Hydraulically Powered Machine Tool???

Grits · May 5, 2007

Has anyone every seen or heard of any machine tools being run with hydraulic motors. In my opinion, it would be a smooth, variable power source with plenty of torque. What am I missing?

Grits

Airborne · May 5, 2007

There's this "tricept" thingy that was introduced a few years ago. AFAIK, it was bloody expensive and bombed in sales.

Can't see how hydraulics on typical machines would be all that useful. Where's the cost savings?

wippin' boy · May 5, 2007

many high production machine tools use hydraulics
but they are moving towards independent servos these days

Tyrone Shoelaces · May 5, 2007

I worked on a " Marwin " HBM once that was totally hydraulically powered, even the spindle motor was hydraulic. It was very powerful for it's size but like most ( all ? ) hydraulic machines leaked like a sieve. I think Kearney and Trecker later bought Marwin out. Binns & Berry lathes had a hydraulic drive to the headstock gearbox, nicely variable but again had a habit of leaking like a sieve.
The hydraulic drive was almost impossible to get at so the leaks just got worse and worse, I had to top up the tank every week and throw chicken **** granules on the floor to mop up the leaks, the shop labourer later swept this up. A labourer saw me topping up one day and said " Why don't you just cut out the middle man and pour the oil straight onto the floor ? "

HelicalCut · May 5, 2007

Hydraulics, are a good power source but they are falling out of favour in machine tools for a few reasons I can think of: Expensive components, oil disposal and leaks, the controllers now are electric and it is relativly easy to control electric motive power with electric controls compared to hydraulic with electric, availability of high power density servomotors and compact low backlash high torque gearboxes. Hydraulics still excels at extremely high power density applications, applications which have to operate in wet conditions and applications which need large amounts of force.

Walt @ SGS Inc. · May 5, 2007

Anybody ever heard of a Hydrotel?
Anyone ever heard of a dither valve?
And they were smoth when moving.
They would not hold still when they
were not moving.
Seems like they were in a dither most
of the time.
Regards Walt...

Robert Campbell Jr. · May 5, 2007

Inefficiency.

Gear trains, belts and shafts with U joints all generate some heat but they pale by comparison to the waste heat produced by hydraulics doing the same work.

Because of this, motion by hydraulics can't compete cost wise with the more efficient mechanical motion transfer devices in most applications.

Bob

Mud · May 5, 2007

Visit an Amish machine shop or woodworking shop and you'll see lots of machines converted to hydraulic motors powered by a diesel powered pump. Noisy, messy, expensive, high maintenance.

surplusjohn · May 5, 2007

I have sold many machines to the Amish who then converted to hydraulic motors.

appliedproto · May 5, 2007

Mr. Campbell has it right, inefficiency. Electric motors and servomotors have to be an order of magnitude more efficient. A Mazak 12,000rpm spindle can get to top speed in under 2.5sec...with hydraulics I can only predict it would be a lot slower. Also it would be just be another heat source for thermal growth to the surrounding machine components.

John Michael · May 5, 2007

Earlier in NC some NC machine tools had hydraulic axis drives. I know of some cases where the early SCR drives were not big enough for a heavy axis and hydraulics were used. Some early Monarch NC flat bed lathes had Hydraulic drives. They were very strong and could break machine parts when out of control. I don't have first hand knowledge but it is my understanding that Monarch had an NC lathe with hyd. a cylinder to drive the X slide but had to change them out for ballscrews and hyd. motors because a hyd. cylinder full of oil has a mechanical resonance or natural frequency that resulted in chatter problems. Hydraulics were also used in early times to get more axis speed than the early servo motors could deliver. LeBlond had lathes with hyd. servos.
A big problem was keeping the oil clean enough not to jam the close tolerance servo valves.

Ries · May 5, 2007

Hydraulics are used in lots of tools- tools that need high torque, low speed motors.
They just arent very good for high speeds- certainly a lot of hassle, and expense, to get a hydraulic motor to run at 2000 or 3000 rpm. Much less 10,000 or 15,000.

But for things that move at fractional rpms up to maybe 20 rpm, there are tons of em- my shop is full of fab tools that are hydraulic, or would be if I could afford the more expensive models.

