Ball screw, threaded rod, chain, belt, or rack&pinion drive?

Design of moving parts, and method of locomotion.
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DonJohn
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Joined: Sun Dec 12, 2010 6:53 pm

Re: Ball screw, threaded rod, chain, belt, or rack&pinion dr

Postby DonJohn » Thu Dec 30, 2010 2:06 pm

Hi, i did some sketchup to clarifie and illustrate my thought.

One colour is one component. So the threaded rod (gray) is stationary and motor(black belt) turns nut (green) around the rod and since nut is fixed to gantry (orange) with bearing (green and orange connecting place) gantry moves with the nut.
rod1.jpg

rod2.jpg


If one could get hands on a pipe that has threads inside and out then it would be quite easy to build. Just need some bigger bearings (downside is that these cost more). Up side is that this rod could be quite long. I would say that basic principle resembles rack and pinion

hope this helped
I'm not a native English speaker so please beer with me

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larry104
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Joined: Wed Dec 08, 2010 1:29 am
Location: Bay Area

Re: Ball screw, threaded rod, chain, belt, or rack&pinion dr

Postby larry104 » Thu Dec 30, 2010 5:15 pm

Yes, that helps a lot. The downsides I see:
- you need two of these on each side of the gantry
- the assembly might be a little tricky since you need to slide in the gantry before you can mount the rods
- the bigger bearings as you mentioned
- getting the threaded pipe (inside/outside)

The advantages would be:
- a single motor in the middle of the gantry
- enables us to use longer rods

Did I miss anything?

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Awesomeness
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Re: Ball screw, threaded rod, chain, belt, or rack&pinion dr

Postby Awesomeness » Mon Jan 03, 2011 8:22 am

I think it's a pretty clever idea. I'm sort of on the fence about whether it has a place in this machine design, mostly because it is so untested. I'm definitely not discounting it though. What do you guys think?

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DonJohn
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Re: Ball screw, threaded rod, chain, belt, or rack&pinion dr

Postby DonJohn » Tue Jan 04, 2011 10:35 pm

If one would have to choose between belt and chain (basic setup for both is the same), my current view on the matter is that with belt the main problem is stretching (due to the elasticity), and with chain sagging (due to the weight of chain).

Elasticity problem can be removed as shown on Beermkr's link
http://www.youtube.com/watch?v=OdJoVh6D ... re=related using two opposite belts.
Could sagging in chain be removed just by supporting the whole belt with board, aluminium bar or something like that?
I'm not a native English speaker so please beer with me

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larry104
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Location: Bay Area

Re: Ball screw, threaded rod, chain, belt, or rack&pinion dr

Postby larry104 » Sat Jan 08, 2011 1:48 am


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Awesomeness
Posts: 107
Joined: Thu Dec 02, 2010 7:29 am
Own CNC?: Yes
Location: Colorado
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Re: Ball screw, threaded rod, chain, belt, or rack&pinion dr

Postby Awesomeness » Thu Jan 13, 2011 10:13 pm



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