Ideas for automating hydraulic forming press

[kallileo]

There is a very old manually operating hydraulic forming press in our production. At the moment it's out of operation due to some issues with the hydraulic pump but are going to fix it and I have been tasked to install some kind of safety system.
We have already covered it completely from 3 sides and installed a sliding door on the front and next we will add some safety switches on it.
As far as I understand the automation system is basically are Y/D starter for the motor of the pump utilizing some extremely old Siemens relays that are still working but will be replaced anyway.
These are the requirements by our production manager.
At the moment the operator just presses the button to start the pump and monitors the analog pressure gauge on the pump.

I was thinking I could add some real value to the machine by installing a pressure sensor next to the analog gauge which will provide feedback of press force to a PLC+HMI system in order create recipes for various types of workpieces and have automatic operation and better repeatability.

Any other ideas that could be implemented on this type of machinery?
What about replacing the Y/D starter with a soft starter?

 

[GaryS]

I would have to consider if a PLC is the best choice have a look at Parker ACR 1000
they are probably the best for hydraulic systems
system using modulating hydraulic valves with real time both position and pressure feedback
those system can get to be very complex do your evaluation carefully
I think it would be an interesting project to work on
keep us posted on how you make out, maybe post some pictures for us

 

[kallileo]

There is no way to get budget for a hydraulic controller to be approved...

I'm not even sure that the simple PLC+HMI control will be aproved.

Sick has a some sensors specificaly desidn for hydraulic systems but I was thinking just about this force press sensor.

https://www.sick.com/ag/en/industri...l-presses/monitoring-of-press-force/c/p346560

It seems that both the down half of the press as well as the upper can move.
Normally the down half is moved using the hydraulic system and the upper side is stationary. But there is a geared motor that can move the upper side at as well probably just to increase the work volume. It's not connected at the moment but I will wire it into the control new panel.

I'm attaching some photos.

 

[Peter Nachtwey]

Presses should use a strain gage to measure force. Measuring the pressure on only one side of the piston leads to inconsistencies because there is pressure on the other side of the piston too. Then the net force should be calculated using
Net Force = Area A * Pressure A - Area B * Pressure B
However, even this calculation doesn't include force lost due to static friction.


This press must not be making valuable parts if the owner is not willing to invest much in it.

 

[kallileo]

Thank you Peter
Do you have any examples on how to use or install a strain gauge?

I see that the maximum medium temperature for some sensors is 80 C and for other is 120-130C. Could oil temperature in a hydraulic press be an issue and require high temp pressure sensor?

 

[thingstodo]

I would have to consider if a PLC is the best choice have a look at Parker ACR 1000
they are probably the best for hydraulic systems
system using modulating hydraulic valves with real time both position and pressure feedback
those system can get to be very complex do your evaluation carefully
I think it would be an interesting project to work on
keep us posted on how you make out, maybe post some pictures for us

The Parker forums state that the ACR 1000 is obsolete. Is there a successor?

I don't want to talk to a local Parker Salesman

 

[Peter Nachtwey]

Thank you Peter
Do you have any examples on how to use or install a strain gauge?

This is from our customers on our site.

https://forum.deltamotion.com/t/load-cells-and-signal-conditioners/109
My company makes hydraulic motion controllers


I am sure our motion controllers would be too expensive but a large percentage of hydraulic press manufacturers in the US and Canada use our controllers.

I see that the maximum medium temperature for some sensors is 80 C and for other is 120-130C. Could oil temperature in a hydraulic press be an issue and require high temp pressure sensor?

The oil shouldn't get that hot 55 degrees C and certainly no more than 60 degrees C. Otherwise the oil starts

I see that the maximum medium temperature for some sensors is 80 C and for other is 120-130C. Could oil temperature in a hydraulic press be an issue and require high temp pressure sensor?



https://www.mobilehydraulictips.com/how-hot-is-too-hot-for-hydraulic-oil/


Load cells are just metallic strips arranged electrically in a bride. They won't get damaged by the heat but they will change readings due to thermal expansion. It is the electronics or strain gage amplifier electronics that can't get too hot.



In the US and CA, Parker has a deal with Delta Computer Systems where their distributors can buy from Delta. Parker itself uses our controllers even thought they have their own that is made in the EU somewhere.

 

[GaryS]

Parker ACR 9000
http://www.parkermotion.com/products/Controllers__6934__30_32_80_567_29.html
I would look at that for your project
the price is in the same rang as a good PLC
I think you need to be careful with your budget when add up all the sensors, controllers and HMI your boss may not be supportive

 

[ndzied1]

Sick has a some sensors specificaly desidn for hydraulic systems but I was thinking just about this force press sensor.

https://www.sick.com/ag/en/industri...l-presses/monitoring-of-press-force/c/p346560

The sensor that you reference in your link is designed to be attached to an IO-Link Network. If you already had an IO-Link network on the machine or any sort of network that an IO-Link master could be connected to then this sensor could be a good choice.

