increasing hydr pressure at end of cyl stroke

[bradphillips]

I have a hydraulic assembly machine which currently utilizes a 5 inch bore x 48 inch stroke hydraulic cylinder operating at 750 psi (maximum pressure from pump) and approx 41 gpm.
Is it possible to "boost" the pressure the last inch or so of stroke by adding valves and booster cylinders that would be triggered by a limit switch? I need to double the pressure to 1500 psi for the last inch or so of stroke.
If the cylinder speed slows down this would not be a problem.

 

[Chapstick]

It can be done may ways.. IMO the best way would be to replace the cylinder with a Fabco dual stage cylinder.

http://www.fabco.com

i think is their site. It will cost ya some but probably a wash considering engineering time and extra cyl's and valves. I use them a lot on hot stamping presses where i need a fast stroke and high pressure at the end of stroke. It's what these cyl's are designed for.

 

[Chapstick]

here is the correct addy, sorry

http://www.fabco-air.com/airpress.html

 

[bradphillips]

Chapstick,
I have used fabco cyl before for stamping also and it worked. But the 48 inch stroke in an assembly application is not feasible with Fabco type cylinder. Is it?
Thank you for response.

 

[EdDanzer]

You could use a horse power compensated pump or a 2 stage pump to allow more flow at lower pressures and lower flow at higher pressures. 2 stage pumps are commonly used on wood splitters and HP compensated on excavators.

 

[Chapstick]

bradphillips,
you are correct, my bad... been working on a project that made me brain dead yesterday and i overlooked the 48 inch stroke, sorry. I'm more of a pneumatic guy myself. What is the limiting pressure factor of your current setup? ->The max pressure your pump will generate or the internal pressure the cyl is rated at.

 

[Mandrake22]

I will second the 2 stage pump suggestion.
Each stage would supply +/- 20 gpm at 750 max psi so the motor load would be the same. When your "boost" portion of the stroke is needed, the 2nd stage could then bypass its flow back to tank. Then, all of the motor power is put into the first stage which would be capable of developing 20 gpn at 1500 psi. The second stage is tee'ed into the discharge piping from stage 1 with a check valve to prevent "boost" pressure from going to tank.
Some of these pumps have a common suction port which may minimize changes to suction plumbing.
We use this system on one of our machines used to compress food and paper processing waste for moisture removal.

 

[budt]

Use a motor flow divider and dump half the flow to tank when you want double pressure. This is a modified dual pump circuit I have used for applications such as you describe. This will add some noise with some types of flow dividers such as gear types but gerotor types are fairly quiet.

Another option is to use a cylinder with a 2:1 area ratio as an intensifier and a sequence valve to bring it on line when a reaching a preset pressure. This can only be used for short high pressure strokes but I have used it for punching operations with great success.

Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us