Band Sawing Technology
Article By Doug Harris
Vice President, HE&M Inc.
The strong economy of the
1990’s challenged saw builders to produce more capable
machines with better reliability at a competitive price.
Today’s saw manufacturers have responded with
innovations like double-column saws that provide a heavier and
more rigid cutting platform, bar feeds with sophisticated top
clamping, bi-directional vising that allows easier cutting of
mill bundles, and more stringent requirements for length
Customers want fully
hydraulics saws with full-stroking vises, hydraulically
powered guide arms, sensors that display blade deviation,
digital band speed readouts, digital feed rate displays, and
pushbutton blade-speed settings.
A recent innovation is the double-column band saw with
an angled blade entry (cant) that reduces blade pinching,
allows a more uniform chip, and increases blade life by
reducing total band load. A 1.5° tilt to the blade entry angle was an immediate
success among users. The
increase in the speed of cutting structurals and bundles was
dramatic, and significantly boosts production while reducing
cost per cut.
industry drove development of band saws with a 9° blade entry
angle to cut large wide-flange beams.
Internal stresses, created during the manufacture of
wide flange, can cause pinching as the cut relieves residual
developed for wide-flange material, the 9° cant and wide-set
blades nearly eliminate the pinching problem.
Canted blades also
reduce the total number of teeth in the cut, which allows
blades to be used to their fullest capability.
In the past, older horizontal and vertical-blade band
saws often had either too many or too few teeth in the cut, so
blade teeth were often stripped or broken.
Blades never got dull; they were destroyed.
Today’s 9° blade cant allows blades to wear out
gradually over the course of a long, useful life.
Feed Systems have made quantum leaps from the old positive
stop 24” (610-mm) feed, to today’s 144” (3.7-m) bar
systems are positioned by computers to tighter tolerances than
ever before. When a shorter far feed is used, tolerance build-up occurs
because multiple strokes are required to feed stock. Longer bar feeds that use continuous feedback systems can
drastically improve length consistency and speed of index for
Remnant lengths were
also drastically reduced from perhaps 24” in the 1970’s to
as little as 3” (76-mm) today by split vising and
interlocking vising techniques.
Load capacities have also increased.
Mill bundles weighting more than 12,000 lbs (5450 kg)
are common on today’s larger band saw systems.
Improved blade and
band saw technology place high demands on total accuracy,
since the output from a band saw often goes directly to a
robotic welding machine, which will have no tolerance at all
for out-of-tolerance parts.
Newer, faster, computer-driven bar feeds with special
sensors and rive systems are more reliable, smoother, and more
accurate than ever before.
manufacturers in industries as diverse as rapid transit,
agricultural equipment, rail, aircraft, and commercial trailer
forced the development of the 144” digital bar feed designed
to hold exceedingly tight tolerances.
These new feed, equipped with bi-directional vises and
improved top clamps, combine with double-column, 9° cant
blade band saws with capacities reaching 25” (635-mm)
vertical by 50” (1.3-m) horizontal to create
high-performance sawing packages.
Some systems have
powered lifting rollers to speed material to and from the saw.
To improve productivity, many companies are purchasing
material handling systems that include side loading and
hard-to-cut aerospace materials such as Hastelloy, titanium,
and Inconel, saws had to become heavier and bigger.
Larger-diameter band wheels were necessary to put less
stress on the blade. Guide arms and saw arms became heavier and larger to dampen
vibration and withstand blade tensions as high as 50,000 psi
(345 Mpa). In
addition, larger gearboxes were necessary to run these larger
carbide-tipped band saw blades needed to cut these materials
are very unforgiving, computer control systems have to
maintain positive command of the cutting operation.
When cutting work-hardening materials such as Inconel,
it’s necessary to maintain constant chip load.
Today’s computer-controlled traverse systems provide
the cutting control that makes using carbide blades, even when
cutting exotic materials, much more efficient and
Since the carbide
blade is more heat-resistant than mi-metal and can withstand
much higher feed pressures than a tool-steel blade, band speed
can be much higher. More durable than bi-metal, a carbide blade retains its
sharpness longer than a steel blade, and produces a better
surface finish than cutting with bi-metal.
This improved finish allows cut-to-length tolerances to
be held even tighter to reduce or eliminate downstream
Carbide is good in
compression but not in tension, so a carbide blade requires a
soft exit from the cut to prevent damage.
The band saw controller automatically reduces force and
rate near the very end of a cut to prevent the blade from
exploding out of the cut, which would cause tooth damage.
Carbide band saws
are still a new technology.
Specially designed carbide band saws will revolutionize
the saw industry just as carbide inserts revolutionized the
machine tool industry in the 1980’s.
and more efficient cutting provides yet another challenge for
the band saw manufacturer: how to get material to the saw and how to remove it.
In times past, the saw was a manufacturing bottleneck.
In the coming decade, manufacturers and steel service
centers will want to move material to the saw and away from
the saw as quickly as possible.
Instead of a forklift or overhead crane waiting on a
saw to finish a job, the saw will probably be waiting for
someone to unload it.
loading and unloading tables may speed stock to the band saw,
and move the saw’s output to the next manufacturing step.
Scrap will be automatically dumped into special bins,
sorted for length, and placed into containers for later use.
Saw operators will be able to automatically determine
the optimum use of bar stock, based on data entered at a
computer-controlled traverse systems already provide a smooth
and predictable blade break-in process.
After installing a new blade, the saw operator simply
pushes a button on the console, and the computer automatically
adjusts cutting forces to properly break in a new blade,
substantially improving blade life.
Saw computers will
soon be communicating with warehouse inventory computers to
determine which jobs run first, second, or third.
Ultimately, a bar code on material will contain
information such as material type, hardness, traceability,
source, final destination, and other information including
quantity and length required.
The saw will automatically adjust itself to the proper
feeds and speeds, lengths and quantity, and the material
handling system will deliver the cut-to-length parts to the
will be able to plug their laptops or cellular telephones into
a band saw’s computer to download information such as the
saw’s service history, the number of cycles it has made, the
number of hours the machines has been operated, and any
glitches or faults the computer may have recorded.
Band saws can now be placed online, and diagnostics can
be transmitted through the Internet.
In just a few
decades the band saw has changed from a back-shop necessity to
a double-column saw with an 80 x 80” (2 x 2-m) capacity and
a 4” (100-mm) blade. Today
only one thing is certain; somebody is still going to have to
change the blade from time to time – and even that task may
be automated in the not too distant future.