SV: [CAD_CAM_EDM_DRO] CNCing a big surface grinder ?

> >Alternately, what's the feasibility of spending a few bucks on
> >electrical hydraulic valves? You'd still need some form of
> encoder for
> >positional feedback, but no need to tear into the treadmills.
> >
> >
> Ugh! A bad choice. Back in the relatively early days of CNC, many
> machines were made with hydraulic motors for brute force, and
> proportional servo valves as the amplifiers. This required a
> hydraulic
> pump running into a pressure relief valve, so that the system drew
> maximum electrical power all the time, and dissipated the heat from
> the fluid in big coolers. (Why they didn't use variable-displacement
> pumps, I don't know.) The noise, power consumption and maintenance
> headaches were huge, and as soon as power electronics got to the point
> that large electric motors could be controlled with electronic servo
> amps, all these machines were retrofitted or scrapped.

This was very useful information for me! I'm looking at buying an old VMC for retrofitting with EMC or other computerized control. The ting then would be to avoid the hydraulic ones. How do I know which ones are hydraulic???? It's not always that easy to know on many of the ones offered on ebay. But generally what type of controller it have is mentioned. I assume it is possible to find out what drive system is used by looking at the controller system?

I tried to find out by looking at Fanuc WebPages to se if they had any info on the different older systems. But the only thing I found there is info about all the fancy new ones. No info on older systems. Does anyone here have info about this???

At about when did they go from hydraulic to servomotors? And what year model would be about the oldest that you would recommend for this, I mean to avoid having to rebuild the whole machine completely at astronomical costs or years of work.

Anders