TPT July 2016

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JULY 2016 77
AR T I C L E
Advanced Machine & Engineering/AMSAW
Constraints for the machine designer –
the rules of saw design
When designing a machine, engineers must consider a series
of trade-offs. For example, a circular saw blade is torsionally
very stiff, but axially or laterally to the blade plane it is very
weak. The following equation describes this rule:
D = diameter
H = thickness
E = modulus of elasticity
k = factor which includes other constants and the
clamping ratio
Rule 1
As blades increase in diameter they can
cut larger stock sizes.
However…
Larger blades have larger vibration amplitudes
and larger blades are also more expensive to
purchase and maintain.
Rule 2
As blades get thicker they become stiffer
and vibrate less.
However…
Thicker blades are heavier and more expensive because
they cost more to produce, require more horsepower,
and are more difficult to maintain and re-sharpen.
Advanced Machine & Engineering | AMSAW – USA
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Rockford, IL 61103, USA
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How to reduce vibration in carbide sawing
If the machine does not follow the rules above, there’s not
much that can be done by the end user to reduce vibration.
Above all else, it’s critical for long term production results that
end users purchase a stiff machine with robust design.
Additionally, we have found that increasing the feed rate to
apply more force to the cut may actually help to stabilise the
blade in the cut.
Finally, it is important to understand the difference between
stabilising and damping, making sure that the machine is
equipped with the right components for both.
Vibration is the most harmful element in carbide sawing, but
other factors, such as resonance, and stabilising and damping
components must also be considered in machine design.
My next piece will highlight the damaging effect of resonance
and what can be done to prevent it, and my final piece
will distinguish between stabilising and damping, and how
machine designers utilise components to stabilise the blade
and control vibration to design machines with the lowest cost-
per-cut for the customer.
Figure 4: Vibration mode pattern of the second node diameters
typically occur at low rpm and have the most damaging effect