VST offers Mechanical
Shakers in 3
basic configurations, single shaft (Elliptical), two shaft (Vertical),
and four shaft (Vertical & Horizontal).
Table sizes range from 18" X 18" up 120" X 120" and beyond with payload
capacities up to 15,000 lbs. and higher.
Mechanical Shakers can be used for
design qualifications, end product reliability and fatigue testing,
environmental stress screening (ESS), as part of a production process
such as quality assurance, or anything else that requires vibration.
Mechanical Shakers generate
vibratory forces by rotating
eccentric masses (masses with an offset Center of Gravity), essentially
shaft. The CG offset creates a Reaction Moment equal to the mass of
the weights x the CG's distance from the shaft centerline (center of
Reaction Moment Shakers produce sinusoidal motion and have a
fixed displacement. As RPM or Frequency varies, the displacement or
distance the table moves stays constant while
acceleration changes directly with
Frequency. Mechanical Shakers have a an effective frequency range from
~10-60Hz. The lowest frequency is determined the natural frequency of
the suspesion system, as the frequency of vibration approaches the
natural frequency of the suspension system there will be an
displacement. The Shaker system can go down to 5Hz but it's
displacent will not be constant at varying lower frequencies.
Mechanical Shakers are generally limited to 10 g's to prevent
However, in special cases the motor can be mounted on the base frame to
increase the 10 g limit. While
seemingly limited compared to an Electro-Dynamic
Shaker, Mechnical Shakers
are capable of producing very high forces at a fraction of the cost.
All VST Mechanical Shakers are controlled with a Variable Frequency
Drive and utilize airsprings to isolate the moving mass from the base
frame. VST's Vibration Tool software interfaces with the VFD allowing
for frequency sweeping and timed profiles as well as vibration
monitoring. They can be supplied with regular
locking casters and or
V-Groove casters and tracks for use with Environmental Chambers.
used with Evironmental Chambers can be supplied with a thermally
top and diaphram support arms.
series Elliptical Shakers are the lowest cost series and utilize a
single shaft to create motion in both vertical and horizontal axes
simultaneously. They are typically used for
applications which require more than a single direction vibration. The
ES shaker is an inexpensive solution for production line
Environmental Stress Screening (ESS). An alternate version of this
shaker where the elliptical motion is induced in the horizontal plane
(shaft mounted vertically) has been used by Pharmaceutical Companies to
VS series Vertical
two counter-rotating shafts to create motion in the Vertical Axis only.
The two shafts are timed together but rotating in opposite directions.
Horizontal forces generated by the shafts get canceled out and result
in the forces being applied
in only the Vertical Axis.
Vertical & Horizontal Shakers
VH series Vertical &
Horizontal Shakers utilize four shafts to create motion in either the
Vertical or Horizontal Axes. The shaft configuration is basically two
VS series put together, one on each end of the shaker. Each end has a
set of counter-rotating shafts that are timed to each other like the VS
series shakers and each end is timed to the other. The VH series
shakers have an adjusting mechanism to allow the
timing to be changed for Vertical or Horizontal mode and to allow the
Phase Lock be set in Horizontal mode.
Vertical mode is
pretty straight forward. The eccentric masses are timed in such a way
so they act like two VS series shakers running in unison. Horizontal
forces cancel each other out while the vertical forces act on the
Horizontal mode is a little more
complicated as there needs to be a way of compensating for the CG which
will be located above the shaft centerlines. Each counter-rotating
shaft set is timed so the force vectors are inline when the eccentric
masses are horizontal and opposing each other when vertical. Each
counter rotating shaft set is timed to the other so that all the force
vectors are in line with each other when they are horizontal thus
applying force laterally and they cancel each other out when vertical.
The Phase Lock setting is the key to making this work so the there is
no rocking motion induced due to the CG being above the shaft
centerlines. The Phase Lock Angle changes the timing slightly to
aim the horizontal force vector at the CG of the system. The amount of
applied force for a given Reaction Moment is reduced by the cosθ
of the Phase Lock Angle.