4 cylinder synchro short stroke 10-150mm 90 mins per stroke

[kebecano]

Hi all, I'd like your opinion on a certain system where 4 cylinders are to be synchrod within ± 0.5mm

Stroke is 10-150mm the stroke has a ±90 minute duration iow the 4 cylinders will have to extend lets say 150mm over the course of 90 minutes.

Initial design is to be closed loop with vickers kbf dg4v3 valves/amps

2 vickers pvm045 pc pumps, one accumulator, baluff rod sensors,

valves are supplied with pc stack valve flow controls

Trying to get the best possible results here..

I'm not sure this is the best way to proceed because of the very,very small flow required.

the 2 pumps are needed in order to provide high flow for fast stroking of cylinders once in a while over the full stroke.

Thanks for any suggestions,

p.s.

Peter N. : I suggested and RMC for control of the closed loop and due to our restrictive parameters but it was mentionned the system would be plc controlled.

KEbecano

 

[kebecano]

is this forum still active?

 

[hydromech]

Yes it is still active, although not as active one would like.

It seems that the system does not need to be dynamically responsive, so it would be possible to control the position of the cylinders relative to each other with simple positional feedback to the PLC. The PLC could then move or slow each cylinder to maintain the synchronisation.

How big is the acc...why have 2 pumps?

It would seem that the easiest way is to charge the acc, depending the volume and use the PLC to operate respective directional control valves to position the cylinders.

Other parameters need to be considered such as cylinder load etc.
Also the resolution of the Baluff sensors.

Hydromech

 

[PNachtwey]

The restrictive parameter was probably price but it is a trade off between price for the controller and ease of getting the system to go. It is probably worth while to roll your own if you are going to sell many but if not then development time is a killer as its costs can't be spread over many systems.

Fortunately you are moving extremely slowly so the project requirements should be easy to meet how ever you do it.

I would consider using one motor with an accumulator to supply the burst of speed. You haven't indicated what the bore is but the total volume of oil required to move quickly must not be much.

At 10mm/90 min the position will change by 1.8 by about microns every second. The position will appear to bump from one count to the next. If the feedback resolution is 1 micron then there will be many milliseconds between seeing the count change. Whether using a PLC or motion controller there will be many scans where the position doesn't appear to change.




Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

 

[kebecano]

Hydromech: Planned acc. vol is 1/4gal. There are 4 cyls, 6" bore 20" stroke.

Regular operation, rising for 10-150mm in 90mins

need for high speed stroking as well over the entire 20" in 16 secs. so about 36,72 gpm required during 16 seconds.

this is a one-off, retrofitting of an existing system.

Steel plant app. cont casting machine. 2 pumps required for backup purposes, and considering the fact that current planned acc. sizing is 1/4 gal right next to the valve and cylinders.

The distance between power unit and actuators is pretty long (hydraulic rigidity), therefore this is why I was thinking a larger acc maybe 2gals, which might help the system remain accurate and avoid hunting its position.

separate amp card or on board? I'm thinking onboard to reduce fiddling on valve setup etc...

Thank you both for your info, and please keep feeding me info on this.

This has to work right off the bat!

Thanks

Kevin