June 15th. 2007
MECHANICS 2.0: ULTRASONIC CLEANING
Acoustic (sound) waves are compression waves consisting of alternate series of condensations and rarefactions (expansions). Meaning, the particles of the sustaining medium; a fluid, vibrate parallel (along the axis) to wave propagation. The vibration is due to a disturbance. The disturbance advances, not the medium; waves transport energy, momentum, and in some cases, information. An equally valid description of an acoustic wave is a pressure wave. Relatively higher than atmospheric pressure corresponding to the condensation and lower than atmospheric pressure corresponding to the rarefaction.
Frequency is the number of complete wave cycles that pass a reference point per second. This unit of cycles/second is called a hertz; Hz. The human ear can detect frequencies between 20 and 20,000 Hz. For most of us frequencies below 20 Hz are referred to as infrasonic and those above 20,000 Hz are ultrasonic.
Ultrasonic Cleaner: Ultrasonic Cleaner
Ultrasonic waves in an appropriate cleaning solution causes the formation of minute bubbles; technically, vacuum cavities. These vacuum cavities form during the low pressure phase. During the following high pressure phase the bubbles implode with tremendous force (on the microscopic scale). Alternate bubble formation and implosion is the caviation process. The implosive force is very consistent and provides an intense cleaning action that "pulls" contaminates from surfaces. Several plus factors of ultrasonic cleaning: the bubbles are small enough to pentrate microscopic openings; dissembly of intricate parts is therefore reduced or not required; most ultrasonic solutions and rinses will not harm seals, gaskets, and bearings. However, unlike bead blasting, ultrasonic cleaning will not return showroom luster to antique metal but it does eliminate the hours of rinsing needed to rid the part of disastrous glass. Heavy sludge and grit must be removed prior to ultrasonic cleaning. Ultrasonic cleaners are also expensive, ranging from $2,000 bench-top models to $15,000 or more for floor models. My current unit (tank size 11.5X9.5X6") is capable of operating with a sweep frequency between 38,500 Hz and 40,500 Hz with solution temperatures up to 80 degrees Celsius (176 degees Fahrenheit). I have found this combination excellent for carburetors, /2 heads and barrels and Harley oil pumps.