Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Gregg Eshelman]

On 11/9/2015 1:26 PM, Roland Jollivet wrote:
> I don't see why it has be this way. Running a pump at full power past a
> valve sounds daft. That's why the new pressbrakes, presses and injection
> moulding machines use servo hydraulics.
>
> Simply put, you have a gear pump, and both ends go to a cylinder. Turn one
> way, rod extends. Turn other way, rod retracts. Of course it's more complex
> than that, but the idea is that if there's no work to be done, the motor
> isn't turning.

If you could build a constant volume/displacement hydraulic system, with 
no accumulator or other buffer that takes fluid out of the main circuit, 
you could have a linear relationship between whatever moves the oil and 
the cylinder that gets moved.

If you had a cylinder with the same volume and stroke, and same rod 
diameter, it should be possible to connect the end with the rod of each 
cylinder to the other end, without the rod to keep the two volumes the 
same. Push or pull on the external cylinder and the one on the machine 
should move the same amount.

Connecting rod end to rod end and the rodless ends together wouldn't 
work due to volume changes. The cylinder pair would be locked up.

How to drive it? Mount screws parallel to the driving cylinders and 
arrange them all vertically on a frame.

One use for such a setup would be retrofitting old hydraulic CNC and 
tracer mills to modern CNC systems for faster speed. Those old 
Bridgeport hydraulic tracers could rip along at up to 13" a minute. Wheee.

Looks like they would be a nightmare to keep running with all the valves 
and switches and pipes and hoses going to and from the tracer, the 
cylinders and the pump and reservoir.

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Andrew]

2015-11-09 20:16 GMT+02:00 Jon Elson :

> On 11/09/2015 02:34 AM, Andrew wrote:
> >> there were hydraulic milling machines sold based on Moog hydraulics
> >> and Bridgeport iron.  I assume those two companies could screw things
> >> up, but the world has moved on.  To move a long distance takes a lot
> >> of power.  Small movements with a lot of force behind them are really
> >> easy, that's why you see fatigue machines and other shorter stroke
> >> machines with hydraulic servo.
> >>
> >> AFAIK the problem of hydraulic actuators is low efficiency. There should
> > be a high pressure high rate pump to provide high velocity and force. But
> > when the actuator doesn't move it all goes via baypass just heating the
> > fluid. Probably adjustable pump could help but it gets more complicated
> > (just a guess).
> >
> Yes, some systems had fixed displacement pumps and
> regulating valves, others had variable-displacement pumps.
> Then, you have to provide cooling for the variable
> displacement pumps so it doesn't overheat when the machine
> is idling.  In either case, the drive motor has to be quite
> huge, so there is plenty of energy wasted, and they make a
> HUGE amount of noise.  So much that sound barriers have to
> be placed around the hydraulic power pack.
>
> Talking about hydraulics and CNC...
There's an old (~40 years) CNC lathe in our lab
https://www.dropbox.com/s/9cxnv0luduo11uf/SAM_2154.JPG?dl=0
It has hydraulic boosters (amplifying valves) for the ballscrews
https://www.dropbox.com/s/nnkle9elu8lh90p/SAM_2157.JPG?dl=0
A low-torque stepper motor rotates the valve, then the hydraulics rotates
the ballscrew.
There's a pretty large hydraulic power unit behind
https://www.dropbox.com/s/bqajpxwd8xs4dd7/SAM_2219.JPG?dl=0
It has 7.5KW motor
https://www.dropbox.com/s/8ypf3d3yryb3dcq/SAM_2151.JPG?dl=0
We turned the lathe on some time ago, the noise was very bad.
Its spindle gearbox with electromagnetic couplings also makes a lot of
noise at high speed.
The whole CNC with hydraulics was very unreliable, so these lathes had not
worked for a long time back then.

Andrew
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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Dave Cole]

Yes, I would be surprised of those cylinders were not special.

I remember seeing those machines at GM when I used to work there years ago.

