There are 6 linear actuators in my system needs to move with each other at same speed.I need to divide 81 lit/min flow of a gear pump equally between these actuators.How can I divide this equally so that they have equal speed and they will be load-independent

quote:

Originally posted by John Milton:
There are 6 linear actuators in my system needs to move with each other at same speed.I need to divide 81 lit/min flow of a gear pump equally between these actuators.How can I divide this equally so that they have equal speed and they will be load-independent

More info will be needed to allow the denizens of this forum to give a definitive answer.

Are all actuators the same ..I assume that they are but you never know?
Is the positioning difference between the actuators critical?
What is the load difference between each actuator likely to be?
etc etc

OR ...Will a flow divider suit your purpose.
http://www.haldex.com/en-gb/Eu...%2Fflow_div_1205.pdf

Regards Woody

all the actuators are same and they need certain amount of flow to move simultaneously.positioning is critical as long as they must carry the load up without any collapse.The load difference exist in the system.
The already mentioned haldex flow divider can provide up to 4 output only

Commercial/Parker flow dividers get much bigger and can be multi-sectional. If high accuracy is required, look at motion controllers and temposonic cylinders.

http://www.unwinhydraulic.co.u.../_attachments/17.pdf

I have contacted Permco Gear Pump manufacturer (wwww.permco.com) they told me that 6 section flow divider is not stable as long as they must choose 05 and 07 gear width and this will lead to efficiency loss.They told me that i can use 3 section flow divider.Any idea how to divide the 3 outputs considering the fact that cylinders shall work load independent. can i use haldex flow divider http://www.haldex.com/en-gb/Eu...%2Fflow_div_1205.pdf to divide each section to 2 outputs?

You could use series or rephasing cylinders for this application depending on the force & stroke or travel required.

Synchronizing 6 hydraulic actuators is easy.

quote:

rephasing cylinders

The cylinders currently exist and we don't want to invest again on using rephasing cylinders.I would like to know if using a 3 output flowdivider with 3,two output flow divider works out or you can offer me another solution

You are looking for a quick and cheap solution, but what is the maximum error in positioning (among the cylinders) ?

I say this because, flow dividers are not very precise. 10% is very common, 5% the best. if you need less error, you need a different solution like using servo valves, position transducers, etc

Hydraulic Calculations, Pumps, Motors

kamil rhu has correctly pointed out that there is a difference between dividing flow and synchronizing axes. Synchronizing axes is easy dividing flows precisely is......impossible.

quote:

Originally posted by kamil rhu:
You are looking for a quick and cheap solution, but what is the maximum error in positioning (among the cylinders) ?

I say this because, flow dividers are not very precise. 10% is very common, 5% the best. if you need less error, you need a different solution like using servo valves, position transducers, etc

Hydraulic Calculations, Pumps, Motors

Can you guide me through using servo valves as a dividing means?

quote:

Originally posted by John Milton:
Can you guide me through using servo valves as a dividing means?

Yes, first you should know that this is done all the time. You need:
1. 6 servo valves or servo quality proportional valves. The quality,frequency response, of the valve depends on how dynamic you application is.
2. Each axis needs feed back. Usually a MDT rod is used. See
http://www.mtssensors.com/index.html
http://www.balluff.com/Balluff...ulse+Transducers.htm
3. A motion controller capable of coordinating 6 hydraulic actuator is required. Rockwell's Control Logix can do this with 3 1756-HYD02 or 3 1756-M02AS cards. The Delta Computer Systems RMC150 can do this too..
4. The supply pressure should be kept relatively constant. This means that the system should have an accumulator big enough so that the pressure doesn't drop more than 10%.

The motion controller uses the postion feed back from the MDT rods to correct for any differences in position.

This option will cost A LOT more than using flow dividers but it will also work when loads change and the systems wears and leaks. The motion controller always knows the the position of each actuator. The actuators can be stopped anywhere along the stroke, not just at the ends like flow dividers.

As per my knowledge it is better to use Pr. compensated flow control valve.

quote:

Originally posted by Sundar:
As per my knowledge it is better to use Pr. compensated flow control valve.

So how does a pressure compensate flow control valve synchronize actuators regardless of load?

What is the goal?
1. To divide flow?
2. To synchronize cylinders regardless of load.
If it is the latter position feedback is required.

Get serious guys. If you want to know why hydraulics is being left behind it is because now one want to move ahead with new technology.

Electric motor guys, you know the ones that you complain you are losing business too, would never use a motor with out position feedback when trying to synchronize actuators.

This message has been edited. Last edited by: Peter Nachtwey,

Agree Peter. Kind of like asking Burt Rutan to get into low Earth orbit and giving him an old Buick.

ISZ