Want to build a cnc Backguage

[AKFALAR]

We have an old 60-ton press brake. I would like to make a cnc backguage for it. Probably just the backguage axis and the height in the form of an electric motor control.


Any ideas on:
hardware
Software?


Thanks

[Al_The_Man]

I have retro-fitted the electronics with a both a PC based design using a 1 or 2 axis Galil card, and a stand alone system using a maple OIT.
Of course you dont need G-code programming for a break or a shear, For the mechanics you could reverse engineer from a present system, they all use a little bit of a different method, the obsolete DynaBend used a rolling ring drive with a linear scale instead of a ball screw with an ecoder on the motor which is the more common method.
For the height gauge it is usually done with a linear scale and interrupts the hydraulic valve when at the programmed height. On the PC based systems I used a 10.1" LCD screen to keep it compact, with the PC in the Pendant.
A typical commercial price on just a back gauge with no height control is around $14,000
Al.

[One of Many]

Originally Posted by AKFALAR We have an old 60-ton press brake. I would like to make a cnc backguage for it. Probably just the backguage axis and the height in the form of an electric motor control. Any ideas on: hardware Software?

If you want it all programmable, then you will need to go with a PC or PLC based system as Al notes. Software in either case would be a custom application, as I see it. Don't know of any off the shelf at least. There are sequential punch press roll feeder controllers that may fit the bill for at least a single axis.

The basic design will depend on the width of your machine. As in dual or single arm. Dual screws for the X(bend line) and R(Rise from the bed) can get pretty complex. Making them stout enough to withstand the occasional slamming of sheet will be essential. Independant ball screws or a limitations with a common motor driven through a jack shaft between the two arms.

Having dual independant screws will allow options like bend lines at an angle. Writing your own software can be an option to create screen form Gui to fill out multiple axis postions for each step if you have the experience(wish I did).

Control methods may take on a different approach. Where acme screws and simple closed loop motion is used, preferably with a compensating nut. It is advisable to always have the ending position on a forward move with speed ramped down to stop at a repeatable position. Common with short moves to back off and creep forward to the new postion. Ball screw and servo systems won't normally have these constraints.

The structure and slides I have seen cover a pretty wide array from jokes to overkill. Your particular application in immediate needs verses what opportunity for more complex work should be part of this decision. Buget may be one issue, but building it twice for the sake of saving a couple bucks now is penny wise, but pound foolish as the saying goes. A good invenstment in one portion of these systems as a foundation will provide something to build on later, rather than a total replacement.

The controller itself does not need to have any fancy options like gearing, interpolation or cutting machine type motion capability. Simple sequential programmable point to point positioning with a possibility of a relay for spring set brake controls. In either 1 or 2 axis and/or addressable helps.

I'm thinking of building one myself if I find the need, time and parts laying around! I have a press brake, but don't use it much. LOL!

Maybe Al could give more details on his endevours? Pluses, minuses?

DC

[ViperTX]

Seems that the backguage would be pretty simple, you would need an extension table to hold up the guide rods or rails and the cast iron backguage. You'll need a hefty center acme screw or ballscrew....probably 11/2 inch diameter. I would also consider some sort of dashpot arrangement to soften the blow to the backguage from an agressive feeder. Simplistically you could use an input screen where you entered the backguage settings either via a keyboard, a decade switch arrangement, etc. This could all be driven by a single board computer (PIC or ??).

You didn't mention any tolerange or range of setting?

[Al_The_Man]

A couple of pic for starters from the last project.
Al.

[One of Many]

Sweet!

What was that, an old Hurco gage control box that you used there?

Very nice clean setup.

DC

[Al_The_Man]

The original was a DynaBend, I used a PC based system using a single axis Galil card, AMC servo amp and used the original DC motor, The software was an old product of Galil called Opint, they no longer sell it, but it is excellent DOS based software for simple types of machinery, but at the time it was a one time buy, and you just purchase a hardware key for the board for $200.00, (they still will supply the key).
This BG was the one that had the rolling ring drive,the only one I have seen that uses this method, it works pretty good.
Al.

[One of Many]

Oh, yeah. Dynamic Research put those out in the early 80's. They became the main after market add on controller for hydraulic presses since they also had programmable ram reversal. Was that press a Diacro/Acroform?

Did you incorporate the ram reversal with any speed changes into your controller too?

DC

[Al_The_Man]

I dont remeber who the break manuf. was, but this one only had the B.G. no ram control, but I have used it for others that do, and also for other applications that use hydraulic servo valves.
Al.