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Shop built press brake... New to me. Hydraulic guidance please

TFPace

Stainless
Joined
Oct 11, 2003
Location
Pinnacle, NC USA
The guys in VFD, x- formers forum were very helpful in getting the A-B starter modified.

I'm hoping you guys can assist with a hydraulic question I have work this press.
The history on this press is that it's 30-ish years old. The guy that built it is dead so I'm having to rely on you guys for hydraulic expertise [emoji6] .

From the pictures I'm attaching you'll see three cylinders. There is Rexroth valve of some sort that is part of the piping. These three cylinders are piped in parallel.
The wiring is very simple. Up and down pendant with an up/down, EPO switch and power switch.
There are limit switches for up and down too.

My problem today is that I can't get the cylinders to raise or lower. The valve is operating correctly.
What is the blue Rexroth valve do? thanks
We disconnected the piping and reconnected into correctly.
The darn thing just won't budge. I don't know if it has as air lock or something?
The pump is a 20HP.

Any ideas as to what I may be missing?

Thanks,

Tom
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At the risk of being Captain Obvious is the pump running the correct direction?


John,

Thank you for question. Using the last photo that I posted as a reference the motor is rotating CCW. I am tempted to reverse it and see if this helps. The blue valve up top may very well be one direction only.

Tom
 
Sixth photo down looks like solenoid valves. You should be able to pop the covers and manually activate them. The spools (? not sure the correct term anymore) in the valves can get icky inside and not open or shut.

A pressure gage on the system would help, too. That will also tell you if the motor is going the right way. Should be an arrow marking on the pump tho, as mentioned.

And you should probably bleed the system. Hydraulics don't like air.
 
The motor is turning in the correct rotation.

Other than switching the hoses I don't know what else to do. They were color coded so that's easy. I failed to say that they shop this came from had no power so I didn't see it operate [emoji6]

I'm certain lines are full of air. There's a spare plug on each cylinder that I can open to bleed the air off.

Thanks guys.

Tom
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Correct hydraulic pump rotation O.K.... I have to ask I am sorry but is there enough oil in the sump/tank?
The Rexnord could be a pressure relief, it has a cartage on top. Does the smaller hose go to sump or a return line?
On the outlet of your Ducdo vane pump there appears to be an adjustable pressure control (black knob) just after that there is a tee with a plug I would pull the plug and install a pressure gauge that reads at least 3000 psig if all is well with the pump and outlet pressure control than you should see working pressure at the gauge when running. If not then just for giggles check the pumps pick up/ suction screen (if it has one)
If still no pressure then pump/pressure relief problem. If it has pressure but no function then check your hydraulic flow control circuit out.
The vane pump will pull its own prime, if all is correct it will push any air that is in the system out on its own after a couple of machine cycles.
Your hydraulic tank and pressure control look a lot like very early oil gear company components.
The press looks very well made.
Just remember that once you get this press going that you will always want to press from the center of the press out.
Example if you were to press a 50 inch long sheet you would want to have 25 inches on either side of the center of the ram/apron. With the 3 hydraulic cylinder system you have , pressing a short piece on either end will cause the hydraulic ram on the opposite end to travel faster as there is no load(path of least resistance for hydraulic pressure) Tilt, this could be hard of what ever type of ram guides that were made for this press as it could side load a little until it bottoms.
Hope this helps
 
I'm with dana gear, blue valve looks like pressure relief. Was the pump built for this press? If not, might be another pressure relief valve somewhere on the pump unit, too. I'm guessing that's why they put that blue pressure relief valve way at the top, so regardless what pump the press got hooked to, it wouldn't see hydraulic pressure higher than the builder of the press intended. Have you checked to see if your limit switches are moving freely and functioning?
 
I'm guessing it's your solenoid valves not working though. It wouldn't take hardly any pressure at all to move the ram up and down while not pressing anything. So even if the pump is weak, it should still move the ram some if the pressure can get to the cylinders.
 
