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View Full Version : Building a gantry CNC table



ibewgypsie
02-10-2004, 09:16 PM
ANy Suggestions?

I had a small gantry that worked by sliding uhmw in UNI-strut cases, was xl gear belt driven with flat belt riveted to it. It basically ruined the dremel I had mounted in it. the bearings were shot.

This time, 5 feet by 8'4" I have both a router and a plasma cutter ready. I plan on chain drive, skateboard wheels running the center of angle. Rutex drives, opto relays to turn things on and off. 2-Gearboxes are 50:1 ratio with 200 ppr encoders. On a 1 7/32" sprocket diameter that should give me plenty of resolution.

ANY suggestions? This is the third or fourth I have worked on, the first two were failures because of mechanical design. (bent housings and uhmw sliders with screw drive.)

My cnc mill works great, but that was a modified proven design. I plan on using the turbocnc software again.

wierdscience
02-10-2004, 10:04 PM
Well as you know I have been kicking the idea around myself.

I helped design one gantry using linear rod,but instead of using large diameter or support rails I took and threaded the ends of the rods(they were 3/4" od) and used nuts to crank up tension like a quitar string,two rods 6" apart and 9' long were able to support 300 lbs with no deflection,pretty good I think.

I also have a few 1" linear bearing pillow blocks you can have real cheap,let me know.

I have also taken 1/2-20 allen cap screws and turned the od of the heads for a press fit to hold ball bearings(6203-2rs I think it was)two of these crossed on a angle bracket make a jamb up slide bearing.

E-mail me,I like this sort of stuff!

ibewgypsie
02-10-2004, 10:36 PM
I'll do better, I can post pictures.

How do the bearings mount? I got a plan, got about 20 feet of 1" shafting too. email me if you will...

I just got, 200 opto modules, 60 opto-22 racks. They work perfect with parallel ports. Not all are positive logic thou. AND.. 2 2hp dc drives and a electronic speed loop controller. *going on my bridgeport head VFD*.. whoo hoo what a night.. but I lost 4 other auctions for controls tonight.

For a small stepper system, you can use the opto modules, 4 bits for the motor (or a ul2003 chip and two bits of logic), and use resistors to limit current. Put together a whole system for less then $30 for the drives. I have built three like drives. NOT for production use thou. the motors heat up.

David