Hydraulic lathes?

Sometime recently I read about someone who acquired an older milling machine that had hydraulic feed on the table. I wondered about how
these tables might be controlled and if any lathes have been designed using hydraulics to move the carriage or crossfeed instead of lead or feedscrews. (After all, there are mechanical, hydraulic and pneumatic linear actuators.) I don't know if you could control hydraulics as precisely as feedscrews (with respect to headstock spindle rotation) for cutting threads, but you'd never have to worry about worn screws and metric/ inch conversions. I imagine that the big problem is in designing the feedback system and getting it to respond well. I've seen descriptions of hydraulic systems made by companies like Enerpac that control the balancing of bridge sections to keep them level while being positioned with cranes. I know that hydraulics can be controlled with electronics and proportional or servo valves. Probably it's difficult to beat mechanical feed and leadscrews because it's a simple and accurate system, but I was just curious.
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We have an older NC lathe, "Sheldon Tape Lathe" that uses Moog proportioning valves.
IIRC The valve needs a 0-20 mV signal to operate. Our resident electronical guru made us a pair of boards that turns +/-10V servo control signal into the signal that makes the Moog valve happy.
We retrofitted using a galil dmc740 motion controller.
This works great for really big iron.
Unless you NEED it, I'd try to avoid hydraulic servos.

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On Thu, 31 Jul 2008 12:56:31 -0700 (PDT), "Denis G."

Hydraulic duplicating (tracer) mills and lathes were once common. Last I knew a customer of mine was still using a tracer mill to duplicate molds for shoe counters for which there was no CAD data available. Google True-Trace or Mimik and you may find some info.
Sinker EDM rams were often servo-hydraulic, but, I think, not so much for coordinated motion as for smooth motion at very slow speeds
All the large planers I've seen were hydraulically driven, though that's more for brute force rather than controlled motion.
--
Ned Simmons

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wrote:

Small point, but the primary reason was that hydraulics could handle the quick reversals -- often several times per second -- involved in the EDM servo motion, and do it with relative simplicity. They just used a voltage-sensitive valve switch. DC servos didn't have enough "first-pulse" torque to do it until some advances came along in servo drive controllers. The first ballscrew-driven servomechanisms for EDMs that were successful used stepper motors.

Production milling at one time was mostly a pass-through operation, a lot like planers. Before CNC, production parts were, wherever possible, designed so that you didn't have to precisely control the start and stop positions of the axis traverse.
-- Ed Huntress
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On Thu, 31 Jul 2008 12:56:31 -0700 (PDT), "Denis G."

This is something we do all the time and is very common on spinning machines because of the high forces required.
We can hold tolerances as well as if not better than a leadscrew because of no mechanical influences.
http://s32.photobucket.com/albums/d1/debco99/?action=view&current=Spinvid.flv
Our website is www.debcomachinery.com.
If you need any further info let me know
Daveb
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On Thu, 31 Jul 2008 21:44:22 GMT, snipped-for-privacy@nt.org (DaveB) wrote:

Interesting industrial video, but wow!! the next pic is a keeper :-) Care to share the details??? ED

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wrote:

snicker......
Daveb
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On Thu, 31 Jul 2008 12:56:31 -0700 (PDT), "Denis G."

Over 30 years ago I ran Sheldon lathes that were hydraulicaly controlled. We could hold .0001" easily with these lathes. They were 15 inch swing machines, I think. They had an adjustment called "dither" which kept the valves always in motion. This was to avoid the problem with "stiction". I don't remember if it was the valves, the actuators, or both that needed the dithering. Interestingly, I have two older CNC lathes with Fanuc controls that also use dithering. The servos always move a little. The repair man had to adjust one of my lathes when the dithering was out of whack, it would lose precise position and the finish would suffer. He told me the dither was left over from hydraulic systems. My newer CNC controls no longer have a dither adjustment. ERS
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Hydraulic feed is an _old_old_ technology. Very inefficient also. Reliable control can also be a significant issue.
--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
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wrote:

We do it all the time with applications that make leadscrews impossible.
The last five machines we built have had zero follow-up calls.
This must be an area that you are unfamiliar with. Daveb
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snipped-for-privacy@nt.org (DaveB) wrote in

Dave, We used to have a floor full of hydraulic fed machines. They work, but can be troublesome. We still use hydraulics for one axis on one certain CNC machine type (It is a CNC axis - X axis specifically). Works great, adjustable in increments of 0.0002 microns _diameter_. Very stable. But....when it has issues...it has serious issues and downtime and tuning can be a lengthy and tedious process.
--
Anthony

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wrote:

I agree Anthony, no one is more surprised how well the machines we build run than me.
I went way out as far as warranty on this type machine ,not really knowing how reliable they would be both from the software as well as hardware aspect.
One advantage we have is we build it, so it makes it easier to troubleshoot and tune.
Having good heat exchanger and well filtered oil is one important issue.
Look forward to meeting you at ITMS.
Daveb
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snipped-for-privacy@nt.org (DaveB) wrote in

A mistake in my typing......... that should have been 0.0002 mm (not microns) (0.2 microns)
I'll be at IMTS Monday and Tuesday. We all need to designate a place and time to meet up.
--
Anthony

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wrote:

I noticed the typo....at first I thought WOW !
Daveb
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I seen a special on Pro Baseball bat manufacture. Each player provides his favorite blank. They are numbered and stored. A hydraulic tracer lathe turns the bats with the master in the tracer.
Karl
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Tracers are a bit different technology than servo control. We used two true-trace tracer units in production for years.
I have one available for sale, by the way.

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Denis G. wrote:

I don't think that a hydraulic system could retain anything approaching the rigidity that you get from lead screws, so I don't see it as being a good candidate. I think you'd get such a springy feed that you'd be constantly bouncing off of hard cuts, then digging in too far when the cuts got light.
Notice that the cited examples (the mentioned tracer machines, the film of the metal spinning, old old mill with hydraulic feed) were all things where some fixture provided the rigidity, or where the precision of the feed wasn't critical.
I'll believe it if I see it, and you can pay me my going rate to do a feasibility study if you want, but it's not something that I'd recommend off the cuff.
--

Tim Wescott
Wescott Design Services
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wrote:

We have built machines that free spin.......no tooling. This is how most cng cylinders are made to eliminate welding.
The last one we built was 75 hp (spindle) and we were forming .375 material cold.
example: http://www.leifeldspinning.com/necking_in_machines/necking_in_machines.htm
On our website the pnc 75 shown also has a turning holders as they do 2nd operation work.
There are plenty of turret type machines that do both turning and spinning.
www.debcomachinery.com Daveb
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On Fri, 01 Aug 2008 02:05:02 GMT, snipped-for-privacy@nt.org (DaveB) wrote:

BTW Tim, if you can afford my rates I may show you how its done. If your at ITMS would like to show you what we have (for free) Daveb
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