part collides with tooling and gauging as it’s being
formed, or the tooling needed to form the part isn’t
available, or the blank dimensions are incorrect.
To fix the problem, the operator may go back and
forth with engineering, or he may just try to “make
it work” with the tooling he has. This can lead to
problems downstream and create an undocumented process, which can make training and process
standardization even more difficult. Just “making it
work” is never ideal.
Offline bend programming is becoming more
and more common. In the not-too-distant future,
it’s likely to become standard, particularly in high-product-mix situations. For this reason, the time
study in Figure 1 does not incorporate programming
at the machine.
It also assumes that the operator is working with
a modern press brake controller—hence, it takes a
minute (or less) to read the print and verify the program is correct. The control provides the operator
with a 3-D visualization of the process, so the operator need not spend a lot of time studying the drawing and work instructions to determine the bend
The time study does, however, incorporate
altering the program as an element of the “part run-in.”
This time mainly involves first-article quality checks
and adjustments the operator makes because of
material variation, particularly in material thickness. The operator measures the thickness of the
cut blanks in front of him, then enters that new material thickness into the control, which (at least ideally) makes the appropriate adjustments. After that
the operator bends another test part and measures
it with a caliper and protractor. And he may have to
take the part to the quality department, if the job requires it. All this can eat up time, which is why “part
run-in,” or part tryout, consumes such a large portion of the time study.
It’s also where fabricators can eliminate significant inefficiencies. It’s always ideal to “engineer
out” a problem, and with prolonged part run-ins,
this sometimes can involve scrutinizing the material and how it’s presented to the press brake operator. The more consistent material quality is, the less
time an operator will need to spend tweaking setups to accommodate for material variation.
Cutting strategies play a role here too. Depending
on the material and job requirements, a change in
grain direction (that is, bending with or against the
grain) may require a bending adjustment, which
takes time and adds variability to an already complex bending process. When practical, the nesting
programmer should try to keep the grain direction
on identical parts uniform.
Shortening the part run-in also can involve some
low-hanging fruit. What if an operator spends time
searching for calipers and protractors or must walk
across the floor to retrieve those measurement
tools? Here a fabricator can implement some basic
5S, such as placing tools on shadow boards, to ensure every press brake has the properly calibrated
tools necessary for the operator to complete his job.
An operator also needs something to write with to
record measurements on the job packet.
Recording those measurements on test parts
tends to be a manual job. In between a laptop or
computer terminal where the operator clocks in and
out of the job and an advanced CNC on the press
brake itself, an operator still puts pencil to paper to
record measurements during part run-in and for periodic quality checks.
To eliminate this task, automation and digital
technologies have played key roles. Some operations now use digital measuring devices that connect directly to the CNC. An operator runs a test
part; measures it; and the resulting data feeds directly into the control, which then has the information it needs to make the appropriate adjustments.
This still involves forming a test part and manually
measuring it, of course. To streamline operations
further, a fabricator can invest in automatic bend
angle correction (see Figure 2). These technologies come in various forms, incorporated into the
press brake and tooling, but they all aim to measure
the bend angle in-process and make corrections.
The desired result: The first test piece should be a
The remaining piece of the bending process puzzle
involves the actual tool change. Low-hanging fruit
here includes basic tool organization and ensuring
Automatic angle measurement and correction can help minimize part run-in time. A tactile measurement system is shown on the left, and a laser-based measurement system
is shown on the right.
This automatic tool changer can be added to certain manual press brake models. A conveying system pushes and
pulls tools into designated slots.