Which press specs?

J

Jason Fry

Knifemaker / Craftsman / Service Provider
Joined
Jun 5, 2008
Messages
3,160
Which is better…

20 ton press at .59/2.16 inch per second low/high

24.5 ton press at .39/1.57 IPS

These seem to be the two best options for a 3 HP motor and a 5” cylinder, best I can tell.
 
Jason Fry said:
Which is better…

20 ton press at .59/2.16 inch per second low/high

24.5 ton press at .39/1.57 IPS

These seem to be the two best options for a 3 HP motor and a 5” cylinder, best I can tell.
Click to expand...
Are you building the press or buying? What is the .59/2.16 in/sec - is that the ram speed at high pressure and low pressure? I'll be looking forward to the experts chiming in, but I wouldn't think the speed at high pressure would be very important since the ram isn't going to move very much at all at high pressure. Only the low pressure speed would be important is my thinking.

The specs I would be concerned about is the GPM of the pump at low pressure, and high pressure and size of ram. You've already mentioned the 5" ram. Here are 3 online calculators I've found handy in playing around designing a press. Remember most hydraulic pumps are spec'd at 3,000 rpm or more. That's why it's important to use a 3400 rpm motor for the press. It's hard to find a pump spec'd at 1800 rpm. The high rpm pump works just fine at 1800 rpm, but much less GPM output.

This one is to determine the tons of pressure for the press depending on ram size and high pressure. I like 2500 psi.

This determines the speed of the ram travel, use low pressure pump GPM:

This one does a decent job of calculating motor hp requirements. Use the high pressure GPM of pump since the low pressure GPM won't take much HP at all to move the ram.
 
Thanks for the calculators, Ken. The numbers above are pulled from Batson and include 1750 RPM and a pump rated for 2x the GPM at 3400.

Building a press this fall if I can sell a few good knives at Atlanta.
 
Well that’s an interesting twist… may have found an affordable 5hp. More calculations to come.
 
It's fun running the numbers on a press. with 5hp you've got plenty of power for even a 30 ton press. 5" cylinder at 3,000 psi is right 30 ton, but at 2500 psi it's 25 ton. You gonna have a NICE press. Have you decided on a "H" design or "C" design?
 
Jason Fry said:
Well that’s an interesting twist… may have found an affordable 5hp. More calculations to come.
Click to expand...
And a 6” cylinder is twice the cost of a 5” cylinder. So much for saving money. Too many choices lol
 
Ken H> said:
It's fun running the numbers on a press. with 5hp you've got plenty of power for even a 30 ton press. 5" cylinder at 3,000 psi is right 30 ton, but at 2500 psi it's 25 ton. You gonna have a NICE press. Have you decided on a "H" design or "C" design?
Click to expand...
I’m kind of thinking C.
 
Good choice if you've got the steel for a C style. I tend toward the "H" style since it's easier to get the steel. BTW, here's a couple more links you might like

This is to calculate the stretch in a beam, perhaps more used for "H" design press? It seems Young's modulus of steel is around 29,000,000
or perhaps this one: https://www.omnicalculator.com/physics/stress#an-example-of-calculations

For a "C" the beam deflection calculator might help.

I've "wasted" many hours playing with these calculators, so have fun :)
 
My dad is a structural engineer, I may let him do all those calculations just for “fun” lol
 
Calculating the stresses on the press will be right up your Dad's alley. Keep us updated on your progress with the press. You've done some wonderful WIPs with your knives, so I'm looking forward to a similar WIP with the press :)
 
Let's consolidate threads here... I just posted this one today, about the same press... Now that I've got a motor on hand, I can purchase the hydraulic parts for real instead of just running hypotheticals.

I have a Baldor 1750 RPM 5 HP motor.

If I go with a 16/3 GPM pump, at half speed, that'll give me 8/1.5 GPM flow rate.

If I go with a 5x12x2 cylinder rated for 3000 PSI, that gives me about 25 tons at 2500 PSI. I think I figured 29.5 at 3000.

With that pump and cylinder, I'll get about 1.57/.29 IPS ram speed.

OR

22/6.5 pump half speed at 11/3.25 GPM
Same cylinder.
Generates 2.16/.65 IPS.

They'll all work, best I can tell. Any reason to prefer one over the other?
 
Jason Fry said:
With that pump and cylinder, I'll get about 1.57/.29 IPS ram speed.
Click to expand...
I wouldn't worry about the .29IPS ram speed, that's only the high pressure part and will hardly ever be over 1/4" distance, and most of time less. The only concern is the low pressure ram speed moving the die from up position to contact with billet, which is where the high pressure kicks in.

Let's see what other folks have to say about the desired ram speed - I'll repeat what I said in other thread, more GPM preferred with the pump for at least 2.5 IPS speed. I doubt you'll tell much (if any) difference between 25 and 30 ton press.

Looking forward to the drawings of the press, AND calculations :)
 
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