4 x 8 2006 Joe, Anyone?

[deanbrock]

If someone's already asked this, my appoligies, I've not been able to find it.

I'm finally finishing up with my JGRO, and planning my next machine.

I've read somewhere Joe (I beleive) mentioned stretching the width of his 2006 to an even 4 foot, and using two motors to push the gantry around(similar to the 4X4 hybrid machine). I like the idea.

Along the long length, obviously you could run 8 foot easy, as long as the machine is on a well built table. The weak point, in my best guess, would be the gantry sagging in the middle of the 4 foot run. But the design looks more than stout enough to handle it.

Does anyone see any obvious pitfalls here assuming moderate to low feed rates? Has anybody tried this?

Thanks,
Dean in Knoxville, TN

[joecnc2006]

no, to be able to do 8' you can not use acme rods, just the weight of the rods will cause them to sag. On my 4x4 now i am pushing the length of the rods to their max.

Joe

[deanbrock]

Yeah. Good point, I hadn't considered that.

Well here's a what if.

1 inch black pipe, with it's coating measures in at 1.30 inches, I'm thinking a 1 3/8 - 6 die would cut workable threads but still leave enough metal for support. Maybe. Does anyone know how deep a 1 3/8 - 6 thread is?

This would be lighter than a solid bar lead screw, and perhaps wouldn't sag as much.

But this begs a more fundamental question which I have no experience with. Would a 20 foot long inch thick pipe supported at both ends have more or less sag than a 20 foot long, inch thick solid bar?

Thanks,
Dean

[joecnc2006]

you would only have a little more than 1/8" wall thickness to provide threading and support.

Joe

[ger21]

Originally Posted by joecnc2006 no, to be able to do 8' you can not use acme rods, just the weight of the rods will cause them to sag. On my 4x4 now i am pushing the length of the rods to their max. Joe

I personally wouldn't try to build a suspended 8ft table, but you can use bigger acme, 3/4" or 1" diameter would probably be OK. But you'll need more power to accelerate the heavier screws.

[bp092]

If you're going for a 4x8 machine I'm assuming its for more commercial (not hobby) purposes. I wouldn't reccomend going with the more DIY smaller end pipe design, especially not the leadscrews as joe said they will flex. The 4x4 really is the absolute max. And as Ger said if you used bigger ball screws ($$$) you will need more power, and stronger motors ($$$). And you're going to spend $$$ I wouldn't go half way, I would just build a metal R&P machine such as the Mechmate.