Single acting cylinder counter balance

[DaveGEA]

Hello all Dave from NC here I am new to this forum,

I could use some advise on a solution for a problem I have with a machine. background... I have a die press machine that utilizes an electric motor and worm drive gear box that raises and lowers a die vertically, attached between the load and the motor mount is a single acting hydraulic cylinder that is designed to remove any backlash in the gearing drive train.

An operator switches the hydraulic valve off relieving the line pressure then positions the load via the electric motor, the operator then switches on the hydraulic valve and applies pressure to the hydraulic cylinder thus further lifting the load removing any backlash. This operation works, well almost.

The problem I have is at the point when the hydraulic pressure is removed the load drops slightly releasing the backlash. I need to be able to keep the back lash under control. My thought is to use the motor to drive the load down against some of the hydraulic pressure as opposed to just releasing all of the pressure in the cylinder.

I thought about a counter balance valve but since there is only one oil line to the cylinder there is no pilot pressure available. Then I thought about installing an adjustable regulator on the Tank port of the valve but I think this would create a very erratic movement.

So I am really not sure what the best solution would be in this situation. Any advice would be appreciated.

Best regards,
Dave T.

 

[MikeHalloran]

Why are you releasing the hydraulic pressure when you don't want the load to drop?
What did you think would happen?
What do you wish would happen, or not happen?

We would probably develop a better understanding of your problem, given some drawings, sketches, or photos of your apparatus and its operation. Remember we are not there to look over your shoulder; we only see what you show us.



Mike Halloran
Pembroke Pines, FL, USA

 

[DaveGEA]

Why are you releasing the hydraulic pressure when you don't want the load to drop? The pressure is released to allow the electric motor to move the load freely
What did you think would happen? Exactly what does happen
What do you wish would happen, or not happen? maintain just enough pressure in the cylinder to allow the electric motor to move the load. I want to drive the load down.

 

[kiwitom235]

Hello,

What is supplying the hydraulic pressure anyway? Do you use a pump?

How do you 'remove' the hydraulic pressure? Do you simply divert the hose to tank?

Now we have established the mechanical aspect of the situation, we need the hydraulic side of the story. What valving etc is in place? Can you provide a hydraulic schematic for the hydraulic system?

Tom

 

[DaveGEA]

What is supplying the hydraulic pressure anyway? Do you use a pump? Yes Pump

How do you 'remove' the hydraulic pressure? Do you simply divert the hose to tank? electric solenoid valve controlled by the operator dumps to tank

Now we have established the mechanical aspect of the situation, we need the hydraulic side of the story. What valving etc is in place? Can you provide a hydraulic schematic for the hydraulic system? see picture

 

[hydtools]

So you want to maintain some sort of preload. Add an accumulator to the cylinder hydraulic line. It will make the cylinder act like a spring always preloading the slack out of the screw.

Ted

 

[DaveGEA]

do I also place a regulator between the valve and tank?

 

[hydtools]

What do you want the regulator, I assume pressure control, to do?

Ted

 

[DaveGEA]

correct; I need to lower the pressure to prevent the motor from overloading when lowering the load. i tried to lower the line pressure but when I do I am not able to take up the backlash after the pressure is applied.

 

[hydtools]

If you size the accumulator, the pressure change will not cause an overload for the motor. The accumulator cylinder combination would provide a counterbalance for the die weight reducing the load on the motor through the screw travel if the accumulator is sized to produce a pressure change range due to hydraulic volume change that does not overload the motor when the die is seated.

Ted

 

[John2025]

Adjust the pressure so that it will maintain enough pressure in the lines to remove backlash, but still be able to move the load with the motor?
If you still want to release most of the hydraulic pressure to move the motor then consider adding a check valve installed "backwards" in the return line. There's a fixed pressure required to operate the check valve and that will maintain a residual pressure. I've seen check valves stacked in this manner to increase the residual pressure. Each check valve adds a pressure increment. My recollection is that each check takes about 100 PSI to open.

 

[DaveGEA]

Thanks John and Hydtools, I will use a combination of both of your advise.