We used to own a ShopBot which was a little to shaky to our liking, so I build a new gantry and y-car for it. Shared some pics at the ShopBot forum and soon other SB'ers were asking for copies of my plans. The whole thing snowballed from there and the plans were extended to cover a complete CNC router, a support forum was created, and folk are now building these MechMates all over the world. (Australia is the only continent still to get one running  )

The website, with forum and free plans are at http://www.mechmate.com/

Here are some machines:

Fabrica in Sri Lanka:

J.R. Hatcher, Wilmington, North Carolina :

This one rapids at over 1200 inches  per minute!

Doug Ford, Conway, Arkansas

Sean Reish, Orlando, Florida

John, Wiseton, Saskatchewan

Hugo, Pto. Ordaz, Venezuela

Kobus, Dalview, South Africa.

Greg, Hagerman, New Mexico

Ed Denton, Alamogordo, NM

Sharma, Rajasthan, India

David, Taibao, Taiwan

Thanks for the encouragement Dave.

Gravity does help but doesn't do it all. The motor pinions ride racks under the rails and the motors are spring-tensioned against the racks to pull the cars down and to eliminate backlash at the rack/pinion interface. The one side of the y-car that has no motor still has a spring and idler roller running under the rail.

There are now some videos at YouTube:
http://www.youtube.com/watch?v=hGVQQf_iQpI
http://www.youtube.com/watch?v=uGQ2J4GgXkg

And more (fresher) drawings at www.mechmate.com :
http://www.mechmate.com/forums/showthread.php?goto=newpost&t=376

Thanks Brett. I don't know of any MechMate being used for plasma, but then I know very little of what's happened to the 1200 sets of plans downloaded so far 

Thanks!

Thanks Benny

Everything is at www.mechmate.com

Your plain angle iron rails are what prompted me to post here today. By coincidence, I experimented with home grinding of rails this weekend. The story is here: http://www.mechmate.com/Forum/messages/11/3790.html

All the best
Gerald

Did you think this was a joke? 

The blue beast started about 2 years ago when we replaced the wobbly gantry on a ShopBot (see above Rafi's head in first pic). That worked rather well, so we built a second, longer gantry, and added a table and controller. Then got nagged for plans and a brandname was born for the download website. Don't quite know where this is going yet, but enjoying the ride so far!

(If truth be told, the major goal was to give our son a foot up in establishing his own business after school - that has worked really well.)

Edited to say that the post below does not apply to servo motors, and does not apply for stepper motors driven with coarse pulses

Maybe I can describe the resolution issue in practical end-result terms.... (and bring the thread back to table size)

If you are engraving the faces of medals and coins, you need a very fine resolution and lots of gearing (lots of pulses per inch).

If you are cutting background props for a Wild West movie set then you absolutely don't need any gearing!

Gearing is expensive, complicated. So, the natural question is, "How good can one cut without gearing?" I have lots of experience with a biggish (8'x4') router running 600 oz.in steppers directly to 1" diam pinions running on open racks. (The drives are 1/8 microstepping.) This combination makes a rather good machine for cutting up MDF and Plywood sheets with typically a 3/8" cutter.

When cutting rectangles out of boards (eg. kitchen cupboard doors), the "low" resolution of the direct motor/pinion/rack drive has no noticeable effect - the edges are smooth and free of chatter marks. When cutting curved counter tops, a tiny "chatter" can be seen on the edge - still far better than a jigsaw or bandsaw. These "chatters" are easily sanded out by hand. We do cutting on a job-shop basis and the boatbuilders and shopfitters have no problems with the edge quality. www.camcraftsa.com But we won't do small plastic parts for glossy promotional gifts. (A larger cutter also gives a much smoother finish). If you are willing to apply a little sandpaper afterwards, you can also do the high-gloss smaller artsy stuff

So, I guess what I want say is that one can build a productive CNC router with direct drive stepper motors, but this is for big cutters, big sheets of wood, big space, big income Anyway, this is a table size thread and I thought I needed to colour in the big table, low resolution end of the scale. The "tractor" end versus the "sports car" end - they both have their place, and they are not interchageable. You could drive to church on your tractor, but you can't plough a field with your sports car!

All the best
Gerald  (www.mechmate.com)