October 24, 2002
Carefully planning the forming order can make even the most daunting project less complicated and problematic.
"What the ...? This can't be done!"
How many times have you heard that expression? Or seen someone scratching his head in bewilderment when trying to decide which flange to form first or last, not unlike the operator pictured in the lead photograph?
Sure, we've all been there, but before we encounter this problem again, let's look for some viable solutions. Where do we start? With the blueprint, of course.
Review the blueprints, either customer prints or flat-pattern prints from a CAD system (or both), and compare them to the actual workpiece. Once you are sure they match, the fun begins. Start by marking the actual part with bend lines and dimensions as shown in Figure 1.
For example, show upward-bent flanges as solid lines and downward bends as dotted lines. The marked part will be used for forming reference at the press brake. Second, do a line drawing to scale on a separate piece of paper, excluding the dimensions (see Figure 2).
Now use your tooling profiling stencils or the actual tools themselves to find the strongest punch profile available that will achieve the desired results. The strongest punch profile is the punch that will handle the most tonnage and still be able to produce the part. In other words, don't use a gooseneck punch if it isn't necessary. Over time, selecting punch profiles by this method will save tooling life, adding years to the tooling and dollars to the bottom line.
Once you have selected the punch profile by matching tool profiles with the line drawing, note the direction the punch is to be placed in the ram (gooseneck facing toward you or facing away). Then add that information to the setup sheet for future reference.
Because we now know the ideal punch profile and which bend needs to be made last, it is relatively easy to decide the remaining forming order. Note whether the V die needs to be toward the front or back (assume double V or quick-change V die) of the piece.
At this point you must decide which toolholders and die bolster are to be installed into the press brake (see Figure 3). This is done using exactly the same process as the punch profile selection.
Seems pretty simple so far, but what about gauging? Do you need to work around special features? Will the backgauges enter the die and punch space? This is the time to refer to the set-up piece that you marked with direction and forming order.
Begin with step 1 and mentally work through the part, placing the stops in position for each step in the forming process and noting whether there is interference with the tools. If there is interference, you may want to vary the height or location of the backgauge. You might even find that thinner material extensions are required.
In rare cases you may find that the V die needs to be placed in the press brake differently. Changing the V-die placement should be uncommon, if you truly have thought through the selection phase.
On some occasions you might need to make the first of two 90-degree bends at 45 degrees, the second at 90 degrees, and then rehit the first to 90 degrees. However, this is a rare, extreme situation.
You guessed it. Try the set-up piece, either an extra set-up part or the one that was marked with the solid and dotted lines, though it is best if you keep the marked piece for direction and forming order reference.
As always, "dry run" (without a part) the press brake to make sure all the data is correct, the press brake has been origined correctly, and that you're not going to form the backgauges.
From there, form up a part, check it, adjust it, record the setup for future reference, and commence production.
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