Ultrasonic cleaners utilize a transducer attached to the tank’s exterior. The transducer
outputs pulsating mechanical energy at high frequencies (ultrasonic), which cause the
liquid in the tank to agitate.
The agitation at this high frequency level is what gives ultrasonic cleaners their cleaning
ability. As the liquid becomes agitated, a phenomenon known as cavitation takes place.
Cavitation is the almost instantaneous formation and implosion of small bubbles and
cavities in the cleaning liquid.
As the liquid cavitates, the minute bubbles and the coincident implosions cause the
surrounding liquid to impinge forcefully upon the surface areas of the part being cleaned.
The force that the liquid applies to the area of the part is commonly referred to as the
scrub-force.
This scrub-force action takes place throughout the tank. However, the scrub-force can
vary significantly due to the placement of the tank’s transducer and the constructive and
destructive interference caused by the shape of the tank and parts being cleaned.
These process variations in scrub-force throughout the tank can be referred to as hot or
cold spots in the liquid. Hot and cold spots are locations of high and low intensity scrub-
force relative to a mean value scrub-force. These process variations can significantly
alter the cleanliness or integrity of the parts being cleaned. Some parts may not have
been thoroughly cleaned for the next process, or the stresses due to the cleaning action
may have altered the integrity of the parts. With the Sonic Meter these process variation
can be minimized.
With the Sonic Meter’s slender probe, operators can probe ultrasonic cleaners to
pinpoint areas of optimum intensity in which to place each part. The Sonic Meter’s
displays the intensity variations. Parts could be varied in their z-height or their x and y
positions via an adjustable array fixture. The operator can determine the location for
each part so that all parts are placed in regions of the same specified pressure range
(scrub-force). Or several readings could be taken and averaged to determine the mean
value scrub-force of a particular cleaner.
The Sonic Meter
SM1000
measures scrub-force in units of pounds per square inch
(psi). The
SM1000
works with tanks that use frequencies in the range of 0-500kHz.
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