Hydraulic Flow control valve

[Egan]

Could a hydraulic flow control valve be used to control the speed of the ram? If yes I’m guessing it would go between the pump and main valve?

I’m planning on getting two, 4.5” bore hydraulic cylinders which should give me 47 - 48 tons, what size pump, motor, oil reservoir etc do I need?

What is the best way to set up your press in terms of valves. One that automatically raises the ram up or one that you have to manually tell the ram to go up or down? I think Big Blu presses automatically make the ram go down when you let your foot off the pedal but it futures adjustable limit switches which stop the ram wherever you want.

[Caleb Gant]

I believe ram speed is generally dependent on gpm through the cylinders. If your running a 3 phase motor connected to your pump than my understanding is that you can speed up or slow down the ram speed by controlling how much hydraulic fluid is going through the system. I’m sure there are hydraulic control valves out there that control the flow speed as well as the flow direction but I would imagine those are more expensive. You could also in theory put a flow  control valve in between your main directional control and your resovoir/pump I don’t know much about that  but hydraulics and pneumatics generally work off of the same basic principles so I would imagine that would work.

[Frosty]

Welcome aboard Egan, Caleb, glad to have you. If you'll put your general location in the header you'll maybe get to network with members living within visiting distance.

The short answer Egan is, Yes. There are a number of ways to do this, a flow restrictor will typically be placed in the circuit between the control valve and the tooling: ram, motor, etc. 

You can buy flow restrictor control valves, either preset or adjustable but this is crazy expensive by comparison to just buying an inline restrictor valve. 

What kind of control valve you want is a matter of preference. I prefer detent valves so the tool stops where I want it to rather than one that automatically reverses. (sorry I can't recall the correct term and I worked with and on hydraulics for more than 20 years)

Most guys want the ram to return home when they release the control lever / peddal / whatever. This is a good set up, you can release it and go do something else without having to think about or preposition the dies. It just returns home and waits.

I like the ram stopping when I let go of the valve, that way I can leave the dies open JUST ENOUGH to fit the piece I'm working on so there is no losing heat while the die closes for the next press. There are disadvantages though, I've tried to insert the next piece and discovered the die is where the last piece was so I have to raise it. 

Plusses and minuses to everything you know.

Caleb: You're pretty much right but it makes no difference what kind of motor drives the pump: single, 3 phase, gasoline, diesel, water wheel, windmill, or slaves on a capstan.  RPM to the pump determines GPM within the pump's ratings. Torque to the pump determines PSI again within the pump's ratings.

I believe I addressed your other thoughts above, if you have more thoughts or questions give me a shout, I'll do my best to answer them even if I have to go upstairs and dig out my books.  

Hudraulics and pneumatics are fundamentally the same but with one fundamental difference. liquids are incompressible and gasses compress. There are some serious differences inherent in the simple difference. Blow a hydraulic fitting and unless you're standing within a few inches it's unlikely you'll be injured, covered with oil maybe but undamaged. However, if you blow a pneumatic fitting pieces can be blown across the shop at bullet velocities. Release the pressure on hydraulic systems and it drops to zero almost instantly where pneumatic systems have to depressurize the whole system connected by an open valve. 

Frosty The Lucky.

[Irondragon Forge ClayWorks]

Frosty pretty much covered it.

I suggest that ya'll read this to get the best out of the forum. READ THIS FIRST   It is full of tips like editing your profile to show your location because so many answers require knowing where in the world you are located. Other tips about how to do the most effective search and many links some which will help in flying under the moderators radar.

[Egan]

Thanks Frosty,

I already have this flow control valve and plan on using it. I believe it can handle 0-30 GPM. Would using a 2 stage pump that runs 30 GPM or something close to 30 at the high end be best so I can have a fast press but have the ability to slow it down if that’s too fast? 

Second, my understanding is there are 3 configurations for how to control the ram.

