Hydraulic forging press build

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Blackdirt cowboy

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Oct 29, 2015
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I’m wanting to build a hydraulic press and I’m starting to gather the materials to get it done. I have a big scrap pile with plenty of metal. I also already have a 10 hp 220v single phase motor I can use. I’m running the calculations on what hydraulic components to get, and I think I may be doing something wrong.

Best I can tell, that motor is good enough o run a 6 GPM flow at 2500 psi and 85% pump efficiency. I was thinking about using a 5”x12” cylinder with a 1.375” rod diameter. When I put this into my calculator, I come up with somewhere around 24 tons, which sounds good to me. But I only come up with a flow rate of 1.2” per second, which is very disappointing. Can someone verify that my calculations are correct. 6 GPM flow doesn’t sound like a whole lot to me for a 10 horse motor. But maybe it’s correct and that’s the best that I can do. I’d like to use a single stage pump if at all possible, and I thought the 10 horse would definitely allow me to do that. But that is the biggest motor I can use, as I don’t have and can’t get three phase power.
 
I run a 5 hp motor at 1725 with a two stage 22gpm pump rated for 3450rpm, which makes it an 11 gpm pump (on the high pressure side). Basically if RPMS go down, torque goes up. I would have to have more then 5HP to effectively run at the rated RPMs for the pump. This set up is just one way of doing it, which allows for a happy medium and cost effective set up. Also, it gives a decent cylinder speed, I don't know exactly what, but 6gpm is probably slower than you want for a forging press. you should be able to get a higher GPM pump that your 10hp motor will run just fine. (
To clarify, pumps are rated for volume, not PSI. So you start with the GPM you want, and get a motor that will handle it with your given cylinder/desired pressing force. (you should be good with a 10hp motor). Therefore, if you run the pump at the rated RPM, it will move that particular volume, or GPM.
Hopefully that made at least some sense!
Important question: is the 6 GPM pump you mention a single or double stage?
You want a double stage pump for a forging press. This means it will run at a certain gpm until it reaches a certain psi (500 I believe. The psi level is controlled by your control valve.) then it will kick over to the high pressure, low speed side and run about 2-3gpm, but up to >3500 psi.
This allows you to run your ram on the press relatively fast up to your work piece, and start forging, and it will kick to low pressure when you really start moving material. This works well, since you don't need the extreme pressure capability just running the ram up and down the rest of the time.
 
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Yeah, I understand all that. But the equation I found is:

HP=(GPM * PSI)/(1714 * efficiency)

So:

10=2500 * GPM/1500
15000=2500 * GPM
GPM=6

Now, I’m wanting to use a single stage pump so as to avoid that split second when the pump “shifts gears” allowing the dies to soak away a lot of heat out of the metal. I also don’t know what the rpm of the motor is. I’m suspecting it’s 1750 as it is a motor I pulled off an auger in my grain storage facility. But I need to check the plate to verify that. Anyway, I feel like the 10 horse motor should handle a lot more flow than 6 GPM.
 
With the two stage pump, you only need to calculate the HP needed to run the low flow side (1.5-3 gpm typically, I think). This is the high pressure side (2500psi) the high speed side runs much lower psi, so the HP requirements aren't an issue. So saying that, 6gpm is a comparatively big number at 2500psi, and probably why your motor (which would otherwise be sufficient) isn't matching up like you need it to.
 
Hopefully that makes sense. I recommend getting Dr. James Batson's book on building a hydraulic press. it's not plug and play plans, but it has the information to understand what you need for the hydraulics, frame strength, etc. I'm sure there are other great plans available from other guys too.
 
Elijah Williams said:
I run a 5 hp motor at 1725 with a two stage 22gpm pump rated for 3250rpm, which makes it an 11 gpm pump (on the high pressure side). Basically if RPMS go down, torque goes up. I would have to have more then 5HP to effectively run at the rated RPMs for the pump. This set up is just one way of doing it, which allows for a happy medium and cost effective set up. Also, it gives a decent cylinder speed, I don't know exactly what, but 6gpm is probably slower than you want for a forging press. you should be able to get a higher GPM pump that your 10hp motor will run just fine. (
To clarify, pumps are rated for volume, not PSI. So you start with the GPM you want, and get a motor that will handle it with your given cylinder/desired pressing force. (you should be good with a 10hp motor). Therefore, if you run the pump at the rated RPM, it will move that particular volume, or GPM.
Hopefully that made at least some sense!
Important question: is the 6 GPM pump you mention a single or double stage?
You want a double stage pump for a forging press. This means it will run at a certain gpm until it reaches a certain psi (500 I believe. The psi level is controlled by your control valve.) then it will kick over to the high pressure, low speed side and run about 2-3gpm, but up to >3500 psi.
This allows you to run your ram on the press relatively fast up to your work piece, and start forging, and it will kick to low pressure when you really start moving material. This works well, since you don't need the extreme pressure capability just running the ram up and down the rest of the time.
Click to expand...

