Re: [CAD_CAM_EDM_DRO] replacing feed screw with a hydraulic cylinder

On Tue Nov 5 09:53:55 2002, Jon Elson, <elson@...> wrote:

>al5502 wrote:
>
>>Did somebody try to get rid of the feed screw all together
>>and replace it with a hydraulic cylinder?
>>At the first glance it may present several advantages:
>>no backlash, big force at low cost.
>>
>>
>We go through this every 6 months or so. It looks neat at first glance,
>and if you
>have lots of hydraulic gear around, might even be affordable.
> Proportional (Moog)
>valves are REALLY expensive, like $3000 and up! The hydraulic pumps are
>expensive,
>massively power-hungry, and LOUD! The hazards of a hydraulic leak at
>3000 PSI
>are very serious. You get oil injected under the skin, and it poisons
>you. A flexible
>line blowing off can also be dangerous. If there is any air in the
>system, it tends to
>go crazy with oscillation. The performance can be iffy, too, with
>jitter and stick-slip
>friction.
>
>I think if you add up all the parts costs, even surplus, you could go
>out and buy a complete
>ballscrew retrofit and servo drives new!
>
>Jon

All too true, but here's a question:

From the accuracy/resolution standpoint, what about slapping an encoder and
ballscrew/acme thread/timing chain onto a hydraulic motor, and as a way to
ditch some of the more complicated servo power supply/amplifier/control issues?
looks do-able, at least at first glance.

Bill

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