Page 59 - June

PROFESSIONAL ADVICE

Vibration is a common issue

All sectors of industry recognize excessive vibration as a destructive condition. Repetitive
operating and/or external forces generate sympathetic motion that can resonate within a
machine, building, or bridge and grow to a dangerous magnitude. Manufacturers and builders
often apply tuned mass damper concepts to overcome vibration. A tuned mass damper is a
component that is suspended within a machine or structure and is designed to resonate out of
phase with the unwanted vibration, absorb its energy, and minimize the vibratory motion.
Vibration in metalcutting

In metalcutting, vibration is generated by the changing forces that occur when making
chips. The intermittent forces are apparent in the interrupted cutting process of milling and also
appear in turning operations when the toolholder bar is periodically loaded and unloaded as
chips form and break.
A passive approach to vibration control in
metalcutting involves maximizing the rigidity of
the elements of the machining system. To restrict
unwanted movement, a machine tool can be built with
rigid structural elements, made larger and heavier,
and filled with concrete or other vibration-absorbing
material. From a workpiece perspective, thin-
walled parts and those with unsupported sections
are prone to vibration when machined. To a limited
degree, parts can be redesigned to improve rigidity.
However, such design changes can add weight and
compromise product performance.
Fig. 1. Conventional tool: vibration propagates
along the machine spindle. For cutting tools, a passive approach to
vibration control includes use of short, rigid tools and
replacement of steel toolholders with those made of
stiff tungsten carbide.
A passive/dynamic approach to vibration
control for tools involves application of the tuned mass
damper concept. The Steadyline system from Seco
features a pre-tuned vibration damper consisting of
a damper mass made of high-density material (to
minimize its overall dimensions) suspended inside
the toolholder bar via radial absorbing elements. The
damper mass absorbs vibration immediately when it
is transmitted by the cutting tool to the body of the
Fig. 2. Tool for damping passive / dynamic vibration: bar.
the damper absorbs vibration before it propagates.

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