On Sun, 22 Feb 2009 22:53:57 +0000, Christopher Tidy
wrote:

Proctologically Violated©® wrote:
Awl --

In particular, how does one size the motor/pump for a given tonnage? Say,
10 tons. Is tonnage the only issue? See below.

My buddy needs one made, is getting a price, but it seems like the price
keeps climbing, and they are claiming he needs 7.5 hp for 10 tons.

We had a Daco 55 ton press, and I'd swear that press had only mebbe a 1-2 hp
motor.

BUT, it operated very slowly.

I would imagine for a *faster* stroke at a given tonnage, hp increases, as
the hydraulic "mechanical advantage" is probably decreasing with increased
speed, so a bigger motor is req'd.

How to calc??

Power = Force x Velocity (there may be a constant involved if you use
imperial units). I figure that using a 7.5 hp motor and a 10 ton load,
you get about 2 inches per second at 100% efficiency. But I doubt you'll
get more than half that in reality.

And you probably don't need maximum force and maximum velocity at the
same time. So you can get better performance using a two-stage pump
which can supply a high flow rate at a low pressure or a low flow rate
at a high pressure and switch automatically between the two.

It's worth noting that an electrically powered press is a lot more
dangerous than a hand powered press. If you're using a hand powered
press and you get your hand trapped in it, you stop pumping because it
hurts. A motor won't do that.

Best wishes,

Chris



Use air over oil, and a small pump to move to the top of the part.

I just completed a 700 ton and a 200 ton ,closed loop, air over oil .

Used a plc and hmi for programming both ramp and target pressure.

Dave B