Over the years press brake machines
have undergone three big changes: how the machines are driven, how they
are automated, and, finally, how parts flow through them.
Rapid advances in sheet metal
fabricating technologies can produce amazing results. The latest “big
thing” to hit the industry is the fiber laser. The productivity gain
from these machines is spectacular—well, until you find a mountain of
flat blanks in front of your press brake.
Over the years press brake machines have undergone three big changes:
how the machines are driven, how they are automated, and, finally, how
parts flow through them (see Figure 1). The challenge
most fabricators face is understanding these transformations and how to
apply them to their situation. Applied correctly, though, they all work
together to free the bending bottleneck.
During the first half of the 20th century, most press brake ram drive
systems had a motor, flywheel, eccentric crank, and brake (hence the
name press brake). The flywheel stored a massive amount of kinetic
energy, and the clutch engaged the bend cycle. The eccentric crank
transformed the rotary motion from the flywheel to the linear pressing
motion of the ram. The brake halted the bend cycle.
To address this, fabricators willingly
sacrificed SPM on their press brakes for flexibility. This change
affected the heart of the press brake, with a complete redesign of the
press drive itself. These newfangled hydraulic press drives, with their
associated flow control valves, offered total flexibility of ram speeds,
stroke lengths, applied force, and, most important, variable bend angle
These first-generation hydraulic press drives were not as dynamic as
the mature mechanical press drives were. To compensate for this
“sponginess,” press brake manufacturers simply slowed the ram speeds.
These flexible press drives dominated the sheet metal industry until
recently, when demand shifted once again from JIT manufacturing to mass
customization. This revived need for speed provoked press brake
manufacturers to reassess the main press drive once again.
The obvious choice was to replace hydraulic fluid with a modernized
mechanical system. This led to the birth of the electric press drive.
The term electric press brake is now commonly used to describe a
direct press drive system, from the torque of the motor to the linear
pressing motion of the ram.
This sounds simple, but there is a huge gear reduction needed to
transform thousands of RPMs at the motor to tens of inches per minute of
pressing motion at the ram. The simplest way to achieve this reduction
is to use an inclined plane wrapped helically around a common axis (also
known as a screw).
A popular alternative to the screw drive is a system of pulleys with
belts threaded in between, like a block-and-tackle pulley for lifting
heavy loads (see Figure 2). This drive distributes the loads over various components.
Although these electrical press drives
can achieve high speeds, there is a mechanical limit between the highest
and lowest possible speed. In operation, though, press brakes use a
wide range of ram speeds. Rapid approach speeds need to be as high as
700 inches per minute (IPM), while bending speeds need to be as low as 5
IPM. For conventional hydraulics, going as slow as 5 IPM and as high as
700 IPM isn’t a problem.
Another upcoming drive type is the hybrid hydraulic-electric press
brake. As the name suggests, these press brakes use both hydraulic and
electric systems. Hydraulic pressure drives the press brake ram, but the
direction of AC servomotors determines the direction of the ram
movement. Hydraulic fluid isn’t constantly on the move as it is with
conventional hydraulics, so some efficiencies are gained.
In hybrid press brakes, fluid flows only when the operator depresses the foot pedal. Ram precision is quite high. The most notable feature of these systems is that the classic directional valves and their associated shifting times are eliminated. In a hydraulic press brake, the valve-shift time is most notable when the ram transitions from a high-speed approach to low-speed bending, and again between low-speed bending to the high-speed return stroke. In a hybrid press drive, when the pump speed or direction changes, the ram’s speed and direction do the same immediately thereafter, no shifting time required.
In the sheet metal industry, huge
changes in technology are coming with a whole new way of thinking about
production efficiency. This involves Industry 4.0, or the fourth
Industrial Revolution. The first Industrial Revolution came with water
and steam power; the second came with mass production with the help of
electric power; the third came with electronics and the use of
Industry 4.0 is a term for a connected production environment where
each part of the whole value chain talks to and with each other, sharing
information via a network to improve the entire process. With this
game-changer, fabricators can finish more orders in less time than ever
before. The aim is for every stage of production, including the planning
stage, to have the correct information at the right time. “Trial
balloons” or “test shots” are no longer necessary.
Industry 4.0 has had profound effects in the press brake department.
No longer do operators spend time programming, test bending, inspecting,
and adjusting. Technicians create and simulate the bend program
offline. The machines measure and correct for angular error. All this
allows for a greater number of small-volume jobs to flow through the
press brake in less time (see Figure 3).
Nevertheless, press brake technicians today must deal with a counterintuitive reality: The newer the press brake, the higher
the percentage of tool-changing time will be. Here, we’re defining
“tool-changing time” as a portion of overall setup time, which
historically has also included programming, tryout, measuring, and
Modern press brakes have massive part program storage capacities, so
all programs can be saved; artificial intelligence databases correct new
programs; and automatic stabilization systems compensate for material
variations. New brakes are set up with a swipe of your finger across the
screen—except for the tooling. In many cases, tooling changeout exceeds
80 percent of the total setup time.