They could really beat a car's suspension up and they would run them for 
days and days to see if stuff would break, tear out, wear out,  etc.

They were really quite violent.I bet that hydraulic power system has 
a bunch of accumulators for super fast flow response.

Another one:
https://www.youtube.com/watch?v=paT-JNWWV-w
Looks like they have the servo valves mounted right on the cylinders for 
minimum response time..

Dave


On 11/9/2015 11:00 AM, andy pugh wrote:
> On 9 November 2015 at 15:32, Dave Cole  wrote:
>> I've done quite a bit of hydraulic servo work for custom machines.
>> You can use regular industrial cylinders for positioning.
> I imagine that the reason that fatigue testing machines use
> hydrostatic cylinders is that they want to be fatigue testing
> machines, not hydraulic cylinder seal testing machines.
>

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

On 9 November 2015 at 17:37, Dave Cole  wrote:
> They were really quite violent.I bet that hydraulic power system has
> a bunch of accumulators for super fast flow response.

That and (in our case) 2000hp of electric motors driving 20 pumps.

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Jon Elson]

On 11/09/2015 02:34 AM, Andrew wrote:
> 2015-11-09 8:49 GMT+02:00 Eric Keller :
>
>> there were hydraulic milling machines sold based on Moog hydraulics
>> and Bridgeport iron.  I assume those two companies could screw things
>> up, but the world has moved on.  To move a long distance takes a lot
>> of power.  Small movements with a lot of force behind them are really
>> easy, that's why you see fatigue machines and other shorter stroke
>> machines with hydraulic servo.
>>
>> AFAIK the problem of hydraulic actuators is low efficiency. There should
> be a high pressure high rate pump to provide high velocity and force. But
> when the actuator doesn't move it all goes via baypass just heating the
> fluid. Probably adjustable pump could help but it gets more complicated
> (just a guess).
>
Yes, some systems had fixed displacement pumps and 
regulating valves, others had variable-displacement pumps.  
Then, you have to provide cooling for the variable 
displacement pumps so it doesn't overheat when the machine 
is idling.  In either case, the drive motor has to be quite 
huge, so there is plenty of energy wasted, and they make a 
HUGE amount of noise.  So much that sound barriers have to 
be placed around the hydraulic power pack.

Jon

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Jon Elson]

On 11/08/2015 09:54 PM, TJoseph Powderly wrote:
> moog or pegasus. brands, those are the big names.
> they were used to move really heavy cast iron slides, often dovetail.
>
> messy ( plan on leaks and kitty litter )
> the hydraulic supply tops up the volume from a reservoir that you keep full
> these are really really beefy systems.
>
> the internal of the valve ( generic name spool valve) is like a voice coil,
> i doubt you can move the mass as fast as you can shake that spool.
>
> think linear scales to track the slides not the piston.
>
>
In fact, they typically add a dither to the servo command to 
the valve to keep the spool floating.  otherwise, there can 
be a bit of a jerk when it first starts to move.  
Allen-Bradley's hydraulic output module adds a 400 Hz 
triangle wave to the DAC output for this purpose.

Jon

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

On 9 November 2015 at 15:32, Dave Cole  wrote:
> I've done quite a bit of hydraulic servo work for custom machines.
> You can use regular industrial cylinders for positioning.

I imagine that the reason that fatigue testing machines use
hydrostatic cylinders is that they want to be fatigue testing
machines, not hydraulic cylinder seal testing machines.

