Rack Spur Motor Sizing help

[CPierce18]

I’m building a 5’x8’ CNC plasma cutting table and I’ve come to a stopping point. I’m not sure what size rack, gear, or stepper motor to purchase. The gantry itself will end up weighing close to 75lbs, and it rolls very easly over 2”sq. tubing for the X-axis rails. The gear rack will be tack welded to the underside of the tubing (gear rack & motor on both x-axis rails). I would prefer not to have a gear reduction for simplicity (K.I.S.S. – Keep It Simple Stupid). I’ve found internet sites and downloaded stepper sizing programs, but all they seem to be for is stepper’s with lead screws. Is there anything out there for motor sizing for Rack & spur gear? Next, any idea as to what side gear rack to use, and the spur gear for the motor?


How would I figure out these questions?

Here is what I have & need:

Frame Only: 280 LBS

X-axis Gantry Total: 75 LBS
Will be driven by (2) motors (one on each X-axis rail) by Rack & spur gear
-Need stepper motor sizes
-Need rack size/type/dp
-Need spur Size (not worried about a super-duper fine resolution since its plasma)

Y-Axis Total: 25 LBS
Will be driven by (1) motor by rack & spur gear
-Need motor size
-Will use same Rack & spur as X-axis

Z-Axis Total: 10 LBS
Will be driven by (1) 5/16” Threaded Rod Lead screw
-Need motor size

If everyone could give me enough info about all the calculations, I’ll just make a spreadsheet and post it back up here for everyone else to use also.

Thanks