Automatic press brake tool changers seize this opportunity.
Robotic press brakes usually are dedicated to a small group of parts,
and they usually reduce the number of part configurations you can have.
Tool-change automation, on the other hand, does not compromise the
basic machine design or the number of part configurations the press
brake can bend.
Automatic tool changers can retrieve, remove, rearrange, and rotate tools when a job requires them to be installed backward (see Figure 4). Think of a gooseneck punch that needs to be reversed so that it can clear a preformed extrusion on the blank surface. Such a setup can confuse even veteran operators.
Almost every manufacturing process has
many linked activities, one of which acts as a constraint—the weakest
link in the chain. Because of all the different part configurations
sheet metal fabricators deal with, constraints can be elusive; they tend
to bounce around from one process to another.
Fab shops bend parts ranging from the size of a postage stamp with a
single bend to parts the size of a car with 10 bends; between these
extremes may be tens or hundreds of incremental variations. Shops also
deal with varying batch sizes, from one piece to hundreds.
Each product may take a unique path, so the constraint patterns can
be hard to identify. Look for accumulations of work-in-process, a
telltale sign that occurs just before the constraint. Also look for a
concentration of workers; constraints tend to attract additional human
resources. Review equipment performance to better understand its overall
equipment effectiveness. Most important, ask operators about
bottlenecks they experience.
Most fabricators organize their shops in process-based departments.
But nearly all parts are cut with a punch or laser, and most parts
undergo bending—so why not create a cell at the laser? An operator could
pull the blanks from the nest, bend them, and then place them in the
transport bin for the final process.
Part flow usually isn’t this simple, unfortunately. Every part isn’t processed in the same way. Putting the press brake too close to the laser would actually block production of large parts. The cost of temporarily moving a press brake for one job would exceed the cost of moving the parts. So keeping the press brake in its own department is again accepted as the cost of doing business—until recently, that is.
There is a reason most press brakes on the market have between 150
and 320 tons of forming force. This is the “sweet spot” for press brake
work, where you get the most tons per dollar. The size is also
convenient for press brake builders because several assembly crews can
build one machine simultaneously. Press brake builders can take
advantage of scale here, too, because the market demand for bending
0.25-in.-thick material, or somewhere around 16 tons per foot, is quite
The boom in Silicon Valley, though, created significant demand for a
different press brake. Floor space was expensive; computer chassis parts
were very small. For these applications, the high force and long bed
length of the 150- to 320-ton machines had no value. Their cumbersome
size actually reduced versatility. Ultimately, this market was willing
to bear doubling the cost of the tons per dollar to buy a conveniently
sized press brake.
Today installing these small machines doesn’t require a special
foundation. Moreover, training isn’t arduous, considering how intuitive
modern press brake controls are.
Most recently small, portable press brakes—many either all-electric
or hybrid hydraulic-electric machines—have become more popular, not just
for the forming speed they offer, but also because of their
flexibility. Their low centers of gravity make them portable, and
integrated fork truck slots reduce the tip-over risk even further.
Now you can move your press brake production to where you need it, when you need it, and back again. Certain machines can go from running production in one location to running production in another location in less than 5 minutes (see Figure 5).
Fabricators now have new press brake
drive systems, including hydraulic, electric, and hybrid
hydraulic-electric. They have the benefits of automation, including not
just physical automation (think robotic bending and tool changing), but
also the sensors and software that process intelligent data. And finally
they have part flow flexibility, the ability to move bending machines
when and where they’re needed.
Imagine you have two cells. In each you’ve implemented basic 5S:
sort, set in order, shine, standardize, sustain. Tools are kept close in
rolling racks adjacent to the press brakes (see Figure 1).
One cell has a high-speed fiber laser feeding several press brakes
and a hardware insertion machine. Designed for a different product mix,
another cell has two punch presses, a laser, one highly efficient press
brake with automatic tool changing, and an adjacent small brake to
Now imagine that demand levels change and the first cell needs
additional forming capacity. A fork truck driver moves the small press
brake from the second cell to the first. The technician downloads the
programs, and the brake, which carries its tools in drawers inside the
machine base, is set up quickly. Soon the cell has the extra bending
capacity it needs to keep the flow going.
Flexible manufacturing is not guaranteed just by having a small press
brake in your shop. It’s how you balance the loads and direct the parts
to best take advantage of the machine’s inherent sweet spots.
That said, we’ve come a long way from the old mechanical press brake. And it couldn’t happen without modern drive systems, controls, and software—all working together to ensure every machine (and operator) has the information it needs at the right time. Industry 4.0, it seems, has arrived.
As published by The Fabricator, June 2016.
Marcel Fiedler , Applications Engineer, Bystronic Inc.
Paul LeTang, Press Brake Product Manager, Bystronic Inc.