up against the band saw machine’s guides; these tapers cause the blade to oscillate slightly up and down. ;is in turn causes the blade to enter the workpiece in a rocking motion, causing the blade to cut on multiple planes. ;e
result: Fewer teeth engage the metal at once.
;is means that it takes less cutting pressure per inch to remove metal,
which produces a smooth cut surface. It also improves cutting e;ciency and
shortens cycle time.
2. What are my overall cycle times?
;e actual cutting is just one component of the overall cycle time. After cutting, the saw lifts out of the cut, indexes the material, clamps it, and descends
the blade to begin the next cut. In recent years machine manufacturers have
worked to significantly shorten indexing time, and for good reason. With the
actual cut time dropping, all the other elements of a band sawing cycle, including indexing time, become much more significant (see Figure 2).
Similarly, material handling processes have helped automate loading and unloading. Some modern band saw systems have sophisticated magazines that
you can load, and programs can be made ahead of time and loaded into the
CNC, eliminating programming time during the changeover. O;oading systems have advanced as well. Taken all together, a band saw system now can
operate lights-out, unattended—something that not long ago just wasn’t feasible.
A comprehensive understanding of work flow needs to enter the equation
too. After o;oading, cut material needs to flow e;ciently to downstream processes. Productivity gains are harder to come by if you’re just overloading a
downstream operation. If you do this, your band saw may be twice as e;cient,
but you may not be shipping any more products than you did before. For this
reason, be sure to keep the entire work flow requirements in mind.
3. How much scrap and rework
do I have?
Band saw scrap and rework drive costs up and hamper productivity. Most
blade and machine manufacturers have recommended speed and feed charts.
Besides characteristics of the blade itself, two primary factors regulate how
quickly a saw makes a cut: One is the rate of descent of the sawing head, and
the other is the pressure associated with that descent. Many view these as one
and the same, but they are not.
Some operators let the rate of descent exceed the blade’s beam strength or
ability for the teeth to penetrate. ;is puts excessive pressure on the teeth and
causes the teeth to strip or the band to bend. From there the band takes the
path of least resistance, deflects left or right slightly, and begins cutting down
;is band saw indexes quickly to bundle-cut rectangular tube. With the actual cut time
dropping, all the other elements of a band sawing cycle, including indexing time, become much more important.
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at an angle, causing a crooked cut. Crooked cutting also can be caused by too
fine of a tooth pitch for the work being sawed, low blade tension, or worn
A poor or crooked cut may need to be recut, trimmed, filled with weld, or
scrapped entirely. For aerospace material in which component weight is critical,
the tolerance is zero for crooked cutting, and the cost of that rework and scrap
adds up quickly.
In this case, reducing the feed can overcome the problem. Alternatively, a
tapered back blade can help, because fewer teeth are simultaneously engaged
in the cut. With fewer teeth engaged, you get better penetration and reduce the
risk of deflection.
Be aware also that you shouldn’t feed too lightly, either, because that will
cause another problem that can lead to premature blade wear and a rough cut
finish: premature tooth dulling from rubbing, not cutting. Dulling teeth take
the path of least resistance, which often is to either side, and not straight down.
Band saws now slice through metal
at an unprecedented rate.