Re: [CAD_CAM_EDM_DRO] Servo Drives

A&K ERWOOD wrote:

> G'Day All,
> I am looking at buying three servo amps for a milling machine
> retrofit, 1 motor is rated 92VDC 24amps at stall the other 2
> motors are 92VDC 10amps at stall. The amps I am looking at buying are
> BALDOR amps and they accept both step and direction pulses,
> or a + -10v signal. Which of these input types is best??? Why???

Well, the motors sound plenty powerful, if they are designed for fairly
low speed,
that is a plus, as you don't need high belt step down ratios. 92 Volts
at 2000 RPM
or so would be real good with a 2:1 step down ratio.

Do you already have ballscrews with anti-backlash nuts on the machine?
To get the best performance, these are pretty necessary.

With both step & direction as well as analog servo, you have a wide
range
of options for the control computer and CNC program.

Going the full servo route, with DC tachs if the servo amps need them
(may be
included in the motors) and shaft encoders directly driven from the lead
screw
is probably the most accurate and reliable system within reasonable
cost.
You can get much higher resolution at less cost with a shaft encoder
than
with a linear encoder. I have 1000 cycle/rev encoders, that give 4000
quadrature
counts per rev, on a 5 TPI screw, so that generates 20,000 counts per
inch,
or a count resolution of .00005". I am using the EMC program with a
Servo-to-Go card for the analog output and encoder counters.

Jon