Author Topic: Hydraulics experts please help  (Read 1717 times)

Offline shipto

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Hydraulics experts please help
« on: May 11, 2016, 04:47:23 PM »
For my next project I want to make a hydraulic powered press similar concept to a Ironworker and making one that will go up and down with a valve should be simple however I would like a semi automatic if possible.
I want to be able to control firstly the up and down manually so I can get whatever tooling set up but once I have it set up I would like to set a pressure and have it return to the start once that pressure is reached.
I have available:
A bank of 3 way valves which I am sure can be split, 2 hydraulic pumps one with electric motor and one fitted to a lister diesel engine, oil tank one single acting ram and 3 double acting rams 2 of which would be a good pair to use for the project and various bits of piping.
electric one is a full built in unit off a raising platform so probably has a pressure limit valve and 3 way valve included will have to look at it closely but its under a pile of other jun... I mean equipment at the moment.
I have done a few searches but am having problems finding the way it is done on the off the shelf presses etc if anyone could point me in the right direction it would be appreciated.
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Offline Sid_Vicious

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Re: Hydraulics experts please help
« Reply #1 on: May 11, 2016, 05:03:12 PM »
Keith Fenner made his own press and have some videos of it on youtube. Maybe you could get some ideas from how he did it.
Nothing is impossible, it just take more time to figure out.

Offline PK

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Re: Hydraulics experts please help
« Reply #2 on: May 11, 2016, 05:09:22 PM »
Stay tuned to the How Do I section. I'm building one at the moment that sounds pretty close to your spec. I just have one problem to solve so I'll be putting pics up in a few days. But I reckon I've nailed the hydraulic aspect of it (from a home workshop perspective)..
PK

Offline shipto

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Re: Hydraulics experts please help
« Reply #3 on: May 12, 2016, 05:49:49 PM »
Thanks both I will certainly look out for your new thread PK and have started to watch the Keith Fenner video's.
dragged the power pack out today was expecting a double ended solonoid but it only has solonoid on side I guess the only way to find out how it works is to put a ram on it and try it. I did search and found packs like it but not the same.
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Offline David Jupp

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Re: Hydraulics experts please help
« Reply #4 on: May 13, 2016, 03:03:04 AM »
The nice thing about a manual valve for the hydraulics is that it keeps one hand out of the danger area, and the hand on the valve is ready to stop things at any moment if things begin to go wrong.

If introducing any automation, think carefully about how best to protect the operator from conflicting with any automated movements.

Online awemawson

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Re: Hydraulics experts please help
« Reply #5 on: May 13, 2016, 05:50:42 AM »
My hydraulic press has electrically operated valves, but operated by a remote button station on a long umbilical cord. It allows me to be out of the firing line  :zap:
Andrew Mawson
East Sussex

Offline shipto

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Re: Hydraulics experts please help
« Reply #6 on: June 11, 2016, 06:09:22 PM »
I have almost completed my press (full build on my blog) and now need to do the electrics and I think I have come up with quite a good circuit although its not totally idiot proof. I thought I would post in case anyone else needs it and in the hope that the drawbacks might get resolved.

s1 send the power either to the "up" footswitch for manual mode or to the relay for the 2 automatic modes.
s6 chooses which automatic mode you need A) press "down" footswitch and it returns as soon as you let go or B) a single press will send press down till it breaks the limit switch then go back up.

As well as this circuit there will be a failsafe pair of limit switches that will feed the stop coil on the pump itself just in case things go wrong.

Just to prove to myself it worked I used it with my variable power supply to bend some metal today and I am impressed by the results. second bit shows a bit of 3mm plate and a bit of 12mm square bar.
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Offline sparky961

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Re: Hydraulics experts please help
« Reply #7 on: June 11, 2016, 06:58:40 PM »
<snip> or B) a single press will send press down till it breaks the limit switch then go back up. <snip>

You may want to reconsider this one in terms of safety.  In working with CNC press brakes, I can tell you that they only close when your foot is on the switch.  You have to hold the switch until the cycle completes the down stroke and any dwell (delay), but it will continue to rise if you let off while it's on the up stroke.

They also have the safety feature where moderate pressure is used on the pedal to activate the cycle but hard pressure on the pedal will move it even more and trip the e-stop, with possibly a retract - can't recall for sure on that one.  Presumably if you get a body part stuck in the machine you're either going to let go of the foot switch or STOMP down on it.  Don't know about you, but either way my preference would be for the machine to stop.

I didn't have a good look at your circuit but you'll want to ensure that a disconnection or failure in your limit switches is fail safe too.  You don't want someone (including you) inadvertently yanking a wire out and causing the machine to start squashing whatever happens to be in the path of destruction.

Offline shipto

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Re: Hydraulics experts please help
« Reply #8 on: June 11, 2016, 07:28:39 PM »
I get the safety concerns but the B) auto mode will only get used for repeat operations like punching holes and as such will only be used for very short strokes. In the case of punching the holes I need the only thing that fits in the jig I made is the 3mm plate so if i make the top of the stroke still inside the stripper bar then there is no chance of a finger getting in the way.

Also the limit switches are closed and open up to stop the stroke so a wire getting pulled free will stop it.

I dont intend anyone else to use this machine so I am just going to have to take care with it.
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Offline shipto

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Re: Hydraulics experts please help
« Reply #9 on: June 20, 2016, 02:45:34 PM »
I knew when I posted the circuit above there was a problem but I couldnt figure out what it was until testing today.
If S6 is in full auto position when S2 is pressed then the limit switch S5 is bypassed and the press can squish the limit switch, so I have updated it with a extra diode to stop this happening.
Turns out this life c**p is just one big distraction from death but a good one. For the love of god dont give yourself time to think.
https://myshedblog.wordpress.com/