Vibration management is a key consideration in the design of any equipment. For high-magnification optic devices, it is critical to isolate the optic heads from external vibrations, such as typing on a workstation keyboard. Engineers at Design Continuum Inc., a product design and development firm, devised an inexpensive way to isolate the sensitive optics in a single molecule analyzer it developed for U.S. Genomics.
The goal? To develop a suspension system for the optic head with a natural frequency in the horizontal direction (the main mode of vibration for the analyzer chassis) of less than 1 Hz. Engineers initially considered a spring-based system, but Principal Engineer Mark West says the length of the spring required would have been excessive (see chart). Similarly, engineers could not achieve the desired frequency level with rubber bushings.
Engineers opted for a mechanical suspension system consisting of a parallel tie-rod pendulum that locates the center of mass at the point of straight-line motion. This economical alternative to air suspension is tuned to a natural frequency of 5.3 Hz in the vertical axis and less than 0.8 Hz in the horizontal axis. A pneumatically actuated pin locks the head in place when it is not in use.
Engineers tested the suspension system in their offices, which are near a commuter railway. Vibrations caused by trains rumbling by were not transmitted to the assembly.
CONTACT:Mark West, Design Continuum Inc. Tel: (617) 928-9536; e-mail: mwest@dcontinuum.comhttp://rbi.ims.ca/3855-500
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