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

Just for interest's sake, here is a 6DOF vehicle simulator in action.
It might recalibrate your ideas of how fast hydraulics can move:
https://www.youtube.com/watch?v=83PsmzwkVSs

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Dave Cole]

On 11/9/2015 5:37 AM, andy pugh wrote:
> On 9 November 2015 at 03:54, TJoseph Powderly  wrote:
>> messy ( plan on leaks and kitty litter )
>> the hydraulic supply tops up the volume from a reservoir that you keep full
>> these are really really beefy systems.
> Indeed, the power pack for my testing machine was contained in a
> soundproof wooden box about the same size as a car.
> At work there is a bank of 20 x 75kw (100hp) motors servicing a
> hydraulic ring-main for about 6 multi-axis shaker rigs.
> (But the rigs can play-back suspension /braking / acceleration forces
> and displacements on 4 wheels of a vehicle in real-time 25 hours a
> day)

I've done quite a bit of hydraulic servo work for custom machines.
You can use regular industrial cylinders for positioning.
For precise positioning and fast response you need to use a lot of steel 
lines.   Rubber hoses act like springs as they bulge and contract.
Servo valves are expensive.  $1000 is not a lot for a servo grade 
proportional valve.   There are cheap proportional valves but they are 
not made for precise positioning.   Some are just used for pressure 
control and are very slow to respond.   A swash plate piston pump can 
eliminate a lot of oil heating problems and energy waste.But swash 
plate piston pumps are much more expensive than gear pumps 3-4K for a 20 
hp pump is pretty cheap.
You can get by with a smaller pump by using an accumulator but those are 
thousands of dollars each also.

These are all reasons why people have migrated to electric servos and 
away from hydraulics.

Dave

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[Emc-users] could Linux cnc control of unconventional ... hydraulic

[Roland Jollivet]

I don't see why it has be this way. Running a pump at full power past a
valve sounds daft. That's why the new pressbrakes, presses and injection
moulding machines use servo hydraulics.

Simply put, you have a gear pump, and both ends go to a cylinder. Turn one
way, rod extends. Turn other way, rod retracts. Of course it's more complex
than that, but the idea is that if there's no work to be done, the motor
isn't turning.

I think the idea is great in that you can have a monster motor on the
floor, and small cylinders inside a machine. But I think movements in the
10's of Hz would cause too much oil heating, so better to just put a
ballscrew on the motor for a CNC machine.

Regards
Roland



On 9 November 2015 at 20:16, Jon Elson  wrote:

> On 11/09/2015 02:34 AM, Andrew wrote:
> > 2015-11-09 8:49 GMT+02:00 Eric Keller :
> >
> >> there were hydraulic milling machines sold based on Moog hydraulics
> >> and Bridgeport iron.  I assume those two companies could screw things
> >> up, but the world has moved on.  To move a long distance takes a lot
> >> of power.  Small movements with a lot of force behind them are really
> >> easy, that's why you see fatigue machines and other shorter stroke
> >> machines with hydraulic servo.
> >>
> >> AFAIK the problem of hydraulic actuators is low efficiency. There should
> > be a high pressure high rate pump to provide high velocity and force. But
> > when the actuator doesn't move it all goes via baypass just heating the
> > fluid. Probably adjustable pump could help but it gets more complicated
> > (just a guess).
> >
> Yes, some systems had fixed displacement pumps and
> regulating valves, others had variable-displacement pumps.
> Then, you have to provide cooling for the variable
> displacement pumps so it doesn't overheat when the machine
> is idling.  In either case, the drive motor has to be quite
> huge, so there is plenty of energy wasted, and they make a
> HUGE amount of noise.  So much that sound barriers have to
> be placed around the hydraulic power pack.
>
> Jon
>
>
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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Andrew]

2015-11-09 8:49 GMT+02:00 Eric Keller :

> there were hydraulic milling machines sold based on Moog hydraulics
> and Bridgeport iron.  I assume those two companies could screw things
> up, but the world has moved on.  To move a long distance takes a lot
> of power.  Small movements with a lot of force behind them are really
> easy, that's why you see fatigue machines and other shorter stroke
> machines with hydraulic servo.
>
> AFAIK the problem of hydraulic actuators is low efficiency. There should
be a high pressure high rate pump to provide high velocity and force. But
when the actuator doesn't move it all goes via baypass just heating the
fluid. Probably adjustable pump could help but it gets more complicated
(just a guess).

