Re: [CAD_CAM_EDM_DRO] Servo/Stepper on a Surface Grinder

Hi Alan:
I have a couple of comments and questions:
First, if you intend to retain the rack drive on the long axis (X??) it
should be simple to isolate the motor completely from the machine, by adding
a toothed belt sprocket to the handwheel shaft and a splined sprocket to the
driving side with a fork to slide the driving sprocket in Y so it remains
aligned with the driven sprocket.
This allows you to choose any motor within reason as your X axis drive.
It also isolates the drive from a lot of the cogging you're concerned about
and allows you to choose a useable table speed easily while remaining in the
proper power band for whatever motor you choose.
You will only suffer from motor mass if you attach it to the grinder table
and use it to drive a screw.
I think that's a poor idea for two reasons.
First, you need a very coarse pitch ballscrew to make this work at all ;
second, it either needs to be PERFECTLY aligned or have a floating mechanism
in the nut to accommodate whip.
If you neglect this, you,ll have unacceptable humping of the table at high
screw speeds.
My big grinder uses a floating hydraulic cylinder to move the table...simple
and effective, but noisy, and a nightmare to retrofit to a manual grinder.
Not only that, you've got a horrendous high-mass load reversal issue at a
high speed and repetition rate...this just screams to me to "Build it strong
like bull", but as you point out, there's not much meat on the table to
attach it to.
All the electronic bafflegab I can't help with at all!!!
Cheers

Marcus