Belts to replace long ball screws? What are your thoughts??

[runinbymdnt]

I just returned from the Design and Manufacturing trade show here in Southern California.

I saw several examples of belts used for moving things in place of ballscrews. The one I was most interested in was a stainless steel strap with percision holes in it. It ran on plastic pullys with screw heads that corrisponded with the percision holes in the steel belt. The salesman told me it would hold .003" in a foot.

It was much more affordable than the rolled ballscrews I need for my machine.(y is 74" long and x is 63" long)

I would like to hear your thoughts.
Any infor on belts used for this purpose would be of interest to me.

As allways, thanks.

[holbieone]

i think it would be fine on a machine like a plasma cutter or water jet ,but on a router i would think it would flex and the tool would lag

[runinbymdnt]

So you think with the pullys that the belt runs on firmly mounted, this stainless steel strap, the belt, would flex, or stretch?

The salesman at the tradeshow didnt think so. Salesmen dont bs the buying public at a trade show, do they?

[Zumba]

Sounds like a pretty crappy system to me. Good for no-cutting-force systems like laser, plasma, and waterjet. No good for routers or mills.

The fact is, there's no such thing as super steel. Steel has a modulus of elasticity of around 30,000ksi. That salesman would like to believe that his super stainless stuff has a modulus of 30 trillion psi. He'd also like to empty your wallet.

Whether he likes it it not, the steel band WILL stretch... a lot... There really is no advantage of a steel band over a standard neoprene/fiberglass belt. In fact, the only thing it brings to the shop is a sharp edge that will cut you if you accidently move your hand over it. If you want to save money, go with R&P.

I'd be quite amused if that company patented the design. The patent would be worthless because they're copying old-skool, dot-matrix, printer paper feed mechanism technology. Remember the good old days where paper had holes on the side?

[runinbymdnt]

Thanks Guys for saving my wallet. Once again this forum provides good information.

I guess its back to rolled ball screws.$$

I really apreciate the help. Its like you guys are just down the street, ready to stop by and give me a hand. (However not a single one of you has showed up at my shop and said let me do that for you. Darn )

Thanks again.

[holbieone]

rack and pinion is a cheep way to go

and if your software allows you to map out the axis you can probably hold some good tolerances

and if it doesn't for a router it will still hold a reasonable tolerance

[smilewizard]

Another option is a chain drive with spring tensioning. I recently changed my system from a belt drive to a chain system. You can see a KISS approach under "4 x 8 Plasma table plans"

Andrew

[runinbymdnt]

Originally Posted by holbieone rack and pinion is a cheep way to go and if your software allows you to map out the axis you can probably hold some good tolerances and if it doesn't for a router it will still hold a reasonable tolerance

Can you explain what "map out the axis" means?

[holbieone]

Originally Posted by runinbymdnt Can you explain what "map out the axis" means?

well you move an axis a set distance then you measure that distance

in some controllers there's a table where you put in the location from the home position and the difference from the actual move and the programmed move

you do this through out your full axis range so when you move 12 inches it is really 12 inches

for example :all ball screws have lead error to some degree

lets say it's .003 per foot ,for every foot you travel you get accumulative error (in two feet your move would be off by .006)

if you map this out the controller will adjust for the error as the axis moves

[greybeard]

I find it interesting that no one has asked what your load is.
If you were moving a 300lb gantry over that table size, your requirements would be somewhat different to moving a laser mirror.
Just my groat's worth.
John

[runinbymdnt]

Originally Posted by greybeard I find it interesting that no one has asked what your load is. If you were moving a 300lb gantry over that table size, your requirements would be somewhat different to moving a laser mirror. Just my groat's worth. John

That question has now been asked. My gantry is constructed of mostly 1" thick cast aluminum tooling plate, plus cars, rails, screws, the x axis trolly, the z axis, and the router. I only have an estimate, but I bet its 250 lbs at least.

So how would that change things?

[greybeard]

runinbymdnt - in your case probably doesn't change what has been said.
In my case where I'm only moving a 24" x 8" x 3/4" piece of wood (there isn't even a table) the punched steel tape that I intend to use for the x axis is perfectly adequate for the size, speed and accuracy of what I intend to do.

Regards
John