Update 18 August 17
Just about 2 months on and still reveling in the world of Bowden tube free printing. NinjaFlex speeds are up and PETG is virtually hairless. The body of the Nimble indeed seems to do a fine job of seating the PTFE tube in the bottom of the barrel via the through bore Guide Bushing. Haven't had a hint of a jam. Here is a version to put a Nimble on the Prometheus V2.
If you are "mad" for direct extrusion and the Nimble and "mad" enough to be living with a small fleet of accelerometer equipped hot ends, you might have printed out the Mad Hatter. In which case, if you installed the headers and plugs for the fans on your accelerometer boards,
you might find that (as of 23 June 2017) the Mad Hatter headroom is a little shy and one of the nut retainers interferes with the HE fan plug.
Now of course there would be no point being "mad" about this, (eta you could use Turpinator's solution), or you could get crabby, the Crabby Cap that is...
Crabby has a lofty 9.5mm clearance over the fan plug region and 2.5mm over the rest of the board. The extruder is rotated about 30deg to clear the HE fan plug.
In addition to claws for elastic straps to cinch down the whip, the whip plug port is shrouded to further reduce motion (should one not have the locking connector).
The cap mounts to the hotend via the outer mount holes (M3x20mm - will self tap) which allows the accelerometer plate to remain attached whilst fiddling around which should reduce the risk of pinching the wiring for the few who might approach my level of clumsiness. Current model utilizes threads tapped into the cap. At some point once the dust settles on the design (the claws and elastic straps are just a brilliant idea at the moment...) i will post a retained nut version for those so inclined.
A guide bushing (8.5mm minor OD, 16mm major OD) supports the PTFE tube and ensures concentricity between the hot end bore and the Nimble groove mount adapter. The inner diameter can be through bored to allow passage of the PTFE tube up to the bottom face of filament guide on the body. This relaxes the axial tolerance of the bushing between the top of the hot end and the bottom of the groove mount adapter but axial retention of the PTFE tube is only across half of its face and the corresponding small area on the filament guide.
Alternatively, the inner diameter of the bushing could be shoulder bored allowing axial retention of the PTFE tube across the full face. However with this approach, the axial length of the bushing would need to be fairly precise in order to impart the load to the groove mount adapter without axial play and subsequent risk of dread "puck' formation.
It would be nice if this arrangement is sufficient to eliminate the need for seating the PTC connector as i notice when it is tight enough to avoid slippage, the inner diameter of the PTFE tube gets a little restricted and little shards of PTFE are to be scrapped off the outside of the tubing by the metal jaws of the PTC.
The shards would seem to be small enough such that they may work their way down the outside of the outside of the PTFE tubing where they could join the filament path....
The first prototype trial will use a through bore guide bushing with a major diameter length of 5.75mm, minor diameter length of 3.3mm (over all length of 9.05mm) which just shoulders up (as near as i can determine without plasti-guaging it) to the groove mount adapter and the bottom face of the filament guide on the extruder body. The PTFE tube is ~0.3mm proud of the top of the guide bushing but this "preload" is easily compressed by the Nimble as the mount bolts are tightened and everything appears to sit squarely. The PTC is unset, so it will be interesting to see how the HE280 performs.
With the help of ramai's guide (thank you very much!) for Repetier/RAMBo Nimble setup, hope to be printing some Ninjaflex whip retention straps tomorrow.
For those who would be Nimble Millners, here are the empirically (caveat emptor) derived dimensions used.
If the precise dimensions for the relationship between the filament guide centre and the body mounting holes are available somewhere, please let me know. I was unable to extract them from the dfx file for the basic adapter but it doesn't take much to stymie me...(eta... especially if the mounting information is in plain sight )
Any comments or suggestions for improvement are will be appreciated.
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