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Designing a backlash-free drive with a worm screw.

BeitragVerfasst: 30 Dez 2018, 20:16
von fotoopa
Designing a backlash-free drive with a worm screw. To eliminate the backlash, 2 worm screws are required that have a small shift. With only 1 worm screw you have about 0.6mm of backlash which is a lot.
A custom housing now contains 2 worm screws at the right distance. These can easily be mounted on the standard base plate 120x60mm. In the setup I use shafts of 500mm length. To increase stability another 4 small support wheels are added that run on a flat surface. This way the carriage can not tilt and remains very stable. With an XM-motor and a gear reduction of 3 times the drive goes quite smoothly. At the end I made a worm screw stop (yellow plug). Also the gear of 30T contains an adjustment for the worm screw. In the foreground of the picture you see the details of the housing. I also made a quadrature decoder with home point with a ball bearing D8x4x3mm With an encoder disc with 15 neodymium magnets you get 60 pulses per tour or 0.0785 mm per pulse.

All files on Thingiverse: https://www.thingiverse.com/thing:3323197

A few pictures:
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HD: https://www.flickr.com/photos/fotoopa_hs/31587974067

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HD: https://www.flickr.com/photos/fotoopa_hs/31587973697

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HD: https://www.flickr.com/photos/fotoopa_hs/31587973327

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HD: https://www.flickr.com/photos/fotoopa_hs/32654940448

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HD: https://www.flickr.com/photos/fotoopa_hs/32654940218

Frans.

Re: Designing a backlash-free drive with a worm screw.

BeitragVerfasst: 31 Dez 2018, 10:38
von steffalk
Hello Frans,

afaik, two worm screws put directly behind another and one turned 90° gives a fine result also. So you can just fix the two work screws with, say, a single BS30.

Best Regards,
Stefan

Re: Designing a backlash-free drive with a worm screw.

BeitragVerfasst: 31 Dez 2018, 11:25
von fotoopa
Thanks Stefan,
I've tested it now and it's going pretty well. That's easier. However, the amount of backlash depends a little on the position of both nuts. Best suited for normal use.
The 3D block is slightly more robust as a whole.

Well, there are still some other blocks left, like the worm stop and the worm gears. I ordered 10 pieces D4x500mm shaft together with 50 worm pieces FI-37926 to make all kinds of transmissions.
I have to fill my days with all kinds of tests and sometimes the solutions are much simpler than I thought.

Update:
My 3D print version has better support because both worm nuts are at a slightly greater distance (31.5 center to center instead of 15mm). This makes the backlash more constant and the shaft is more stable. If you also use a distance of 30mm and twist the worm screw 90 degrees there is hardly any difference.

Frans