1st, you manually have to make the ram go up and manually have to make the ram go down. (Which is the configuration you like)

2nd, A detent valve where wherever you put the peddle, handle etc it stays there. (Which would seem to me you would have less control)

And 3rd, a mix between the 1st and 2nd configuration. Where when you release the peddle the ram goes up until it can no long go up. (I assume you use a spring rather than a detent valve but place a second spring somewhere that would pull the handle up constantly which in turn would make the ram go up without actually manually telling it to? or is there a special valve you use for this configuration)

Wouldn’t this 3rd configuration be a bit annoying, every time you come back to the press you have to wait for the ram to come all the way back down to your work piece. Which brings up another point, limit switches. I’m thinking the “Ultimate” setup would be the 3rd configuration but with an adjustable limit switch to stop the ram from going to far up everytime.

Thanks! 

Egan 
 

 

[Goods]

What you may want to look for is a manually operated 4/3 block center directional control valve or A/B blocked with P to T. Both spring return to center. My terminology may be of a bit on the 2nd one. Be very aware of the center porting. Porting wrong and it could be dangerous (lots of ways to may it dangerous actually), but putting the pressure back to tank may save strain on your pump. It’s been a while since I’ve spec’d hydraulics out myself.

Keep us posted on your progress,

David

[Frosty]

Egan: If you already have your press controls planned why are you asking question about valves?  You can't plan a complex hydraulic circuit without knowing how the basic components work. Sure I'm picking on you a little, we all do this kind of thing, design devices and machinery without really knowing how it works. It's a human trait, we've (yes, Frosty speaks for the whole human race) been doing this for probably millions of years. Look up the "Dunning Kruger" effect if you're curious. We all do it, it's a very blacksmitherly thing. 

I didn't mention detent valves because they are dangerously inappropriate for a home built forge press.  

3rd. option? You want to build your own control valve or pay to have one custom built for you? One with LIMIT SWITCHES?      You're making a joke right? 

Do you know what a 2 stage pump does? Just in case, I'll make what I THINK is a safe assumption the answer is no. A 2 stage pump has a high volume side and a high pressure side, those are the stages. If you put a flow limiter on a 2 stage pump it WILL automatically engage stage 2 and deliver high PRESSURE not volume. It'd be just like driving a car with the automatic transmission in LOW all the time. 

If you spent the money on a 2 stage pump leave a clean circuit and let it do what it's designed to do. Just use an auto returning direction valve and you won't have to figure anything out to make it work.  

To alleve your concern about letting the rams resting retracted with the hydraulic pump running, I'll let you in on how hydraulic control valves are made. Simple control/direction valves like almost everybody uses on a forge press have built in valves called "relief or bypass valves" the circuit is internal to the valve body and is called "relief over bypass." The direction valve used to control a simple two way piston directs fluid to one of two paths, opening the other path to return through a third, larger path returning fluid to the reservoir. When the  valve is in neutral the path to return is open. When the piston is bottomed out but the direction valve is left engaged the bypass valve opens to return fluid to the reservoir. 

It is NORMAL procedure to place the control valve in a safe position and let the pump drive fluid over bypass to warm the fluid and system. 

I hope you didn't take the ribbing personally, it's to help you out of the human habit of inventing things we don't know about. My advice, seriously, follow a set of plans. Do NOT try and figure this out, you'll lean how ad what the components do following a set of plans and  MUCH faster than reading about it online. You have no idea how many hydraulic manufacturer and dealer sites I had to sort through before finding the couple simple terms I was looking for. Without having a decent base of knowledge you have NO WAY to know what's useful build info and what's marketing hype. It's mostly hype.

 Frosty The Lucky.

[Caleb Gant]

On 4/24/2020 at 2:30 PM, Frosty said:

Caleb: You're pretty much right but it makes no difference what kind of motor drives the pump:

Glad to be here! thank you for explaining that to me. I've heard alot of differing info so that helps clear things up. 

[Frosty]

You're welcome Caleb, it's my pleasure. It also feels good that some of those 20 years is good for more than retirement and bennies. 

Frosty The Lucky.