Re: Servo or Stepper for Torch Height?
With a light Z axis stage, 5mm ballscrew and a direct drive 269 Oz NEMA 23 stepper, I am getting over 250 ipm using Mesa hardware and LinuxCNC. In tests with a dial indicator, I got the acceleration up to about 100 inches/sec/sec without loosing steps (0.25 G's). However, in the real world I got a few crashes due to missing steps. I think the short, sharp acceleration movements stressed the motor more than the 50mm movements I made in my testing so I had to back off a bit. It is clear that acceleration is a key LinuxCNC THC tuning variable and upwards travel (when the weight is on the drive) is when steps are lost.
So in answer to your question, yes a stepper can do the job but...
A little birdie told me that you might be using a 600 amp torch. If that is the case, your Z axis stage is probably quite a bit heavier than mine. I think that therefore the scales are tipped in favour of servos. I think this means that you will need a reduction drive. These are not hard to make if you have a lathe to make the shaft..This 3:1 design of mine works well for me and just bolts on where a NEMA 23 would and uses readily available bearing blocks. You might need 5:1 or better for a servo.
Rod Webster
www.vehiclemods.net.au