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Hello! I have a question about a 4-way directional control valve. I have build a forge press for my smithy, and I’m wondering if there is a power stroke port on my control valve. The system is a 25 ton press, but I don’t feel like I am getting the power that the system is designed for. I’ll attach some pictures. I’m wondering if I have my hoses from the control valve and DA cylinder connected correctly. I installed everything to the manufacturers specifications. Also, regarding the control valve, I have to lift up on the handle to articulate the cylinder downward, and push down on the handle to articulate the ram upward. Can I reverse the hose positions on the control valve ports to reverse the direction without sacrificing tonnage force? Is the force equal on both ports? I think I remember reading something on the cylinder spec that the return stroke is much less powerful than the  pressing stroke. Any help would be greatly appreciated. Than you!! -Joshua Frost

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You can certainly reverse the hoses. The valve doesn't care which end of the cylinder the hoses go to.

What pressure are you running at and what is the bore of your cylinder?

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Unless your cylinder is a thru rod type the force retracting is reduced by the area of the rod itself. From the pics you have a normally cylinder, so if you make a ratio of the rod area to the cylinder area you can use that ratio to calculate the reduced tonnage on retraction. Inverse the ratio and you can calculate the increase in max return speed.

There could be a difference in the valve also, but I would need to see the valve diagram to help out there. A power stroke option would be awesome for a forging press, especially if it has a large rod to bore ratio!

I like the idea of having the action lever reversed. If you hit the lever accidentally the press opening could be a much safer failure mode.

Either way, enjoy the press,

David

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34 minutes ago, Goods said:

Unless your cylinder is a thru rod type the force retracting is reduced by the area of the rod itself. From the pics you have a normally cylinder, so if you make a ratio of the rod area to the cylinder area you can use that ratio to calculate the reduced tonnage on retraction. Inverse the ratio and you can calculate the increase in max return speed.

There could be a difference in the valve also, but I would need to see the valve diagram to help out there. A power stroke option would be awesome for a forging press, especially if it has a large rod to bore ratio!

I like the idea of having the action lever reversed. If you hit the lever accidentally the press opening could be a much safer failure mode.

Either way, enjoy the press,

David

Omg DUH. I can’t believe I didn’t think of the volume of the rod taking up space in the cylinder on the return stroke! Thanks for pointing that out. Now I feel like an idiot. I don’t think it’s a problem with the valve, although I’d love a power stroke option too!!

And I don’t know, maybe the action of the lever is something that I can get used to. Your point about safety is well taken. 

Thanks very much for the reply!!

-Joshua

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Don’t worry, I didn’t think of it as idiotic, just over looked it. I deal with it more than I like.

If you’re your valve has the capability of doing a what “we” call a power stroke (putting pressure to both sides of the cylinder) you could greatly increase the extend speed (if I’m thinking right 6x current extension speed with your cylinder, but only 1/6th of the force). We usually put a limit switch in and use a separate solenoid to switch modes, but one could always use a pilot valve set to switch at a given “back” pressure. The hydraulic diagram can get fairly complicated...

If you try it let us know how it works! I’d love to make a press, but limited electrical service available in my “shop”, not to mention time and money!

Take care,

David

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What is going on with your hoses...they look lumpy which could indicate failure. Pressurized hydraulic fluid is dangerous.

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2 minutes ago, Steve Shimanek said:

What is going on with your hoses...they look lumpy which could indicate failure. Pressurized hydraulic fluid is dangerous.

They are wrapped in protective fire sleeve in case they accidentally come in to contact with hot steel. I thought it was a necessary safety feature given the environment they are operating in. 

-joshua

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It's water under the bridge but you might also check the valve diagram to see if it's center open rather than center closed. With center closed, when the handle position goes into the neutral point, the cylinder cannot move.  With center open valves, you can move the cylinder when it's in the neutral valve position though it's not always easy to do.  That means if something goes awry---like a power outage or popping the breaker or whatever,  with center closed valves you cannot physically move the cylinder to get your part (or hand in some worst case scenario) out.  If it was a large hot part, it's pinched in there heating everything up while you try and chase a problem.  If it's your hand (say for instance you had a cold forming brake die in there and your hand happened to get pinched), you can't move to chase the problem at all--you can only scream for help.

Not a huge deal (until you need it) but one more little safety aspect that might be worth thinking about.

Magnetic starters are nice too (required on bigger commercial stuff).  Again, in a power outage it keeps things from starting back up and surprising you.  Not a huge issue on a press like that but a big issue on rotating equipment like saws or drill presses.  We get a lot of transient outages here--a couple of minutes at a time where it's just long enough to be worth walking away.  Magnetic starters have saved me from my own stupidity many times.

 

 

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