Problem- Aluminum Tubing Gantry

[martinrobt]

Has anyone ever made a gantry out of square aluminum tubing? I'm finishing up plans for a JGRO based machine and instead of MDF, I was wondering if 1/8" thick square aluminum tubing would be a better (lighter) choice. I'm accomplished at brazing so the joinery wouldn't be a problem. I just don't know if it would handle the stress. Would it be stiff enough.

Specs of machine.

Modified JGRO design
24" x 24" cutting area
200 oz steppers
1/2 10 ACME lead screws with Acetal nuts

Thanks

Robert

[skippy]

In order to get some answers it might be a good idea to tell everyone the size of the ali tube rather just the wall thickness.
Brazing aluminium tubing? huh?

[martinrobt]

I was thinking of 1.25" square tubing.

And yes, brazing. Although it can be a little tricky at first, brazing aluminum is actually fairly easy. One key to doing it well is not only use flux on the aluminum, but to preheat the brazing rod and dip it in flux as well.

Robert

[martinw]

Dear Robert,,

If you could post more details of the design that you are considering, it would be very helpful to everybody.

Best wishes,

Martin

[Don954]

So i came across a similar machine to the JGRO on another www, and was about to sit down a draw up my own vesion using a steel frame, replacable bed, and aluminum tubing gantry.... and just before starting today i decided to check if anyone had done it before lol, not only did i find the JGRO drawings completely done in solidworks! i also find someone else with aluminum gantry inspirations, whooda thunk it.. this interweb is amazing.

I plan on aimin for a 3'x4' size machine, with similar motor strength, and similar acme screw, with a welded steel tube frame base which MDF bed with bolt into (eventually like to get aluminum honeycomb bed and make vaccum table). Using similar size aluminum tubing for the gantry BUT i will likely make it two tubes up and across and down with trusses inbetween for ridigity. I find it extremely hard to beleive this will have stress issues but i will have a TIG welder.. (don't know the strength of brazed alum joinery). I beleive the week spots in my plan will be in the linear ball bearing slides.. and an ability to cut depth in the Zaxis. Routers usually only have about 2" of bit to plunge with and i want to be able to do some foam surfacing of greater depth... i may resort to making my own lower speed servo driven spindle that i can mount an end mill in but i fear this will be too pricey for my pocket book.

Anywho, keep in touch Robert, i'm interested to see how our parallel projects progress.

Cheers

Don

[martinrobt]

The base of the machine will be all JGRO, made from MDF, except for the size. It's the gantry I'm thinking about using aluminum tubing on. From the sound of it, it sounds just about the same as Don described.

Although I've never had a problem with a grazed joint failing, I guess there's a first time for everything. I just don't have a welder.

Don, thanks for the encouragement. Good luck to you. I'll check back in to see how you're doing.

Robert

[harryn]

I think you will be much more satisfied with 1/4 in thick Al sq tube. It is really handy to have Al thick enough that it can be tapped, and the difference in stiffness is dramatic.