--
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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Karlsson & Wang]

> 2015-11-09 8:49 GMT+02:00 Eric Keller :
> 
> > there were hydraulic milling machines sold based on Moog hydraulics
> > and Bridgeport iron.  I assume those two companies could screw things
> > up, but the world has moved on.  To move a long distance takes a lot
> > of power.  Small movements with a lot of force behind them are really
> > easy, that's why you see fatigue machines and other shorter stroke
> > machines with hydraulic servo.
> >
> > AFAIK the problem of hydraulic actuators is low efficiency. There should
> be a high pressure high rate pump to provide high velocity and force. But
> when the actuator doesn't move it all goes via baypass just heating the
> fluid. Probably adjustable pump could help but it gets more complicated
> (just a guess).
> 
> --
> Andrew

Low efficiency is certainly a broblem so unless there is other advantages it is 
never a point to use hydraulics for this purpose.


Nicklas Karlsson

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

On 9 November 2015 at 03:54, TJoseph Powderly  wrote:
> messy ( plan on leaks and kitty litter )
> the hydraulic supply tops up the volume from a reservoir that you keep full
> these are really really beefy systems.

Indeed, the power pack for my testing machine was contained in a
soundproof wooden box about the same size as a car.
At work there is a bank of 20 x 75kw (100hp) motors servicing a
hydraulic ring-main for about 6 multi-axis shaker rigs.
(But the rigs can play-back suspension /braking / acceleration forces
and displacements on 4 wheels of a vehicle in real-time 25 hours a
day)

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Dave Cole]

On 11/9/2015 4:55 PM, Andrew wrote:
> 2015-11-09 20:16 GMT+02:00 Jon Elson :
>
>> On 11/09/2015 02:34 AM, Andrew wrote:
 there were hydraulic milling machines sold based on Moog hydraulics
 and Bridgeport iron.  I assume those two companies could screw things
 up, but the world has moved on.  To move a long distance takes a lot
 of power.  Small movements with a lot of force behind them are really
 easy, that's why you see fatigue machines and other shorter stroke
 machines with hydraulic servo.

 AFAIK the problem of hydraulic actuators is low efficiency. There should
>>> be a high pressure high rate pump to provide high velocity and force. But
>>> when the actuator doesn't move it all goes via baypass just heating the
>>> fluid. Probably adjustable pump could help but it gets more complicated
>>> (just a guess).
>>>
>> Yes, some systems had fixed displacement pumps and
>> regulating valves, others had variable-displacement pumps.
>> Then, you have to provide cooling for the variable
>> displacement pumps so it doesn't overheat when the machine
>> is idling.  In either case, the drive motor has to be quite
>> huge, so there is plenty of energy wasted, and they make a
>> HUGE amount of noise.  So much that sound barriers have to
>> be placed around the hydraulic power pack.
>>
>> Talking about hydraulics and CNC...
> There's an old (~40 years) CNC lathe in our lab
> https://www.dropbox.com/s/9cxnv0luduo11uf/SAM_2154.JPG?dl=0
> It has hydraulic boosters (amplifying valves) for the ballscrews
> https://www.dropbox.com/s/nnkle9elu8lh90p/SAM_2157.JPG?dl=0
> A low-torque stepper motor rotates the valve, then the hydraulics rotates
> the ballscrew.
> There's a pretty large hydraulic power unit behind
> https://www.dropbox.com/s/bqajpxwd8xs4dd7/SAM_2219.JPG?dl=0
> It has 7.5KW motor
> https://www.dropbox.com/s/8ypf3d3yryb3dcq/SAM_2151.JPG?dl=0
> We turned the lathe on some time ago, the noise was very bad.
> Its spindle gearbox with electromagnetic couplings also makes a lot of
> noise at high speed.
> The whole CNC with hydraulics was very unreliable, so these lathes had not
> worked for a long time back then.
>
> Andrew
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The pump might have lost its prime.   When they do they are very noisy.
Swash plate pumps can be quiet compared to gear pumps.Once they 
build pressure and there is very little flow the noise is not bad at 
all.Heating is not bad at all.
The old true servo valves were notorious for getting jammed up.   If the 
oil is dirty they stick.

