport handle for Original Prusa Enclosure in a thinner version serves as central mount point on the back plane.
• Magnetic MMU - Drybox Interface is my original version of the magnetic drybox interface.
• Knurled PC4-M10 PTFE Drybox filament pass through was reused just because of the right thread for the couplers.

Related Projects

• Original Prusa Enclosure
• Ikea Samla 45l Filament Buffering Dry Box V2
• (Beta Test) Magnetic MMU Transport Handle for Original Prusa Enclosure Interface
• MMU2s Horizontal Mount 

Outlook

There will be a “Magnetic Filament Dock for Original Prusa Enclosure” as extension to this project. As you can see on one of the pictures, the caps of the mounted tubes nicely snap on the metal frame of the Original Prusa Enclosure. Even a closed filament end holds on the frame. But for even more not used tubes from additionaI dry boxes I plan for a dock that can hold the tubes (all with magnets on their ends) in a magnetic dock mounted to the back of the enclosure. Stay tuned…

Non-printed Material

• 5 neodymium ring-magnets with a proper chrome or nickel coating : 4mm inner hole, 10 mm outer diameter, 5 mm height
• Some meter of PTFE tube (outer 4mm, inner 2-3mm) from MMU to enclosure interface, depending on your setup
• 2 Screws Torx / M4 x 16 mm DIN ISO 7380-1 with nuts and 2 optional washers each