Wire Rope instead of belts / ballscrews

[appicnc]

Hello from Downunder Group

I am designing my second machine ( about 2.7m by 1.5m by .3m ) the first used acme screws and had " issues " with speed, not a problem when cutting, but when doing rapid moves on a bed that is more than twice the size would be.

I was going to use toothed belts but have recently build a winch to lift a friends model railroad into his garage roof, this got me to thinking of stainless steel wire rope, say 3 - 4 turns around a driven drum the a loop to drive the axis.

I have done a google search and drew a blank, any ideas??

I was thinking of doing a mockup of one axis and seeing how much force was required before the wire slipped on the drum.

Don't hold your breath but I will report back to the group, for large routers it may be a way to go.

Ed

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[daedalus]

We use cable drives in some of the robots at work, they are fine for short distances, but over 3m i would think cable elasticity would be an issue. There have been other posts on cnczone about doing cable drives, try searching in the linear motion subsection (i think it was there).

[jcc3inc]

Sir,

Because of the elasticity if the cable, if you use some sort of good position feedback, you should be able to make it work. However this adds some complexity. (and cost)

An alternative would be to use gear rack and pinion- no elasticity, and it is easy to implement. You can buy 6 foot 1/2 x 1/2 gear rack, 20 DP, 20 degree pressure angle from Standard Steel Specialty Co, www.stdsteel.com/gear.htm
Cost is about $23 each in qty = (2). For a drive pinion, you should have at least 18 teeth with more teeth desireable. You will have no trouble with rapid traverse either!

Regards,
Jack C.

[appicnc]

[Cost is about $23 each in qty = (2). For a drive pinion, you should have at least 18 teeth with more teeth desireable. You will have no trouble with rapid traverse either!

Regards,
Jack C.[/QUOTE]


Hello Jack C

I had thought of rack and pinion but was concerned about the problems of getting the rack here, Australian distributors use linear bearings ect. as a way of paying off their home loans, holidays and cars with each purchase, I will see what the longest length I can get them shipped here is.

Thanks for your suggestion.

Ed Pinder

[appicnc]

[Cost is about $23 each in qty = (2). For a drive pinion, you should have at least 18 teeth with more teeth desireable. You will have no trouble with rapid traverse either!

Regards,
Jack C.

Hello Jack C

I have sent SSS a quote request for racks and pinions, I will need to have then in joinable lengths but I'm guessing that won't be a problem.

Thanks for your advice I'll let you know what happens.

Ed Pinder

[appicnc]

Sir,

Because of the elasticity if the cable, if you use some sort of good position feedback, you should be able to make it work. However this adds some complexity. (and cost)

An alternative would be to use gear rack and pinion- no elasticity, and it is easy to implement. You can buy 6 foot 1/2 x 1/2 gear rack, 20 DP, 20 degree pressure angle from Standard Steel Specialty Co, www.stdsteel.com/gear.htm
Cost is about $23 each in qty = (2). For a drive pinion, you should have at least 18 teeth with more teeth desireable. You will have no trouble with rapid traverse either!

Regards,
Jack C.

Hello Jack

I have had a quote from SSS, they don't make / sell the pinions, can you suggest an alternate supplier and or a pinion supplier?

Thanks

Ed Pinder

[jcc3inc]

Here's a source of 20 DP, 20 degree PA gears:

Boston Gear:
#YA20, 20 tooth steel, 1/2 bore, .500 face width, hub projects .44
#YA24, 24T steel, 1/2 bore, .500 face, hub proj .44

Regards,
Jack C.

PS:

Martin Gear and Sprocket is another source:
TS2020 is 20T similar to above
TS2024 is 24T

JC.

[Monster]

The first Shopbot www.shopbottools.com used a wire system. Why don't you email them and ask them about there experiances? They are realy help guys and I am sure they will be happy to respond.

Jeff

[Greolt]

.............................. can you suggest an alternate supplier and or a pinion supplier?

Ed are you still there?

TEA in Qld has rack and pinions. http://www.tea.net.au/welcome.aspx?page=19

Best source I found in Aus. Their rack is Chiaravalli . Italian.

Use "Module 1" and about 24 tooth pinions. Gear it down 4 to 1 with timing belt and pulleys.

Depending on what drivers you use you'll get about 15000mm/min and 100 steps/mm

It'll work great. Very good drive mechanism for a large router.

Greg

[Islam]

This is my own new design of a cnc plasma cutting machine depends on the wire rope and threaded pulleys which give high precision accuracy and very long life time.

http://www.cnczone.com/forums/plasma...an-plasma.html

[BobVanDyke]

I worked for a company several years ago that made a small gantry robot using cables, pulleys etc. They used aircraft cable around nylon pulleys with bearings pressed inside. I believe it was modeled after a plotter. If you use a cable you will need to look up the cables minimum bending radius. This will determine the minimum size pulleys you will need. The drum will also meed to exceed the minimum bending radius. Our drum was grooved to fit the radius of the cable. The cable was put through a hole in the center of the drum and wound around the grove on both sides. As the drum rotated the wire would spool in on one side and out on the other. I doubt this would work well on a very large machine. All the cables were set to the proper tension to compensate for the stretching of the cable. Finally they programmed a look up table for every one inch movement so the computer could correct for errors. After programming the robot was good to .001 inch. These were small machines for gluing surface mound devices to circuit boards.

I like the rack and pinion idea. Simpler, straight forward, and many fewer parts. Then again I don't have any experience with rack and pinion systems.