complicated workpiece, but each die is a different
height. So the fingers move independently left to
right (Z1 and Z2), as well as up and down (R1 and
R2) to correspond to the die you’re working with.
Some also now use frontgauges for certain applications. Imagine a large rectangular workpiece, 30
in. wide, with a 0.5-in. flange on each side requiring
a 90-degree bend. The 30-in. dimension between
the flanges is critical but the actual flange lengths
aren’t. In this case, you might form the first bend
on the backgauge, just because it’s easier to handle,
then flip the part and put the previously bent edge
against the fontgauge, which is programmed to be
exactly 30 in. away.
Using just the backgauge for this application
would give you two perfectly accurate 0.5-in. flanges. But the 30-in. dimension between the flanges
may not be exactly 30 in. Ideally,
But this isn’t always an ideal world,
and using the frontgauge can help
you maintain that critical dimension, regardless of the variability
you may have from upstream cutting processes.
Many tend to do what they can
to avoid needing a frontgauge because, of course, the frontgauge
is out in front and in the way. But
for certain applications, the frontgauge can work well. For instance,
door manufacturers tend to like the
frontgauge feature because they
care about the door fitting into the
jamb. The width of the side flanges,
though, just isn’t that critical.
Precision of the Ram Axis
Some press brakes now also offer
the Y1 and Y2 axes, which offer in-
dependent control of the ram on
the left and right side. Let’s say you need to make
a 90-degree bend on a 10-ft.-wide workpiece. If the
ram doesn’t come down perfectly parallel to the
die, the angle on either end of the workpiece will
be just a little different. Ram parallelism is accom-
plished in different ways, depending on the press
brake, and controlling each side of the ram inde-
pendently gives you the Y1 and Y2 axes. This kind
of ram control produces extreme ram accuracy,
which can be important for certain applications.
As with any other technology, the application
should drive the machine requirements. A properly
functioning hydraulic press brake typically results
in ±-0.002- to ±0.004-in. tolerance on the ram position between the right and left side of the bed. In
many instances, if the press brake is in proper working order, that variation in the ram position may not
be causing a piece to be out of tolerance. Instead, it
may be due to factors like material springback, material thickness variation, die wear, or improper tool
setup. Ram parallelism off, say, 0.009 in. can cause
many problems in the workpiece. But a ram that’s
off by this much means that the machine isn’t operating as it should.
Related to this, modern press brakes now allow
you to change the open heights, which gives you
a fully controllable Y axis. Imagine you have four
bends on a part. For the first few parts, you may
need the ram to come up only 1 in. between bends.
But for the final bend, you may need the ram to go
up 4 in. so you can remove the formed parts. With
a controllable Y axis, you can specify different open
heights in the program.
Remember the Humble Backgauge
To get the full benefit of CNC press brake opera-
tion, you may want to consider a system with a
full multiaxis system. Some now offer up to 8 axes
of gauging. However, the lion’s share of your pro-
ductivity savings may be achieved with a relatively
simple 2-axis (X and Y) system, either purchased
with a new press brake or retrofitted to an existing
machine. Well-used brakes can have backgauges
that may be in decent working condition, but have
an old, tired control. In this case, replacing only the
control, and keeping the existing backgauge, may
be an option.
Modern press brake controls have evolved to the
point where they show the operator the bend sequence graphically. Offline programming has proliferated as well, with modern CAD systems automating a lot of previously manual tasks. Software
now does the number crunching. And these days,
certain electric brakes can cycle up and down extremely quickly, which for some applications can
shorten bending cycle time significantly.
Setting up a complicated staged-bending arrangement is no longer such an arduous endeavor.
These complicated setups were possible on older
equipment, but actually performing them usually
was impractical. The runs had to be very long to
justify the prolonged setup time.
All of these improvements have helped productivity, for sure, especially when it comes to preventing errors from miscommunication, as well as prolonged setup and tryout times. These evolutionary
changes really have helped shops become much
more competitive. But when you think about
truly revolutionary productivity improvements in
bending over the past four decades, remember the
advances that happened back in the 1970s. That’s
when the humble automatic backgauge changed
Jim Ofria is president of Automec Inc., 82 Calvary
St., Waltham, MA 02453, 781-893-3403, www.au
tomec.com. Photo provided by Automec Inc.
allowed you to finish
all bends on the part