Gantry supports, guides, and cam followers

[ydeardorff]

Hello all,

I am trying to work out a larger machine than most Ive read about thus far. Why you may ask, well. Im a retiring military man. My job in the military requires alot of design, mechanics, and engineering/fabrication. So this kind of project come fairly easily for me (at least in concept). This economy is not the best, and Id like the versatility to be able to do any sized project to help bring in money. Even including large glass panels, custom home entry doors, even custom automotive bodywork, pretty much anything using wood, foam, brass, and or aluminum.
So that being said Im looking at a workable surface of 4 x 8' with a Z axis of about 12 inches.
I have an early design for a home made auto tool changer, using a quick release chuck system, solenoid, and a 4th axis stepper for the rotisserie tool table.

My only real issue is how to support the guide rails, and acme screws over the length of the X and Y axis's, without droop or jiggling.

I have thought about using a C channel, and having the barrel nut ride inside it. I have also thought of the drawer slide rail setup, but welding the female ends of this together making for a very long slide.

I could use some fresh ideas here.

On the auto tool changer, I'm looking for a router that has a quick release chuck system on it. I can make the solenoid operated release system no problem, but having a tough time finding the router for this.
Im hoping to find one that will allow all of my bits to be preset, to allow for quick changing of tools, which will further open up my options.

Im looking at using Nema 34's with high torque values of around 1000 oz in for higher power, and better torque curves. Along with better handling of longer milling processes like doors etc. To help handle the heat build up.

The cam rollers I have found, seem like a really nice compact way to provide both support and a machined bearing to provide a nice clean linear sliding action. But ensuring the support slides are true to the table work surface, and the drive screws are properly supported to maintain accuracy over its length is turning out to be quite a trick to achieve.
And yes, Id like to find the cheapest option for this. Im not expecting .0001" accuracy, but good honest accuracy that is usable would be nice.

So, any fresh thoughts, new ideas, would be very appreciated. And yes, for those whom would ask,... I did use the search tool first.

[ger21]

Use rack and pinion and you don't have to worry about screws sagging and whipping.

And making a 12" Z axis to allow for foam cutting will seriously compromise the ability to cut harder materials.

for a large size machine, best to use a proven linear rail system. Take a look at the mechmate, www.mechmate.com. Uses fairly inexpensive Dual V rollers and home ground steel angle. Very solid, and about as cheap as you can get.

[lgalla]

I second the motion,linear that is.20/20 rack from Moore gear is about $90 for 12'
Mec Mate is a good design and the forum is a wealth of knowledge.
Larry