Hydraulic ironworkers are the bees knees.
Independent 3 roll angle rolls use 3 hydraulic motors- its widely acknowledged to be the best.
Shears and brakes are hydraulic.
All kinds of presses.

My buddy uses hydraulic motors on all the winches on his tender- he is in Alaska right now, buying herring from fishermen. In a nasty salt water environment, the hydraulic motors outlast and outwork electric, and don get short circuits, either.

So for low speed, high torque, high load applications, they are great. But not cost effective or efficient for high speed machining.

3t3d · May 5, 2007

Some of the very first disk drives, from the late 60's had hydraulic power to move the head into and out of the platters.
Granted, the disk platters were over three feet in diameter, and the the drives would fill up a small garage, and they did hold a few hundred kilobytes of data. They leaked like a sieve, and the hydraulic power unit was a seperate "tender" unit, near the drive, with the hoses going under the false floor.
They used a small dither valve to move the head arm assembly.

I also have (recently) seen a G&L mill with all hydraulics on the axis motion. It had about 12 feet of X axis motion, with a hydraulic motor, and a rack and pinion drive. The X axis feedback was a strip of Inductosyn rails, all mounted end to end.

Bill D · May 5, 2007

I saw a tablesaw run by a water turbine motor that turned a v belt to run the blade. I think it is Grass Valley California that had Pelton wheel (water turbine) direct driving a vee twin air compresssor for mining use. I thin kthis was made before electric motors existed. I belive it was 1500 -2000 HP.
BillD.

http://www.nevadacountyhistory.org/htmls/northstar.html

Forrest Addy · May 5, 2007

Hydraulics - even the best hydraulics - leak. If the don't at the moment, they will later. Hydraulics showed much promise in the early '50's (tracers and tracer attachments for example) but later technology has replaced them except for applications where very large controllable forces are required from compact simple equipment like presses, dump trucks, earth moving, etc.

[ 05-06-2007, 12:04 AM: Message edited by: Forrest Addy ]

Owen McGee · May 5, 2007

Hydraulics??? HeHeHe....anyone else remember the Moog Hydropoints????

OMcG

Engine Room Artificer · May 6, 2007

Good thing about hydraulics is that one pump can power many items and dependant on how the control valves are done the output is continuous ly variable and instantly reversable. Also you can get linear as well as rotary output from the same pump.

Grits · May 6, 2007

Thanks everyone for jumping into this topic and satisfying my curiosity.

I am a turf farmer. All of our harvesting, washing, laying, and everything else you can think of have hydraulic motors on them. Power not ever a problem but they do leak, lines break, and they will get hot and quit. On the flip side, we work in a very dirty environment and they do the job well. I live in Arkansas and everything is hot in the summer. We have added additional cooling to many of our machines.

I am trying to figure out how to rig up a heat exchanger to cool the hydraulic oil on a sod washer. The key will be to keep the hydraulic oil at its optimum operating temperature. The water source is 58F.

Thanks again for the good conversation.

Grits

GregSY · May 6, 2007

As other noted, Hydraulics are higher maintenance and much less efficient than an electric motor. the also offer a much less smooth power delivery than a motor.

appliedproto · May 6, 2007

I am trying to figure out how to rig up a heat exchanger to cool the hydraulic oil on a sod washer. The key will be to keep the hydraulic oil at its optimum operating temperature. The water source is 58F.

A good start is to talk to the manufacture on how many BTU's the system needs to shed, and what the current system is rated for. You'd be surprised how many manufacturers skimp on proper hydraulic cooling systems (especially on low production/specialty equipment). A laser thermometer is a great resource to determine which components are running hot and will fail prematurely. "Hydraulic Harmony" is something that is screwed up way too often with improperly sized motors, pumps, manifolds and hydraulic reservoirs.

Return temp of hydraulic oil should be ~130-140F. You don't want it under 120F or over 160F. Or, if you can't keep your hand on the return tank for more than 3 Mississippi...you probably got a problem.

Hydac make very nice compact heat exchanger units, with their rated BTU values. Even Northern Tool might have some very basic exchangers that might suite your application fine. Be advised though that with the additional plumbing and fittings the $$$ adds up quick! See if the rework would be reimbursed under warranty as well.

Hydraulically Powered Machine Tool???

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