Dave


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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Karlsson & Wang]

On Sun, 8 Nov 2015 15:47:37 + (UTC)
richsh...@comcast.net wrote:

> I suggest looking at a hydraulic approach. It eliminates all of the drive 
> lash problems with the rigidity problems that follow. Ingersoll Rand built a 
> prototype mill similiar to what you are describing, you may find getting in 
> touch with them to be useful. However it goes, I see this adventure of yours 
> to be an important step in pushing the technology window. Have at it. 

Hydraulic, that seems interesting how does hydraulic compare to a ball screw 
then it come to back slash and accuracy?

Nicklas Karlsson

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

On 8 November 2015 at 21:12, andy pugh  wrote:

>> I suspect if a valve is used an motor running dynamic response could be 
>> good, do you know if it had good dynamic performance.
>
> Yes, it was running closed-loop (on force) fatigue tests at 20Hz.

An example: https://www.youtube.com/watch?v=6Dms5MSO800

(The not-connected struts do the same thing to apply braking and
steering torques)

We have some at work, it's hard to walk past without watching.

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

On 8 November 2015 at 17:10, Karlsson & Wang
 wrote:

> Hydraulic, that seems interesting how does hydraulic compare to a ball screw 
> then it come to back slash and accuracy?

Accuracy is limited by the feedback device, I think.

Servohydraulic cylinders are a bit different to normal ones. They
generally don't seal the piston particularly, but a Moog-valve
controls the differential pressure across the piston and the servo
action compensates for any leakage.

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

On 8 November 2015 at 21:07, Karlsson & Wang
 wrote:

> I suspect if a valve is used an motor running dynamic response could be good, 
> do you know if it had good dynamic performance.

Yes, it was running closed-loop (on force) fatigue tests at 20Hz.

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Karlsson & Wang]

> On 8 November 2015 at 17:10, Karlsson & Wang
>  wrote:
> 
> > Hydraulic, that seems interesting how does hydraulic compare to a ball 
> > screw then it come to back slash and accuracy?
> 
> Accuracy is limited by the feedback device, I think.
> 
> Servohydraulic cylinders are a bit different to normal ones. They
> generally don't seal the piston particularly, but a Moog-valve
> controls the differential pressure across the piston and the servo
> action compensates for any leakage.

Servohydraulic cylinders have low friction instead of perfect sealing?

Nicklas Karlsson

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

On 8 November 2015 at 18:26, Karlsson & Wang
 wrote:

> Servohydraulic cylinders have low friction instead of perfect sealing?

The ones I have worked with, yes.

I was at the high-force high-accuracy end, though. 250kN 100mm stroke,
0.001mm resolution. (Schenck tensile tester)

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Karlsson & Wang]

> On 8 November 2015 at 18:26, Karlsson & Wang
>  wrote:
> 
> > Servohydraulic cylinders have low friction instead of perfect sealing?
> 
> The ones I have worked with, yes.
> 
> I was at the high-force high-accuracy end, though. 250kN 100mm stroke,
> 0.001mm resolution. (Schenck tensile tester)

I suspect if a valve is used an motor running dynamic response could be good, 
do you know if it had good dynamic performance.

Nicklas Karlsson

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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[ger Ger]

Any know if this Bodine motor would be suitable for a milling head ?

Bodine 42A5BEPM-E2
thank you,
other rick

On Sun, Nov 8, 2015 at 4:16 PM, andy pugh  wrote:

> On 8 November 2015 at 21:12, andy pugh  wrote:
>
> >> I suspect if a valve is used an motor running dynamic response could be
> good, do you know if it had good dynamic performance.
> >
> > Yes, it was running closed-loop (on force) fatigue tests at 20Hz.
>
> An example: https://www.youtube.com/watch?v=6Dms5MSO800
>
> (The not-connected struts do the same thing to apply braking and
> steering torques)
>
> We have some at work, it's hard to walk past without watching.
>
> --
> atp
> If you can't fix it, you don't own it.
> http://www.ifixit.com/Manifesto
>
>
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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[andy pugh]

On 9 November 2015 at 01:38, linden  wrote:
> Not sure how well the 24volt 5 way
> valves i have will put up with constant motion and at what speed.

