Fixed my Z drive is...
 
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Fixed my Z drive issue (worn threads and nuts) with custom parts

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Charles Jackson
(@chazr33gtr)
Reputable Member

Ok so... my warranty will be void on the z drive motors.. but hey ho they out of stock so what was i to do!.

@17bt and I sourced some 5mm x0.5mm pitch threaded rod and some high quality <span style="text-decoration: underline;">dissimilar </span> metal nuts and a 5mm bar collar.   Modified and machined the parts appropriately and cut the RHS Zdrive motor so only 15mm of non threaded shaft protruding from the motor housing. Upshot, hey presto a working replaced right hand Z drive.    Z test works a treat, Gantry level is spot on.

The Left Hand side shaft is also a bit tired but was working, interestingly I swapped the nuts on it for these <span style="text-decoration: underline;">dissimilar </span>metal nuts and the slight bind it was having has gone too.  Didnt fancy the ball ache of pulling that motor out of the case.

These nuts are the mutts nuts as they spin much smoother on the OEM shaft as well as my aftermarket sourced rod.

So I now have a use for my printer other than a filament drier (haha @17bt).

 

See pic to show the Mod. Blue aluminium thing is the coupler.  also going to do it for left side but space is a lot tighter for clearance between motor casing and x-carriage end rail.  Pic also shows the 24V cable mod with thicker wire soldered straight to the head carriage pins and cable tied to the cable guide.

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Topic starter Posted : 25th October 2017 9:49 pm
Mike
 Mike
(@17bt)
Prominent Member

What @chazr33gtr didn't say was a charitable soul gave him his secondhand Nema 14 Z drive assembly that had a couple of graunchy bits on it, but nowhere near as knackered as his, and this same kind soul swapped out the lower drive nut for one of these special ones, and the Z test didn't fail like it was doing before.

The factory set up has been a pet peeve of mine, and I feel somewhat vindicated by this approach, despite not getting anywhere near the hours of use of some, and only owning two Robox printers. The next thing is to refine this slightly, with a CNC upgrade part, which has now been drawn and emailed off to the CNC chaps down the road, as I type this.

Needs must when the devil drives :)

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Posted : 25th October 2017 10:12 pm
Charles Jackson
(@chazr33gtr)
Reputable Member

@17bt

I thought it was was of those anonymous charitable donor situations lol!..  but yes thanks very much,, you helped me out of a right old pickle.   Ive just done a print and its come out spot on.  Its also seems to be printing quieter too.. dunnot wether this is due to better alignment of the xcarriage now and the nuts..  or im just going nuts!.

A larger bottle of some whiskey or other will be on its way as a thankyou..  especially as the now non-anonymous donor also paid for the custom bits!

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Topic starter Posted : 25th October 2017 10:53 pm
Mike
 Mike
(@17bt)
Prominent Member

@chazr33gtr Glad you've not just got a filament dryer anymore, and hope you get to the bottom of the Y limit switch being always on. Maybe you should raise a support ticket, and hopefully CEL have got them in stock, or we'll be reflowing one of those heavier duty CPC items. :LMAO

Those nuts were definitely smoother than the originals threading down the shaft, but even though I did think it was quieter on the Z test this time than before the changes were made, you wouldn't think the nuts would be the reason, even though they were the only change made.

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Posted : 25th October 2017 11:33 pm
Pete
 Pete
(@pete)
I am Pete Admin

Do you have a link to these magical nuts?

I can probably rig up a test to see if they hold up after a lot of abuse.

For official support please create a support ticket using this link www.cel-robox.com/support/

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Posted : 26th October 2017 9:15 am
uhuglue
(@uhuglue)
Estimable Member

@17bt @chazr33gtr Just get a room, you two! X-D

Nice work! I've been having problems with the threaded rods and nuts since day 1 of receiving a KS Beta unit.

Switching over to a dry teflon lubricant as per Ben's advice seemed to fix things (going on over a year and half without issues iirc), but its always reassuring to know that there are alternatives if and when things go south.

It is also nice to be able to swap out parts as needed instead of having to replace a whole assembly. As it is, I have a couple of stripped rods attached to the working steppers - seems a waste to have them sitting idle.

Might I ask where you got all the necessary parts? Alternatively if you plan to sell these as a kit, I'd be interested.

And now I'm just waiting for the results of @pete 's stress test!

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Posted : 26th October 2017 9:35 am
Mike
 Mike
(@17bt)
Prominent Member

Might I ask where you got all the necessary parts? Alternatively if you plan to sell these as a kit, I’d be interested.

