Bowden connection: simple M7 thread?

[joergen 2]

wow awesome! Your spring idea makes me think it would work well for leveling multiple extruder heads! Just pull the bowden up/down to get the nozzles at the same height. I too am wondering though how stiff is that spring? does it pull the head up when you go to the front left corner/ allow the head to go down when you are at back right?

If the spring actually works it might mean great news for multiple extruder ultimakers, you could even set up a servo to pull the print head up when not in use and then back down for printing...

if you take the spring idea to the next step, and make an outside M7 thread all the way up to where it exits the top lasercut board (and a bit further), and put a M7 nut up there that counter acts the spring tension below... this makes the nozzle height adjustable (1 turn is 1mm)... anybody up to try it?

[mm_build 1]

wow awesome! Your spring idea makes me think it would work well for leveling multiple extruder heads! Just pull the bowden up/down to get the nozzles at the same height. I too am wondering though how stiff is that spring? does it pull the head up when you go to the front left corner/ allow the head to go down when you are at back right?

If the spring actually works it might mean great news for multiple extruder ultimakers, you could even set up a servo to pull the print head up when not in use and then back down for printing...

if you take the spring idea to the next step, and make an outside M7 thread all the way up to where it exits the top lasercut board (and a bit further), and put a M7 nut up there that counter acts the spring tension below... this makes the nozzle height adjustable (1 turn is 1mm)... anybody up to try it?

Might be easier to thread a short plastic sleeve that fits over the tube, then glue it into place. (gluing teflon can be done apparently with a good cyanoacrylate glue (basically super glue but there are different grades))

[mm_build 1]

Just a quick update, there is a problem with this setup.

The PTFE tube is too weak to be threaded directly into the brass tube. I have had it blow out the side 4 times now. It seems to always fail at the top where the brass nozzle ends. I have been very careful threading the PTFE, but it has still failed. To make this work I would need to either reinforce the junction at the top of the tube, use a heavier tube, or most likely have something more solid and heat resistant between the brass and the PTFE. Which brings us back to PEEK....

I'm not giving up yet, but this is a step backward.

[destroyer2012 0]

Perhaps PFA will fare better? It is stronger than PTFE, right?

Just thinking out loud here:

The top of the brass nozzle is where pressure builds up from pushing filament. If you put a thicker tube around the outside of the threaded bowden maybe that will help reinforce the sides a bit right at that joint? Another thing is that by putting the spring there you are essentially placing a lot of stress on the bowden tube itself, as the hot end is now supported against the force of extrusion only by the strength of the bowden tube, and your spring is helping to break the tube too. The benefit of the PEEK is it gave a solid support for the hot end. A thicker tube, however, is moving back towards hotends mounted on PTFE round stock (which has been liable to creep and loosen and break.. that's why many people switched to PEEK).

Another interesting idea I've seen is to pound a brass pipe over the outside of a PTFE rod, thereby smashing the PTFE into the threads (grooves would be more effective) of your hot end. Then you can mount the brass pipe into the aluminum heatsink plate, and just shove your bowden tube into the PTFE rod (keeping it sealed by compression? Threads would probably work too). This method doesn't require PEEK and since the PTFE is forced into grooves/threads by compression it's likely to be stronger than just threading the hot end on by hand.