RE: [CAD_CAM_EDM_DRO] Re: USB and ncPOD system

>
> >What most users of fractional hp lathe spindles don't
> realize is that
> >steppers can't keep up with the needed feedrates to accomplish
> >effective metal cutting during threading.
>
> That's a blatantly misleading generalisation.
>
> My stepper driven Z axis can move at 90 ipm if required, most of my
> threading is done at 500-1100 rpm and I've not had it "fail
> to keep up"
> yet...
>
> Steve Blackmore
> --
>

Hi

Just popped out to the shop to check my ELS. At 1180RPM which is the
fastest the Gingery Lathe can run, I can do 8 TPI before the ELS tells
me that my spindle speed is too fast for what it can generate for step
rates.

That's based on a 10 TPI lead screw, 1:1 coupling and 10 micro-steps per
step. The ELS is running about 23kHz pulse clock so maximum step rate
is 23kHz. Were I to change to 8 micro-steps per step or 4 micro-steps
per step I could easily do 5 TPI. Were I to change to a TI DSP that
does 150MHz and has 32 bit math operations I could run a 50Khz pulse
clock and easily do even faster stepping rates. Were I to change to an
300MHz ARM module or 1GHz Pentium card I could do even faster. But it
would all cost far more than the $120 or so for the basic ELS without
stepper driver.

At the moment I'm very pleased with the Ohmikron modules as stepper
drivers which have worked very well. I believe we're still having noise
problems with GECKOs.

John Dammeyer