Another update, as I managed to knock a few of these out on the CNC lathe today, not the best way to do this, as it involves manual tool changes, and setting up mini boring bars, thread cutting etc, but it was OK for proof of concept stuff, although more time consuming and more expensive with the longer machining time.
Good news, it worked first time, straight out of the box, despite modding the stepped collar to suit the tools available in the CNC shop, but next time I will tweak it slightly again.
I doubt this will invalidate your warranty if you are careful, but it goes without saying, that the Robox needs the filament ejecting, and be powered down unplugged from the mains, with the USB cord disconnected when you are messing inside.
Removing the LH stepper motor is pretty straightforward, but the screw furthest away benefits from a ball ended Allen key, and the side door removing. Cutting the shaft down so that it is 20mm proud of the stepped circular locating boss is all that is required for the LH side, and it is best to remove this. The RH side is able to be cut in situ with a small Dremel like slitting disc, although you want to pack the critical areas with a cloth, use a vacuum extractor, so that any metal particles don't contaminate your Robox. Ideally, you'd remove the RH stepper completely from the chassis and then cut it down, but it is a bit of a ball ache to be honest.
The pictures come from the Robox DM of @chazr33gtr who was keen to see the mods applied. Previously we used some generic motor shaft couplings off eBay, but they were far from ideal, the tolerancing was poor, so having the Nema 14 specs, I modded my stepped collar accordingly, and tested the fit, and whether it would fit in the LH side which is the most constrained as the plastic mouldings prevent a simple off the shelf collar being used.
The stepped collar was machined in one hit in the lathe and was done this way to maintain concentricity, as was the decision to use a single sided grub screw & thread the new rod into the collar to reduce the wobble effect.
To check the fit I used an old stepper, and on the LH side I placed the collar into the area, to see how much room was left.
After removing the LH stepper, the shaft was cut down, and the collar fitted in situ.
Then the printhead was lowered down onto the bed, with no PEI sheet to check the clearance available, and it was close. :)
After this was done the RH side was tackled, but this shaft had been cut down for the previously fitted eBay collar, so was a little too short for the stepped collar and the replacement threaded rod fitted a few days ago, at around 11-12mm from the boss. Ideally it wants to be 20mm like the other side. Pictures show the completed install, and the close up.
Enjoy the pimping @click, and the next step is to fit better material nuts, tailored to the thread form, and bespoke lengths of threaded bar to make an easy install kit for anybody who wants them. Strangely, this has made the Robox of @chazr33gtr seem quieter, and there is no more wobble from the Z drive than before either, despite its two piece construction, so teh design is robust enough :P
We are not sure of the finished price at the moment, but it will be affordable, and the target is to approach the same price as one Z drive stepper, for a complete kit for both sides. :o
The parts are not made in China either.
Posted : 28th October 2017 5:30 pm