can be beneficial, especially one with
quick-change capabilities.
Safety. As always, safety must be a
very high priority. The rated capacity
of the punch and die always should be
checked against the amount of force
that will be applied during the bending process.
It is also important to remember
that a tool with a rated capacity of, say,
12 tons per foot does not mean that
you can apply a total of 12 tons of
force over any length, regardless of
how long or how short the part length
or the tooling is. It means that a tool
with a rated capacity of 12 tons per ft.
is capable of handling a maximum of 1
ton per inch of bending force.
Subsequently, if you were to apply 12
tons of bending force over 6-in.-long
tooling that is rated at 12 tons per ft.,
you would be using the tooling at
twice its rated capacity. In like manner, a tool with a rated capacity of 24
tons per ft. is rated at 2 tons per in.
Finally, it is always a good idea to
use punches with safety clicks or safety tangs, especially with large, heavy
punches. This helps reduce the risk of
operator injury and damage to the
tooling during loading and unloading.
Clamping. As mentioned previously, handling large, heavy tooling is
one of the greatest contributors to the
cost of bending. One of the best ways
to reduce setup time is to install a
quick-clamping system on the ram of
the machine.
This system enables the operator to
clamp the punches without the use of
cumbersome wrenches and levers.
Some of the hydraulic versions also
have the ability to clamp, seat, center,
and align the tooling with the push of
a single button.
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CFIGURE 2 This large-radius punch and punch holder with a quick-change,
adjustable die is equipped with rollers on the shoulders that significantly reduce
bending force requirements to bend thick material.
These new breeds bring with them
the need for new tools and new rules
for proper bending.
Crowning Systems Counter
Deflection. The higher amount of
bending force required to bend HSS
will increase machine deflection. It will
also increase the need to compensate
for deflection when bending parts that
require good accuracy and parts that
are typically 8 ft. long or longer. Using
the old method of shimming dies is
rarely acceptable as it is very time-consuming. Shimming also damages the
die holder because the force is partially
concentrated over the shims instead of
being dissipated over the full load-bear-ing surface of the lower die holder. This
will create the need to have the lower
die holder machined periodically, thus
adding cost to the overall operation.
The best solution for attacking the
problem of machine deflection is to
install a crowning system on the bed
of the machine. Today’s crowning sys-
tems come with a host of features that
are designed to allow you to tailor
them to your specific needs and budget. Features include opposing waves to
improve accuracy; localized adjustments to allow the operator to compensate for local wear in the ram and
bed of the machine and/or the tooling; drive motors that are interfaced
with the control; lower-cost, manual
handcranks for the adjustment of the
crown; hydraulic die clamping for
rapid die changes; and manual clamping in the form of clamping bars that
allow for the use of sectionalized tooling or set screws to provide an inexpensive method of securing long,
planer-made dies. ■
David Bishop is business development manager, Wila USA, 9135 Guilford Road,
Columbia, MD 21046, 301-490-9652,
dbishop@wilausa.com, www.wilausa.com.
Want more information?
Visit www.thefabricator.com; enter the article number (digits only) in the
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• “Introduction to advanced high-strength steels” 1139, 1158 ( 2 parts)
• “Air forming and V-die selection” 895
• “Safety still pressing for press brakes” 1525
The FABRICATOR | An FMA Publication
www.thefabricator.com | March 2007