E3D Bowden fitting

Just converting an E3D v6 all metal to work with bowden. I've popped in the push fit cap you get, I assume you run the ptfe tube all the way down to the heat break?

The cap works by gripping the tube, and won't let it out unless you hold the cap in while withdrawing the tube. This means under normal operation there is about 2-3mm of play where the ptfe can move up and down. Is that normal? Seems wrong.

this is how the fitting works, by using compression.

these were usually used under full pressure, ie air pressure.
like lining a truck with air to the brakes, to the tanks, to the seat and suppension, etc,etc

because they carried it over from one application to this application, it hasn't changed the characteristics of the part.

eg. [www.youtube.com]

another eg. [www.pneumaticsolutions.com.au]

and because the readily available teflon tubing has what this industry needs, it and its fittings have been used.
the tube goes as far as the quick coupler, no further, you could just put tubing behind the fitting in the heatsink if you wanted, of try and modify the coupler.

hope it helps

Fair enough, I'll give it a go and just try and seat it deeply. I discovered you could put a thread on ptfe tube, which opens up some interesting possibilities if that doesn't work. I can't remember where I saw that...

RepRapPro blog converting omerod to dual extruder I think.

Threading would be fun to see. Make sure to upload results.

You can remove the play by inserting the PTFE all the way, then pulling it upwards along with the push fit, then keep the push fit where it is and shove the PTFE a couple mm further down.

Yes, that was to be my cunning plan. I've finally printed a new carriage and hot end holder, and wired up the extruder that will drive everything, so I'm pretty much good to go

Thomas Sanladerer mentions tension clips.
[youtu.be]

if you play from that link it starts at 1.42.

Quote
pushthatbolder
Thomas Sanladerer mentions tension clips.
[youtu.be]

if you play from that link it starts at 1.42.

Yes! Sold. I was a little concerned I'd get it taut and then never be able to remove the tube again.

I have fitted a 2mm bowden tube to my jhead/Wade extruder. I have found that not all of the pneumatic push fittings are the same. Quality varies between suppliers and even within the same batch. Some I fitted allowed the tube to move backwards and forwards during retraction. This allows a lot of hysteresis in the mechanism. Replacement of the fitting as soon as play is observed is easy and quick. They are not designed for continuous making and breaking, so have a finite life.

Edited 1 time(s). Last edit at 10/21/2014 10:46AM by dave3d.

I think you're right. I have about a million on order from various places on e-bay in a variety of sizes, so I'm ok if they go wrong. I can imagine having to cut the tube and use a new one if I get the tube really well pushed in and the push fit pulled up.

I've found a few useful things:

To search for them I used "pneumatic push fit Mx ymm" where x is the thread size that connects it to whatever, and y is the od of the tube it takes. Sounds obvious, but it was the Mx bit that proved helpful.

I've got a bunch that came with the Kraken. They're all 1/8th inch thread. Fortunately this seems to be a common imperial size as my tap and die set includes a 1/8th pair along with all the metric ones. So I've modified the design of my hot end holder to have a hole above the hotend into which I screw one of these fat push fits.