@uhuglue I've asked the CNC guys to make some extra, so yes, I will put a kit together for you, as I'm of the same mindset, and it's a shame to waste those Nema 14 steppers. The only reason I am CNCing them is they need to be bespoke as the LH side is quite constrained and is forcing a different solution. :)

It might even be a production upgrade ;) :LMAO

PS Like the humour too, Forum has been a little dry lately!

EDIT @pete I'll send you some in the post tonight when I get home, but they did feel pretty good on a worn shaft, and being deeper they appear to bridge the damage on @chazr33gtr LH Z screw and the "graunching" disappeared. I have noticed the screw shafts must be very clean, as any grit will lock the nut. Also as they are slightly thicker they do change the backlash spring tension, but in a finger rolling test, there was no apparent extra effort, and it definitely felt smoother than the originals. FWIW, and being observational. :)

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Posted : 26th October 2017 10:09 am
click
(@click)
Noble Member

Well done guys! It is quite inspirational seeing Robox being pimped up! :)

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Posted : 26th October 2017 7:17 pm
Charles Jackson
(@chazr33gtr)
Reputable Member

@click

Thanks for the feeback much appreciated :-) .  Will have more of a play in the coming weeks few other ideas up our sleeves.  If only my time wasnt eaten up with my Aerospace career a wife and baby daughter i might do something really dangerous lol!.  But defo this idea of mikes and mine, the silicone wire 24v cable and my tweaks to the dual material head all help IMHO for a better print experience.

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Topic starter Posted : 26th October 2017 9:43 pm
Mike
 Mike
(@17bt)
Prominent Member

Just a teaser really, as I hope to have by next week a fully working prototype of my thoughts on the Z screw area, and I'm very pleased to be having discussions and working with an educated chap, who understands the science of threads and the tribology involved.

Feedback from telephone conversations this morning with @chazr33gtr is that the temporary RH bodge is doing very well, and the grumbling worn LH Z screw with these new nuts is producing very good models and better layering than he's seen to date, which is all rather encouraging.

One of the side effects of this project is I can definitely improve the performance and smoothness of the existing operation, as I am not tied to the original Z screw design, plus it could lead to some other interesting "skunkworks" aka Robox Warranty busting hacks further down the line. :o

Keep you posted. :)

 

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Posted : 27th October 2017 11:55 am
Mike
 Mike
(@17bt)
Prominent Member

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.

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Posted : 28th October 2017 5:30 pm
Charles Jackson
(@chazr33gtr)
Reputable Member

@ 17bt Awesome job Mike this afternoon.... must book a room sometime LOL!  the parts fitted now look like they are production parts and meant to be there.  The printer is quieter.. but i too not 100% sure why.. maybe the xcarriage is better aligned??

Anyways I did a simple print to check layering ..a square tube,, i think it came out pretty well.. printed in bog basic cheapo PLA filament.   The eagle eyed will see a slight change in surface quality towards the middle of the print.. i just player with the feed rate multiplier and put it up to 110% for a little bit.

 

Well chuffed that my printer back and working and can get on with stuff again now :-)

 

 

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Topic starter Posted : 28th October 2017 10:31 pm
Mike
 Mike
(@17bt)
Prominent Member

Just an update, the test batch of bespoke M5 x 0.5mm threaded rod lengths and phosphor bronze nuts have been ordered, and @pete I will send you the BZP nuts when I get to a Post Office, as currently onsite 05:30-20:00.

I have 18 sets of stepped collars available as I type this post.

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Posted : 1st November 2017 1:57 pm
Wellmeadow
(@wellmeadow)
Estimable Member

@chazr33gtr - great work. I've looked through and can't find any links to the nuts or the coupling. Can you post them here? Also, are you selling the small turned coupling you have made?

Thanks.

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Posted : 5th January 2018 10:33 am
Mike
 Mike
(@17bt)
Prominent Member

@wellmeadow I did ask the threaded rod supplier to make some phosphor bronze nuts, and he made a test batch of two bespoke screw shafts for me to test, but as there was next to no interest, I have not pursued it further. I have had no issues since, so no need to strip things down either.

I do have some couplings available, and the nuts I used originally are still working in my printers no problem, as they are in @chazr33gtr printer too. I was on a silly work schedule, and I never sent the nuts to @pete either.  The nuts I sourced are marginally deeper than the OEM ones, and the BZP coating introduces a sacrificial surface, and I have 4 here if you need them.

If you need some threaded screws I would have to order some, but the whole process can be tackled by a careful tinkerer, working on the principle of least disturbance and using a Dremel with slitting disc for the trickier RH Z shaft replacement, it really isn't beyond most folks.

I have been a little preoccupied with other stuff since this thread started, so apologies for my tardy response to this one.

 

 

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Posted : 6th January 2018 7:42 am
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