Aluminum extrusion as a straight-line ball slide

[Charlye]

Has anyone used aluminum as a carriage and base for a DIY ball slide? For very light duty it might hold up?

I've been looking at 3/4 travel drawer slides for a while.. the travel is pretty limited, typically 20 inches (just something cheap to get the CNC ball rolling). But why not make one's own slides using balls and 8020.

Just based on the diagram below for a given travel, the ball retainer could be
of equal in length to the travel, the carriage could be half, and the base sadly would be 3x. (Not quite to scale, I'll reduce the carriage width I think.)

The ball retainer could be made from a strip of UHMW-PE or something like that. It needs something to keep it from peeling back and freeing the balls when the carriage isn't overhead. I tried to solve that with screw down slides.

Another gotcha is that the carriage is going to 'stub is toes' on the balls as it slides into them. The carriage's ends could be ground a little wider.

Thanks!
Charlye

[Geof]

"For very light duty it might hold up?"

Sadly it would have to be very light duty. Aluminum is soft and a ball makes contact over a very small area; the aluminum would deform badly.

[Charlye]

It would deform, true. The initial wearing would be severe. Like a 'burn in' period. Grooves would form, after that it would probably be better. My application is light duty. Foam cutting and plotting, so that might not rule it out yet. How about using plastic balls instead of steel ball bearings? (Hard rubber balls?)

I looked around for steel extrustions. I didn't find anything off the shelf yet. $$$ custom shapes are possible, but that totally misses the point (cheap & accessible).

http://www.amerexprod.com/custshap.htm
Tolerances "Twist Tolerances 0.050 inch on section width over 4 inches. The transverse flatness tolerance is the maximum deviation from a reference base across any cross section flat surface. Allowable deviation from flat is.010" per inch of width."

Are the tolerances on aluminum extrusions any better than steel? (I would think so).

Charlye

[mtd091571]

Hi, I tried what you were saying a while back and had pretty bad results with it. The problem is I had to had the balls tight enough against the extrusion to eliminate play in the axis. After a couple of passes with no loaded on it, the extrusions got chewed up by the balls. I had thought to by 8020's linear bearing pad that they sell by the inch. You could route a concave with a endmill to match the size of the ball bearings you would be using and then attach that to the uhmw pad to the groove in the extrusion. I have'nt tried it, but it seems to be the next step I may take.

[Al_The_Man]

I have used this principal http://www.itemamerica.com/outside_catalog.asp for linear slide along an extrusion, I used the chrome steel rod top and bottom on the extrusion and also they supply matching roller sets to make up a travelling axis carrier.
One neat feature of some of the Item extrusions is they have galleries through the extrusion to pipe oxygen & gas to tap off for cutting torches etc.
( The item site go to Dynamic elements, Linear Slides, Shafts)
Al.

[mtd091571]

Do you happen to know the price range on those rollers? I was looking at the 10mm. Nice Stuff.

[Charlye]

Al, Nice find.

The "Shaft Clamp Profiles" are a novel means of holding ground rods. It's a great way to avoid drilling the rod. For short lenghts.. one might be able to just clamp the rod at the ends, instead of the entire length.

Dynamic Elements / Linear Slides / Ball-Bearing Guide Bushes / Shaft-Clamping Bushes
http://catalog.item-international.co...3AIN_%23V1.jpg

I love this idea. A self-lubricating bushing held inside the main cavity of the extrustion (eg 2020,3030,5050) using a single grub screw. So simple.

mtd091571

After a couple of passes with no loaded on it, the extrusions got chewed up by the balls.

That's too bad. I was really hoping it would work.

Thanks. Any thoughts on plastic ball idea?
Charlye