VST offers Mechanical Shakers in 3 basic configurations, single shaft (Elliptical), two shaft (Vertical), and four shaft (Vertical & Horizontal).Table sizes range from 30" x 30" up 120" x 120" and beyond with payload capacities up to 20,000 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 creating an unbalanced shaft. The CG offset creates a Reaction Moment equal to the mass of the weights x the CG's distance from the shaft center line (center of rotation). Reaction Moment Shakers produce sinusoidal motion and have a fixed displacement. As RPM or Frequency varies, the displacement or total distance the table moves stays constant while acceleration changes directly with Frequency. Mechanical Shakers have a an effective frequency range from ~5-60 Hz.
The lowest frequency is determined the natural frequency of the suspension system, as the frequency of vibration approaches the natural frequency of the suspension system there will be an increase in displacement. The Shaker system can go down to 5 Hz but it's displacement will not be constant at varying lower frequencies.
Mechanical Shakers are generally limited to 10 g's to prevent motor failure. 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, Mechanical 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 (VFD) and utilize air springs 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. Shakers used with Environmental Chambers can be supplied with a thermally insulated top and diaphragm support arms.
ES 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 grow crystals.
VS series Vertical Shakers utilize 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.
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 moving mass.
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 center lines. 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 center lines. 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 cosine of the Phase Lock Angle.
UL 203, ASTM, ACI, ICC-ES, City of Los Angeles, California, Miami-Dade BCCO, ICC-ES AC193, ICC-ES AC308, ACI 355.2, and ASTM E488, as well as ICC-ES AC01, ICC-ES AC58, ICC-ES AC70, ICC-ES AC106, ASTM E1512
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