DIY Press Brake, have problems, need help?

[jlansaw]

So I decided I needed a press brake. I purchased the 40" press brake builder kit from Swag Offroad and fabricated a frame for it. I planned on using two HF 20T air/hydraulic jacks to power it. I plumbed both jacks to a "T", using one valve to control the air to both. My first test after assembling everything revealed one jack works faster than the other one. I can't get them to work at the same rate. The left jack always rises faster than the right jack. Can anyone tell me if there are any adjustments that can be made to these jacks to correct this?



BTW, I put a regulator inline on the left jack and tried to slow the jack by regulating the air but I couldn't get any consistency. Also, manually controlling the jacks, they move equally. This makes me think the difference is in the way the air motors are controlling the jacks.


So close to being done with this. Very disappointing to make it this far and have issues.


Any help is appreciated,

Thanks,
Jeff

 

[matt_i]

This is a problem on a large press brake which has two hydraulic cylinders. There can't be a simple tee on the hyd fluid side as the ram with the lesser force will get more of the flow, leading to a non-parallel punch & die. What I have seen is there is a flow divider which positively gear-pump coordinates the flows to both cylinders on the 'press' stroke. On return it doesn't really matter.

In your case I would investigate some way of controlling the length of the pump-piston travel on the air-side with a jam-nut setscrew. By tweaking around with that you should theoretically be able to arrive at a setup which pumps the same amount of hydraulic fluid to each piston.

 

[EdT]

When you're actually bending something, you'll want the air pressure to both jacks to be the same since, I think, the hydraulic pressure from the jack is governed by the air pressure so they need to be that same. I think what you need to to is control the air flow to get the pump speeds matched. If I was faced with the problem, I'd try putting a flow control needle valve into the air input of both pumps. For now, try reducing the air flow to the fast pump with the flow control on the other pump wide open. As things wear and change over time, you will probably need to adjust the flow on one or both pumps to keep them in synch. Long term, you may find it simpler to get one cylinder and one pump of sufficient force . The synchronization issue would go away with a single cylinder. I am assuming that your compressor is not taxed by this application. If it is, the pump nearest the compressor may be hogging all the air and the other pump is starving. Unlikely, but possible.

 

[jamscal]

Not related to your current issue but you're going to bend your die if you don't have more below it for support.

(unless I'm missing something in the pic).

 

[jlansaw]

Not related to your current issue but you're going to bend your die if you don't have more below it for support.

(unless I'm missing something in the pic).

The picture is just a mock up, I have several more plates to put under the die when and if I get use it.
Thanks,
Jeff

 

[cooljoe57]

A flow control valve should fix your problem.

 

[Provincial]

First try removing the valves from the air hoses. Then put a T fitting tying them together with the hoses attached to the cross-bar outlets of the T. Then put one of the air valves in the center of the T. This will apply air pressure/flow as evenly as possible to both jacks.

It may help, but mostly it is to check if the jacks move equally if supplied with equal air flow.

Harbor Freight sells products made by different factories, and even different suppliers, with perhaps a different product number, and perhaps even under the same product number. You may have jacks that are not identical, even though they are both rated at 20 tons. If you still have the packaging, check to see if they have the same SKU number.

 

[jlansaw]

Is it possible I don't have enough cfm to operate two jacks at the same time? I haven't tracked down the cfm spec for the jacks or the compressor but it makes me wonder?

Jeff

 

[Rccrawlerguy]

Here is an option that would help you get even bends, but not solve the issue with jacks operating at different rates. Mount a tape measure or scale to each of your presses vertical member and make a pointer. Or have you seen the iGaging digital read outs? Mount one of those on each side, and still keep your jacks seperate, and just run each side until you get the desired bend.

Nice thing about using the DRO's is that once you bend lets say 1/8" plate to 90 degrees, you will be able to take note of the distance the punch has traveled down.