You need proportional valves ("Moog Valves")

A hydraulic system could be excellent, but I see no way at all to do
it cheaply.


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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[linden]

I have some hydraulic bits and pieces laying around that may be usable 
for this. Just need to find some rams and or rig up some kind of 
position sensing system as the rams i have found with integrated 
position sensor are pretty spendy.  Not sure how well the 24volt 5 way 
valves i have will put up with constant motion and at what speed. I am 
sure I would reach the speed or duty cycle  limit of the valve long 
before ran out of speed on the solid state relays or the pid loop 
driving it.

more home work needed at this point.

thanks linden

On 15-11-09 08:24 AM, ger Ger wrote:
> Any know if this Bodine motor would be suitable for a milling head ?
>
> Bodine 42A5BEPM-E2
> thank you,
> other rick
>
> On Sun, Nov 8, 2015 at 4:16 PM, andy pugh  wrote:
>
>> On 8 November 2015 at 21:12, andy pugh  wrote:
>>
 I suspect if a valve is used an motor running dynamic response could be
>> good, do you know if it had good dynamic performance.
>>> Yes, it was running closed-loop (on force) fatigue tests at 20Hz.
>> An example: https://www.youtube.com/watch?v=6Dms5MSO800
>>
>> (The not-connected struts do the same thing to apply braking and
>> steering torques)
>>
>> We have some at work, it's hard to walk past without watching.
>>
>> --
>> atp
>> If you can't fix it, you don't own it.
>> http://www.ifixit.com/Manifesto
>>
>>
>> --
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> developed by Facebook, enables you to easily query your data on Hadoop in a
> more interactive manner. Teradata is also now providing full enterprise
> support for Presto. Download a free open source copy now.
> http://pubads.g.doubleclick.net/gampad/clk?id=250295911=/4140
> ___
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> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users


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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[TJoseph Powderly]

moog or pegasus. brands, those are the big names.
they were used to move really heavy cast iron slides, often dovetail.

messy ( plan on leaks and kitty litter )
the hydraulic supply tops up the volume from a reservoir that you keep full
these are really really beefy systems.

the internal of the valve ( generic name spool valve) is like a voice coil,
i doubt you can move the mass as fast as you can shake that spool.

think linear scales to track the slides not the piston.

tomp tjtr33


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Re: [Emc-users] could Linux cnc control of unconventional ... hydraulic

[Eric Keller]

there were hydraulic milling machines sold based on Moog hydraulics
and Bridgeport iron.  I assume those two companies could screw things
up, but the world has moved on.  To move a long distance takes a lot
of power.  Small movements with a lot of force behind them are really
easy, that's why you see fatigue machines and other shorter stroke
machines with hydraulic servo.

On Sun, Nov 8, 2015 at 9:16 PM, andy pugh  wrote:
> On 9 November 2015 at 01:38, linden  wrote:
>> Not sure how well the 24volt 5 way
>> valves i have will put up with constant motion and at what speed.
>
> You need proportional valves ("Moog Valves")
>
> A hydraulic system could be excellent, but I see no way at all to do
> it cheaply.
>
>
> --
> atp
> If you can't fix it, you don't own it.
> http://www.ifixit.com/Manifesto
>
> --
> Presto, an open source distributed SQL query engine for big data, initially
> developed by Facebook, enables you to easily query your data on Hadoop in a
> more interactive manner. Teradata is also now providing full enterprise
> support for Presto. Download a free open source copy now.
> http://pubads.g.doubleclick.net/gampad/clk?id=250295911=/4140
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