[mb198007]

OK here goes. I have and idea for a CNC router using a 2-1/2 hp router. Cutting area X=32" Y=20" Z=6". I have 2 ea hardened to RC60 1-1/4" rods with thompson linear ball bearings for the X axis I plan to use the rods unsupported in the middle and anchored on the ends. I plan to use 3/4" hardened steel rods for the Y axis with Thompson linear ball bearings. I will use 1/2" hardened steel rods for the Z axis with Thompson linear bearings. I have a good source for new Thompson bearings. I was going to use 1/2" aluminum plate for the movable gantry sides. Plan on using 5/8" ball screws for all drives. I cannot decide on stepper motors, 269ozin or 640ozin both with Gecko drives. Please let me know what you think. My main concern is will the X axis be rigid enough W/O support in the middle. I plan to put 4 bearings on the gantry (2 per side) on a 12" wide gantry.

[ger21]

To get a 32" cutting area, you'll probably need at least 44" of unsupported length. This will most likely have some deflection. But, you may be able to eliminate most of it by double clamping the ends a few inches apart. You'd probably need 50" shafts or longer, though. If you're spending the money on Gecko's, go with the bigger motors.

[mb198007]

Thanks for the info. I will use the 640 steppers from Homeshop CNC. Which Gecko drive to go with? Is there a big advantage to the 210 over the 201 for a router of this size. I will use .750" lead screws with a .200 lead on the X & Y. What will the 210 get me??

[ger21]

What will the 210 get me??

Absolutely nothing. The G201 and G210 are identical. The G210 just has an additional step multiplier on it. You would only need the step multiplier if your computer can't output steps fast enough. Mach2 can output 25,000 steps per second on a 500Mhz computer, which will get you about 150ipm. With a faster computer, you can get up to 45,000 steps per second from Mach2, which will give you up to 270ipm, if your steppers have enough torque at 1350rpm. Instead of a G210, you might want to look into a higher lead screw, between .25 and .5.

[mb198007]

Thanks for the info.