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Old 03-18-2017, 09:40 PM   #1 (permalink)
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DIY Press Brake, have problems, need help?

So I recently built a press brake that uses the 40" Swag Offroad finger brake. I made it with 2 HF air hydraulic 20T jacks. The problem I'm having is synchronizing the jacks when controlled by air. One extends faster than the other causing the die to compress unevenly. Anyone had this issue? Are there any adjustments that can be made to the jacks to match them up?


Any help is appreciated.
Thanks,
Jeff
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Old 03-19-2017, 02:21 AM   #2 (permalink)
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Maybe an air pressure regulator on each ram, to try to tune the speed of each? Or just on the faster one....

Trying to synchronize two rams seems like a nightmare to me. Especially air/hydro ones.
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Old 03-19-2017, 07:23 AM   #3 (permalink)
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Maybe an air pressure regulator on each ram, to try to tune the speed of each? Or just on the faster one....

Trying to synchronize two rams seems like a nightmare to me. Especially air/hydro ones.
I threw a cheap regulator in line on the fast side and couldn't get any consistency. By the time I got it adjusted the cycle was over. The next cycle requires more adjustment and so on.

I saw various pics of this type of setup on the on the web including units done by Swagoffroad. Nothing I read mentioned any issues with using 2 air jacks. I figured if there was a problem there would be threads everywhere discussing the issue. Guess I was wrong. It may be "back to the drawing board"

Jeff
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Old 03-19-2017, 08:08 AM   #4 (permalink)
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http://www.pirate4x4.com/forum/shop-...1040810?page=4

I don't remember all the post numbers, but go to #25, and you'll find what I'm referring to. Might work? Might be a PITA though too....
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Old 03-19-2017, 02:57 PM   #5 (permalink)
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What about useing a bull head t then use 2 equal length lines then put an orifice in the line . I've had to do air control lines on propane bulk plants like this .
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Old 03-19-2017, 06:03 PM   #6 (permalink)
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Today I put air to each jack individually. Timed the complete cycle of each jack. There is about a 6 second difference in the cycle time. Took the air motors apart, inspected, cleaned, reassembled. Timed again, same results. Put a level across the jacks, raised the jacks manually together and with equal pumps, one was rising faster than the other. Very frustrating. Not an issue until you try to get 2 jacks to work together.

Jeff

Last edited by jlansaw; 03-20-2017 at 04:37 AM.
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Old 03-19-2017, 06:44 PM   #7 (permalink)
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Ill bet the pulsing of the air is freaking out the regulator. I would plumb in some sort of an air tank after the regulator with the theory that the air supply will have a better regulated air pressure without spikes. An easier to do test might be to add a 25 or 50ft air hose after the regulator to act as a receiver. If trying with a hose try to use as large diameter hose as possible.
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Old 03-19-2017, 06:58 PM   #8 (permalink)
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Just thought of something..... If you limit air pressure to one Jack to slow it down so that they operate at the same speed.... What happens when is under load? I would assume it wouldn't have as much peak pressure, but will it be proportionate? Ie: no load, they move identically..... but once it hits the metal, will the regulated Jack then slow down due to being under pressured and cause uneven bends?
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Old 03-19-2017, 07:18 PM   #9 (permalink)
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Is it possible to have one air motor drive both jacks? It would take twice as long but would they equalize between the two? Never really looked that close as to how the air motors attach to the base of the jack. Just a thought with no experience.
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Old 03-19-2017, 07:52 PM   #10 (permalink)
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I would share hyd pressure, (cylinders fluid connected) and have some sort of mechanical link between rams. Think like a sway bar design.
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Old 03-19-2017, 08:58 PM   #11 (permalink)
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that

put the faster one on your engine crane
then take the plain old engine crane one and combobulate an external line to it from the remaining air/hydro cyl, if you wanna be real lazy just drill straight up through the bottom of both bases, centered on the ram and tap them NPT

then mechanically link both sides, with a pipe, and a few bits of bar stock for arms and links

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Old 03-20-2017, 03:31 AM   #12 (permalink)
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Possibly a flow meter to each cylinder.. infinitely adjustable.
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Old 03-20-2017, 05:38 AM   #13 (permalink)
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You need a mechanical linkage.
Multiple cylinders, air or hydraulic will never synchronize without very expensive electronic controls.

Lots of threads where guys all had the same problem with their homebrewed press brakes.
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Old 03-20-2017, 06:35 AM   #14 (permalink)
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Hack the cylinders apart and use a rotary flow divider?
Rotary gear flow divider - 2 Section, 2R8.8S | eBay

Not sure if the minimum flow would be a problem though, maybe there is a really small one out there.
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Old 03-20-2017, 09:49 AM   #15 (permalink)
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Possibly a flow meter to each cylinder.. infinitely adjustable.
if you want a cheap way without rebuilding the press head; restrict the flow, not the pressure
a simple globe or needle valve in each air line should do it
a globe or needle valve will have infinite flow restriction vs an on/off ball valve
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Old 03-20-2017, 06:21 PM   #16 (permalink)
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I know it's primitive but can't you just watch the top die and adjust accordingly?
At the local fab shop they have a 10' hydraulic press brake and it's a bitch to keep it in sync. It fluctuates depending on the weather, temperature and who knows what else.

Buy another jack and see if it matches up to one of yours?
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Old 03-20-2017, 09:16 PM   #17 (permalink)
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Quote:
Originally Posted by _ogre View Post
if you want a cheap way without rebuilding the press head; restrict the flow, not the pressure
a simple globe or needle valve in each air line should do it
a globe or needle valve will have infinite flow restriction vs an on/off ball valve
^^^^this^^^^

A simple flow control will restrict the passage way of the air line and thus the speed of the cylinder. I manufacture piston filling machines that put BBQ sauce into bottles, guacamole into tubs, cake batter into pans, etc. and that is what we do to control the forward speed and rear speed of our air powered machines.

A couple bucks and you can tune the two sides very quickly.
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Old 03-23-2017, 08:16 AM   #18 (permalink)
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I would either do one air motor with hydraulics split between the two or a good hand pump with a split line. Counting on 2 china made air products to match or behave predictably sounds like an exercise in 4 letter vocabulary
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Old 03-23-2017, 10:41 AM   #19 (permalink)
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Go buy another one and run it to see which one it is closer to and then return the odd one to the store for a refund.

I'm really surprised that when they get loaded they don't equalize. Something isn't right with one. I'd try swapping it out.
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Old 03-24-2017, 08:43 AM   #20 (permalink)
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Why not use a single 50 ton air/hydraulic jack and beef up the frames a little? Virtually the same price as two 20 ton HF's.
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