I'm with dana gear, blue valve looks like pressure relief. Was the pump built for this press? If not, might be another pressure relief valve somewhere on the pump unit, too. I'm guessing that's why they put that blue pressure relief valve way at the top, so regardless what pump the press got hooked to, it wouldn't see hydraulic pressure higher than the builder of the press intended. Have you checked to see if your limit switches are moving freely and functioning?
Hello Homestead and Dana Gear

The limit switches do work. But they aren't keeping it from moving. The upper limit was keeping the press from a down stroke. I adjusted that and the valve opens for up/down.
When I press either the up or down switch the lines are moving and shaking . I'm getting leaks from too so I know getting pressure.
Having air in the system. Wouldn't the air just move on through? I can try to purge the lines.

There's a pressure gauge on it. I'll attach a picture. It's in a rectangular box. Needless to say it's cold [emoji15] .
The tank is half full.

I did contact Rexnord and learned that that valve division was sold if years ago.
A company in Ohio took it over and they hadn't replied to my email. When I called​ the business I was greeted with a strange voicemail​ system.

When we actuate the switch, of the three cylinders the only one the attempts to move is the third cylinder. The farthest from the pump.

Thanks guys for your excellent advice and guidance. I really appreciate the help.
Wood splitters and farm implement hydraulics is all I know [emoji3]

Tom

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I'm guessing it's your solenoid valves not working though. It wouldn't take hardly any pressure at all to move the ram up and down while not pressing anything. So even if the pump is weak, it should still move the ram some if the pressure can get to the cylinders.
If the valve is energizing in both directions could one side still be stuck?

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The gauge is made by Schrader. 700 psi on either the up or down stroke.


The tank has a capacity of 110 gallons. The tank has 43 gallons in it now.
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I would try bleeding the system of air. Maybe to the point of installing a valve to bleed the air off.

My hydraulic planer is getting on in years and after sitting overnight there is air in the system. Until the air is removed all the controls act weird. Once it is warmed up, and I bleed off the air by way of two bleeder valves on the main cylinder and two valves on the clapper boxes, everything settles down and works as it should.
 
I'm not real well versed in solenoid valves, as most of the hydraulic stuff I work on is mechanically actuated, so I'm not exactly sure how they've got that valve set up. The hoses shaking and a cylinder wanting to move a bit gives me the impression that flow is getting to the cylinders but can't get back to the sump. Does the pump unit disconnect from the press via quick connects? If so, try flipping them around. Shouldn't make any difference other than making the pendant controls opposite of what they should be, but you never know. I also don't think that air is the main source of your problem. I've never had a machine get "air bound" and not work at all until the air was bled. If there's air in the system things will work a little weird till it all comes out, but it always comes out on its own in a system like this. Anything is possible though.
 
I'm not real well versed in solenoid valves, as most of the hydraulic stuff I work on is mechanically actuated, so I'm not exactly sure how they've got that valve set up. The hoses shaking and a cylinder wanting to move a bit gives me the impression that flow is getting to the cylinders but can't get back to the sump. Does the pump unit disconnect from the press via quick connects? If so, try flipping them around. Shouldn't make any difference other than making the pendant controls opposite of what they should be, but you never know. I also don't think that air is the main source of your problem. I've never had a machine get "air bound" and not work at all until the air was bled. If there's air in the system things will work a little weird till it all comes out, but it always comes out on its own in a system like this. Anything is possible though.


I'm very tempted to switch the lines too. I can't think of anything that it could hurt. Burping may be the answer.
 
The ram(s) are free ? The crossbar is not bound up in any way ? If the lines are jiggling and shaking, it seems like something is going on. If there is pressure on the piston, it's going to want to move ... unless the mechanism is locked up or frozen in some way.
 
The ram(s) are free ? The crossbar is not bound up in any way ? If the lines are jiggling and shaking, it seems like something is going on. If there is pressure on the piston, it's going to want to move ... unless the mechanism is locked up or frozen in some way.

SeaMoss,

The crossbar does move up & down albeit very slightly. To free all three cylinders from the crossbar would be a difficult task. There is one outer cylinder that needs re-packing though. The center cylinder is a monster.

I can't definitively say the crossbar is free yet.

Thanks,

Tom
 








 
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