Working with PTFE tubing
Assembly of the MMU2 requires me to push PTFE tubing into friction fit holes without deforming the tubing in any way. If the tubing is deformed in any way, there is a good chance the filament will jam in that location because the tolerances are so tight. Given that PTFE has very low friction, how am I supposed to get enough grip on it to push it into these holes when just about anything I can use will either slip or deform the tube?
Unfortunately I already deformed the tubing that came with the kit just trying to get them into their holes so I need some new tubing. Does anyone have a source in the USA?
Thank you for answering both questions.
Assembly of the MMU2 requires me to push PTFE tubing into friction fit holes without deforming the tubing in any way.
There shouldn't be any need to push ptfe tubes into friction fit holes.
If this is about the 5 ptfe tubes at the back of the MMU, these are clamped.
You should unscrew the 4 screws between the ptfe tubes and than insert the tubes and tighten the screws again.
RE: EBay…
Check out 2M 4M Teflon PTFE Pneumatic Tubing Bowden Tube 2mm 4mm ID OD or 4mm 6mm Air Hose https://ebay.us/p8BRR9
Consider buying ID2.5 mm (harder to find those) or even ID3.0 (unfortunately those deform very easily) to reduce friction….
If at first you don't succeed, skydiving is not for you.
Working with PTFE Tubing
That is what I thought. The instructions do seem to indicate that the tubing should be pressed into place as there is a hole to place them into. If you don't need to push them into place, why make a hole in the design? I was thinking of designing it differently so that rather than having a recessed hole, make the tubing mount flush and have a small conical feature to guide the filament into the channel.
⬢Take the first PTFE tube and slide it inside the MMU2S unit. All five tubes are bent in one direction, make sure the free end is now pointing up.
⬢There is a circular hole for each PTFE tube, you should be able to press at least 0.5 to 1 mm (0.02 - 0.04 inch) of the tube inside the hole.
⬢Continue by pressing in remaining four PTFE tubes.
Tubing
Thank you. I found a source for 2mm and 3mm bowden tube that should work. From what I have read, 3mm tubing generally works better than 2mm (or 1.8mm rather) tubing. What changes do I need to make so I can use 3mm tubes coming out the back?
Tubing
Thank you. I found a source for 2mm and 3mm bowden tube that should work. From what I have read, 3mm tubing generally works better than 2mm (or 1.8mm rather) tubing. What changes do I need to make so I can use 3mm tubes coming out the back?
3mm ID works better than 2mm but they get kinked very easily… I use ID 3 from spool to buffer to MMU and ID 2.5mm inside the MMU and from MMU to extruder (and the 1,85mm inside the hot end of course). That works nicely for me. If you replace the small tubes within the MMU you need to chamfer the inner edge facing the inside of the MMU, there are several tool available to help you do that ( https://www.prusaprinters.org/prints/34035-ptfe-multitool ). Otherwise the filament can catch on the edge during loading and cause problems. Also the pass through adaptor makes things easier and reduces friction: https://www.thingiverse.com/thing:3233579
If at first you don't succeed, skydiving is not for you.
Tubing
PS: If you push in the PTFEs on the back of the MMU you should see the edge of the PTFE reaching the little rectangular hole above the filament channel inside the MMU. This way you can check if they are correctly inserted and all the way in.
If at first you don't succeed, skydiving is not for you.
Thank you
Wonderful. Thank you for the information.