Since you don't even have a PLC we know that you don't have any network right now. For a single sensor, adding a network doesn't make a lot of sense. Several vendors, probably including SICK make these sensors with an analog output which would be wired to an analog input on a PLC. Search ifm, Balluff, Rexroth, Hydac.

Another question is how is the pressure being controlled right now? You mention the operator watching the gage for the right pressure? Is he/she moving a knob on a relief valve to adjust pressure? If you want to do this automatically, then you need a electro-proportional valve. Or is it something like the press is slow enough and the part is squishy enough that the operator watches the gage as the part is compressed and the pressure increases? Then just switch a valve to open the press after the proper reading is reached?

I would not bother with a soft starter if you already have a Y/D starter. Soft starters have a limited number of starts per hour. Especially low cost ones can catch fire if you turn them on and off more often than specified in the manual (not allowing the internals parts to cool down). If you don't always use full speed on the press then a VFD could make sense for noise and energy savings. You still have to worry about starts per hour or get a version with a Safe Torque Off (STO) feature which I would recommend anyway. Then you can leave the mains power to the VFD on and stop the motor safely (so long as you follow the stop circuit in the manual of the VFD).

 

[kallileo]

Thank you all for the information.

@ndzied1
Yes, this sensor is too expensive.
I have found simpler and much cheaper versions without IO Link from Sick and Wika.

The press is very slow.
There is a metal lever on the pump unit which the operator pulls to move the press up and watches the pressure gage until the right pressure is reached, then he keeps the part at that pressure point for couple of seconds and then he pushes the lever back to move the press down. I guess valve switches to open and close. There is no proportional valve there.
The lever has 3 positions: middle=not moving, forward=move up and backward=move down.

Either way the hydraulic unit is going to be serviced so I will ask for the pressure sensors to be installed and also check the valve.

 

[lfe]

The press is very slow.

Large presses usually have two hydraulic circuits, one of low pressure and high flow to move the cylinder quickly and another of low flow and high pressure for the final thrust. This would increase production

 

[Peter Nachtwey]

Large presses usually have two hydraulic circuits, one of low pressure and high flow to move the cylinder quickly and another of low flow and high pressure for the final thrust. This would increase production

That thinking is kind of old school. Pressure does not form a piece, energy goes. While many presses simply using hydraulic pressure x area to form a part it is slow. A forming a part requires energy. Kinetic energy will do. Often the platen/slider is very heavy and a little speed will provide enough kinetic energy to form the part. The trick is to control the impact speed so it has just enough kinetic energy and maybe a little bit more. Impacting at too high a speed will cause pressure spikes and may not form the piece right or tear the metal. Impacting the work piece too slow will not provide enough energy and will require that the pressure build up enough to form the part. This wastes time.


I am often asked if the controller can use only on set of gains for all the different parts that the press makes. For the most part the answer is yes. What changes is the impact speed because different parts require different amounts of energy to form.


Now here is the trick. Presses heat up so the distance to the work piece will change so the ramps and impact speeds must be adaptable to compensate.


Also, adding some cushion makes controlling the force during impact possible. There is no way a valve can response fast enough to a pure metal on metal impact.

 

[lfe]

I have never seen a hydraulic press acting by impact ... If the author says that the press goes very slowly, it is even clearer that it does not act by impact.

I have seen many flywheel impact presses but nothing to do with hydraulics, maybe just to control the clutch.

 

[Peter Nachtwey]

I have never seen a hydraulic press acting by impact ...

If the press impacts with speed the kinetic energy will help or completely form the part. Mechanical presses work this way. They rely on a cushion to adjust the force.

If the author says that the press goes very slowly, it is even clearer that it does not act by impact.

The OPs press may be slow. I was pointing out that a press with high and low pressure pumps may not be fast either.
It was clear to me the OP didn't want to spend that kind of money or have the need for that time of speed or precision.

However, it is good to know what can be done.

I have seen many flywheel impact presses but nothing to do with hydraulics, maybe just to control the clutch.

This may be what you have seen. Often these presses have cushions that can be adjusted up and down and even start backing off just before impact to reduce the excess force and adjust for the temperature changes.


Many major press manufacturers use our hydraulic motion controllers for their press control. It has been a while since I have been to a metal forming show in the US but the last time I walk the show about 1/3 the press manufacturers use our controllers. Most of these were the high end press manufacturers. I have been to some of their plants and have help setup a few 20 years a go. No others do it and we still help out customers with press control.

 

[Highland Controls]

ACR9000 is probably overkill for this. Compax3 had a hydraulic control version.