RE: [CAD_CAM_EDM_DRO] Re: replacing feed screw with a hydraulic c ylinder

What if you had one big pump to keep up the pressure and some kind of a
rotary valve on each axis that just lets a metered amount of fluid through
every time its activated.

Alternatively you could have a pump on every axis and calculate the pump
speed so that every axis reaches its goal at the same time.

If no-one dares to think differently then a possible 'better' solution might
never be discovered...

Cheers
Coert

-----Original Message-----
From: Jon Elson [mailto:elson@...]


b564htf wrote:

>I've thought about hydraulic drive CNC for years. This may have
>already been discussed but my idea is to use a closed system with
>single shot pistons powered by solenoids or a motor driven cam. Each
>stroke of the piston would pump a metered amount of fluid from one
>side of the cylinder to the other kind of like a hydraulic jack. One
>stroke of the piston would equal a fixed amount cylinder travel. A bi-
>directional piston with check valves could be used to change the
>direction. Example: 1000 piston strokes could equal 1" of
>travel, kind of like a linear stepping motor. A stroke counter
>could keep track of the position. This system should work with
>stepper motor software. Some obvious negatives I can think of: Slow
>speed (?), piston seal leakage, temperature may change volume of
>fluid (?).
>

Oh, this is GREAT! So, to move at 60 IPM (one inch/second) you need the
pump to pound out
1000 strokes/second! How long is that pump going to last at that rate?
What sort of device
is going to be able to drive the cylinder at such a rate? What would be
the efficiency of a
fluid pump moving so fast?

Actually, it is totally impractical to try to make a liquid pump run at
such a rate, cavitation
will cause it to be pumping vacuum, not oil. So, it won't be linear,
ie. fast strokes will pump
less oil than slow ones.

Jon


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