[SPEEDRE]

While dreaming the other day, I dreamed a machine that ran on hydraulics. No electric motors except the spindle. I don't know enough about hydraulics but could one work? I've seen cylinders that move real slow with plenty of forward motion, then ramp up to a faster forward motion. As I write I'm thinking what would tell the cylinders how fast to move and in what direction?. X and Y wouldn't be an issue it's Z that seems to pose an issue. What do you guys think, is it doable realistically or just a pipe dream?. Sure would be quiet, ya think?.

[CNC Lurker]

Another question would be is it cost effective or beneficial compared to other tried-and-true methods that has worked for countless others already (such as ACME threaded rods or ball screws).

[diyengineer]

While dreaming the other day, I dreamed a machine that ran on hydraulics. No electric motors except the spindle. I don't know enough about hydraulics but could one work? I've seen cylinders that move real slow with plenty of forward motion, then ramp up to a faster forward motion. As I write I'm thinking what would tell the cylinders how fast to move and in what direction?. X and Y wouldn't be an issue it's Z that seems to pose an issue. What do you guys think, is it doable realistically or just a pipe dream?. Sure would be quiet, ya think?.

That is a different idea for sure. Hydraulic cylinders are expensive as hell. especially long ones. Might have to make your own low cost ones, since it wouldn't see much force, compared to say a cylinder on a bobcat, or other heavy piece of machinery. Would be a pretty cool concept indeed. Making a cylinder controlled by mach would probably be your first step.

[thebodger@roger]

We had early generation NC machines the used servo valves and rotary hydraulic actuators ( motors) for positioning. They still had to have ballscrews to move the axis. The machines were made by Giddings and Lewis U.S.A, and Marvin of England. The reason they used hydraulics, was because the power electronics needed for electric servo motors, was not yet developed. The servo valve controllers ( amplifiers) were only needed to supply low voltage and current to the servo valve, so it was do-able with what was at hand at the time. I remember that the surface finish on the machined parts was not very good. The hydraulic motors were hard to control at low cutting speeds, and at stand still. These systems were quickly abandoned, once high power transistors came of age. Everything switched over to electric drives, the benefits were obvious.

[robe_uk]

Well I don't think its going to be any quieter than a 'normal' machine, the noise of the spindle cutting is the loudest sound and normally would drown out that of servos/steppers, also you will need a pumping system for the hydraulics and maybe a vacuum for dust control.

How would you get positional feedback for any controller to know how much to move any rams. Is there even controllers for the level of precision you would want from a cnc machine?

While I love to see new ideas i feel i would have to agree with CNC Lurker.

But anything is possible with enough smarts and cash

[Andre' B]

We had early generation NC machines the used servo valves and rotary hydraulic actuators ( motors) for positioning. They still had to have ballscrews to move the axis. The machines were made by Giddings and Lewis U.S.A, and Marvin of England. The reason they used hydraulics, was because the power electronics needed for electric servo motors, was not yet developed. The servo valve controllers ( amplifiers) were only needed to supply low voltage and current to the servo valve, so it was do-able with what was at hand at the time. I remember that the surface finish on the machined parts was not very good. The hydraulic motors were hard to control at low cutting speeds, and at stand still. These systems were quickly abandoned, once high power transistors came of age. Everything switched over to electric drives, the benefits were obvious.

I remember seeing one lathe advertised that used cylinders alone for motion. It was faster then ball screw and servo motors of the time but it had some moton control/rigity issues. Not sure what they teach nowdays but they used tell students that oil and water were not compresable like air, they were wrong.

And like you say now days modern electronics, motors, and screws wipe out any advantage the hydraulic systems may have once had.

[RICHARD ZASTROW]

Back in the ol' days (1960's) we had hydraulic servos on our Cintamatic NC's. Hydraulic pumps and motors were noisy and got hot. When they got hot, they got erratic. Lotsa' problems.

The old Hughes HMC's were twin tool turret hydraulic machines (leaked all over). I believe they were rebadged Burkhardt & Weber machines.

The G&L machines were pretty good, used Farrand Inductosyn linear scales for feedback rather than rotary resolvers or encoders.

More trivia than you really wanted, I suspect.

Dick Z

[SPEEDRE]

Not sure what feedback is, don't laugh. But as I said a hair brained dream to be sure.

[louieatienza]

Hexk, they have pneumatic actuators, you can drive everything with air, though that's got to be expensive!

[BanduraMaker]

What problem are you trying to solve with this idea?

[mlabruyere]

"quiet"....ever been near a hydraulic pump under demand?

My machine is very quiet running 600+ IN/OZ steppers on 1/2-10 5 start lead screws so long as the spindle isn't running.

If you are going to make a CNC wood splitter or other work that requires only gross movements with huge power then maybe this would be good...but you aren't going to get cuts within a hundredth or probably even a tenth of an inch with this.

[rockcliff]

The use of hydraulic cylinder positioning for use in cutting machines is not a new innovation, about 60 + years ago Bridgeport made a hydraulic positioned milling machine, called a (Bridgeport True Trace )

I actually owned one way back, ours was a dual head model, ( 2 full size Bridgeport J heads) and a 10HP hydraulic pump, truly an old school solid cast iron monster !!! we converted it to CNC by simply attaching an x-y-z positioner to the Hydraulic Servo control Valve, it ran off an early version of software called Master5 which we all know today as Mach3,

The cuts were ultra smooth, extremely precise, highly repeatable, and the slides had major power! it went on to cut thousands of pounds of steel for us for many years, before we retired it.