Z lead screw nut thread stripped

Ray

I used the new style nut trap STL and just cut a cube out of it to accommodate the new Z nut.

John

Thanks John,

I can mill some stock that'll fit that (but all my hex stock is imperial, which has stopped me doing it so far) - what did you use to edit the stl by the way? I haven't managed to find anything that lets me ...

Cheers

Ray

Ray
I use a package called TurboCad. I bought it originally to use with my CNC machine, mostly 2D work. But it also works fine with 3D objects and will import STL files and modify them.. I milled the brass down to 10x10x15 mm

John

Blender can also import STL files:

File->Import->STL

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RS-Online Ormerod #263, Kossel mini with Minitronics, Prusa i3 MK2

Thanks for the pointers johneato and 3D-ES,

Ray

thanks again johneato - I printed out your edited stl and found it's a snug fit for the flats of my 3/8" hex brass bar stock, so I tapped a chunk of that and it's all working great (I had to snap off the remaining bit of black acrylic that had been the nut trap on my machine, it may not have held on much longer judging by the ease with which it came away, so quite a timely mod)

cheers

Ray

Ray
Pleased to hear I was of some use to someone, the help has been mainly incoming so far.
I found the black acrylic had already broken on mine when I dismantled the z nut trap so that was another reason to replace it.
John

HI guys, just assembled my new "Green" Ormerod. Found out same problem, since first run Z screw was wobbling, due to Z gear tilting on the bearing. Just the time to print a couple of snowmans, the coat hook and the two sets of XYZ samples for compensation that I found out a lot of grinded metal powder all around. Unmounted all, cleaned, polished the screw with fine grinding paper. I found out too much play between gear and beating and some "bumps" inside it. I removed bumps on the bottom bearing shoulder in the gear, applied a turn of electrical insulating tape on the bearing and a small amount of MoS2 grease on the screw. Now it turns smoothly and quiely with very little woobling at the top. Get back to print, will you keep informed. Perhaps I will apply a longher bronze (not brass) nut, but I nedd to ask some colleagues in the factory to build it on a turning and milling machine.

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Green Ormerod Fan

Improvements and tunings:
- aluminum bed with spring suspended bed and iamburny's Y belt tensioner
- masonstonehenge's spring loaded extruder with dc42's herringbone gears based on iamburny's design
- philiptemobster's extruder holder
- Abs made fan holder, X carriage and extruder
- 0.78 firmware
- dc42's IR sensor + led PCB
Tested and want to improve:
- laser cutting L-Cheapo attachement
WTD:
- double extruder (to use different support material)

I solved my z-screw wobble with the second replacement z-driven gear I printed. This time used a vice instead of a hammer to get the nut in the gear. I also replaced the threaded rod by a hardened steel one, and used a brass nut in the z-nut trap instead of a steel nut. And of course applied some light machine oil.

Edited 1 time(s). Last edit at 01/27/2014 04:54AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I found this M5 coupling on Ebay. I think its a HUCO coupling insert. The nut part is too large to fit the nut trap but I found that the serrated part fits without turning. See pic
(This is in the original "Special edition Ormerod" z nut trap on the acrylic x-rib). I also replaced the M5 rod with stainless steel and the action is silky smooth. I dont know if I quite trust the fit as shown, but if it shows signs of slipping then I will try to make a custom z nut trap which uses a clamp so that the coupling can be clamped firmly in position by the serrated part ( while allowing a bit of rotation around x and y for the wonky gears!) so removing any slop.

Feels good but not tested in anger yet!

ergards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

I'm not sure I would want to clamp the nut. If something goes wrong and the machine tries to drive the print head down into the bed, currently the z-nut comes out of the bottom of the nut trap and no damage is done. This has happened several times to me, e.g. when the IR sensor wires have come off.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

While I'm still busy looking for brass nut locally, ( but without luck yet ) my Z axis really noisy even I already replaced a new spare nut. ( my ormerod only printed 600gm of filaments so far )
I have some 623 ( 1033zz actually , its the same size ) bearings laid in my drawer for years, those are Japanese bearing. after I replace it, my Z axis become quiet and stable again.
Anyone of you have bearings problem yet? or just me ?

Quote
dc42
I'm not sure I would want to clamp the nut. If something goes wrong and the machine tries to drive the print head down into the bed, currently the z-nut comes out of the bottom of the nut trap and no damage is done. This has happened several times to me, e.g. when the IR sensor wires have come off.

Good point! I will bear it in mind if I have to redesign it.


regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Quote
dc42
I solved my z-screw wobble with the second replacement z-driven gear I printed.....

Great, but this design is so mechanically wrong, there is no reason at all to put strain on the z-screw and make it wobble - z-gear, z-driven gear and bearing should of cause be in the same horizontal level

Raise the bearing as needed, about 6mm as far as I remember, redesign the z-driven gear with a deeper hole, aka get the bearing in the center of the z-driven gear

Erik

I have found the cause of the wobble, at least on my printer. It is simply that the nut does not fit square on the threaded stud. Remove the screw nut assembly and If you rotate it between you fingers you will see the nut is not square with the screw. I tried with a longer nut and it wasn't square either. The problem is the quality of the nut and/or the quality of the screw. I suspect top quality nut and stud will solve this if you can find one...

Oh for a cnc machine.......
I would like one, but I think I'll save you for a cnc laser cutter first...