I have designed in Autodesk Inventor and am in the process of building a CNC router, 4x8ft, steel frame, MIC-6 plates. I'll be using steppers driving a pinion on a rack for the X&Y axis, a screw for the Z. Pretty typical stuff.

Power available is 220V 1-ph @30A, maybe 50A depending but enough either way.
The table is 2x4x3/16" tube, 2x3x1/8" cross supports
The gantry is MIC-6 risers, welded steel cross tubes.
Total gantry Mass to be moved by the two X steppers is 225#
Hiwin 20 series rail and bearings throughout, medium preload, 12" bearing spacing
20 pitch, 20 degree racks, driven by a 1" P.D. spur from a timing pulley / belt reduction of undecided ratio.

I plan to cut:
Wood: 1" MDF, 3/4" oak solid and plywood, 3/4" solid pine and plywood, maybe some exotics
Plastic: 1/4" polycarbonate, 1/4" acrylic and several lighter plastics, maybe PE
Metal: 6061 / MIC-6 aluminum, brass
Other: 3mm / 6mm foam for the RC airplane hobby (possibly cut with a hot knife/pin)

All materials I expect will be cut at 60ipm max, the foam maybe 100ipm. I'm estimating 75# max cutter force.
I'd be nice to traverse the table in 30 seconds or 180ipm no load.

I'll start with a 3/4hp router motor later upgrading to a spindle, which means cutting metal will come later.

I have an older 800MHz PC running WinXP dedicated to the job with USB, serial and a parallel port. I can build another computer if needed.
I also have a 48VDC 40A power supply I could use.


OK. I calculate with orientalmotor.com the X axis will require 625oz-in at 59rpm, 2.0 safety factor to make the cutting specs at 75% efficiency. Therefore each X axis stepper theoretically will need to make 312oz-in torque.
I'd use the same stepper for the Y and Z which should work nicely.

Yes the frame is heavy, it is also ridiculous rigid and once complete should be a workhorse. I have work lined up for it now and for the foreseeable future.



Now for the most asked question which I have spent a great deal of time trying to figure out.
Which steppers and drives?

I'd like to use KL34H295-43-8B, NEMA 34 MOTOR 906 oz-in. Torque falls fairly propertional with the speed. The chart doesn't mention voltage.
142oz-in per motor @ 3000ppm half step which is 470ipm using a 1:3 ratio.
460oz-in per motor @ 400ppm half step is 60ipm max cut speed per motor.

That's a huge amount of torque

I'm in love with the NEMA 34 motors and that above is way too much torque so:
KL34H280-45-8B might be a better choice at 640oz-in. Unfortunately I can't find a torque curve.


If you're still reading. Any suggestions? Do you see any obvious errors in my logic? I'm looking for stepper torque curves now. Any suggestions will be welcome.
What is a reasonable maximum pps at 48V with motors in this range?

I'm considering the KL-9082 driver here: http://www.kelinginc.net/KL-9082.pdf

The long story short, I have some money to build this finally so I don't want to cheap out on parts to regret it later. The motors and drives are the last things to figure out.

Thank you,