Re: [CAD_CAM_EDM_DRO] Converting Hydrolic copy Milling Machine

Harko Schwartz wrote:

>I think it is a worthwhile thing to convert. You need to have position
>feedback which can be done with a tape scale and you can get hydrolic servo
>valves that can control the motion.
>

have you priced proportional hydraulic valves? They are REALLY expensive,
like thousands of $ each!

> You will need to have a CNC that is
>capable of doing Analog out like the Machinemate CNC.
>
>

It gets much more complicated than that. You need a valve driver that
adds dither to the output. at several hundred Hz, to keep the valve spools
floating on a cushion of oil. if you just drive the valve with the plain
PID output, the stiction of the servo valve will cause the machine to
have terrible servo hunting problems. It is possible that at a 1 KHz
update rate, the dither could be added in software, at either 333 or 500
Hz. But, you still need the servo valve, and a valve driver amplifier.

Jon