Hydraulic vs Direct mechanical power transmission?

[DennisCNC]

Any one here see any info related to comparing a hydraulic and mechanical power transmission efficiency?

For instance a electric motor is driving a hydraulic pump, a cylinder connected to the pump with a reversing valve is moving a press up and down.
This is just a example, but how much more efficient would it be to have the electric motor with some kind of crank doing the same things, I know transmitting hydraulic fluid is easier but if it eats up a lot of energy it might be worth looking in to direct mechanical drive?

Thanks

[Geof]

Rather than considering a crank mechanism do a bit of Googling on roller screws for press applications.

There was a thread about a year ago that discussed roller screws quite a lot and gave some links to commercial manufacturers.

A different (better) kind of screw

I think they are used in place of hydraulics and they do have a much higher efficiency.

[DennisCNC]

That would work great if the motion didn't need to be reversed every 2-3 sec.

[Geof]

Originally Posted by DennisCNC That would work great if the motion didn't need to be reversed every 2-3 sec.

Roller screws, like ballscrews, can be reversed much more frequently than that. Your limit depends more on the inertia of the drive motor than anything else.