Not necessarily, if he wants to automate a limit switch or repeating cycle, single stage is preferred.
 
I’m not too worried about automating my press just yet. But I think I’ve figured it out. I’m now thinking I do need a two stage press. A 22/11 GPM pump will work well with my 10 horse motor. It will generate 25 tons of force at 2500 psi and give me a cylinder cycle speed of 4.3-4.7” per second.
 
Blackdirt cowboy said:
I’m not too worried about automating my press just yet. But I think I’ve figured it out. I’m now thinking I do need a two stage press. A 22/11 GPM pump will work well with my 10 horse motor. It will generate 25 tons of force at 2500 psi and give me a cylinder cycle speed of 4.3-4.7” per second.
Click to expand...
nice
 
That is assuming my motor is 3450 rpm. If it’s only 1750 rpm, those speed numbers will be halved, and I’ll need to buy a bigger pump to make it run faster.
 
Blackdirt cowboy said:
I’m not too worried about automating my press just yet. But I think I’ve figured it out. I’m now thinking I do need a two stage press. A 22/11 GPM pump will work well with my 10 horse motor. It will generate 25 tons of force at 2500 psi and give me a cylinder cycle speed of 4.3-4.7” per second.
Click to expand...
The other thing I forgot to mention, is without limit switching or automation, you may find a single stage 6gpm too fast for forging under pressure, and difficult to control depending on size of stock, shape of dies, etc.. At least that would be my worry: too fast on the press and too slow on the return.
Anyway, best of luck on the build, a press is a phenomenal tool.
 
That’s an excellent point, and one I didn’t think about. With the 22/11 pump at full speed, cycle time is over 4” per second on the low pressure stage. On the high pressure stage where you’ll actually be pressing metal, cycle speed is 2.2” per second. Do you think that’s too fast to control while actually forging?

If so, I could just down size the pump a bit and it would be slightly over powered with the 10 horse motor. Or I could step up to a 6” bore cylinder and have increased tonnage while decreasing cycle speed some.
 
Blackdirt cowboy said:
That is assuming my motor is 3450 rpm. If it’s only 1750 rpm, those speed numbers will be halved, and I’ll need to buy a bigger pump to make it run faster.
Click to expand...
Blackdirt cowboy said:
That is assuming my motor is 3450 rpm. If it’s only 1750 rpm, those speed numbers will be halved, and I’ll need to buy a bigger pump to make it run faster.
Click to expand...
Have you had a chance to use a press before deciding on speeds and such? If not it would be well worth it. Basically, you want a good speed (but not excessive) on the cylinder return/when it's closing in without pressure. This gives you as much actual forging time as possible. You also want to be able to control it under the high pressure. But trying it for yourself to have a reference point is much better obviously.
 
I don't know, I could
Blackdirt cowboy said:
That’s an excellent point, and one I didn’t think about. With the 22/11 pump at full speed, cycle time is over 4” per second on the low pressure stage. On the high pressure stage where you’ll actually be pressing metal, cycle speed is 2.2” per second. Do you think that’s too fast to control while actually forging?

If so, I could just down size the pump a bit and it would be slightly over powered with the 10 horse motor. Or I could step up to a 6” bore cylinder and have increased tonnage while decreasing cycle speed some.
Click to expand...

I don't know for sure. My press is 11gpm on the high speed side. I could work with a little faster speeds, but I think twice that fast would be too fast. If you do need to slow it down, going with a bigger cylinder is not a bad idea. you won't regret the extra tonnage.
 
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I got the data off the plate on the motor today. It looks like it’s 1710 RPMs. Does this change the way I need to look at this build?

I’m thinking this is the pump I need:
https://www.mcmaster.com/6296K29/
 
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Are you sure about that? These are single stage pumps I’m looking at. So that flow rate is across all pressures. I think the pump you linked will be a little stout for my motor. I read @JTknives build thread and he used a 10 horse motor with a .92 displacement single stage pump.
 
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