Designer Waveforms: Ultrasonic Technologies to Improve Cleaning and Eliminate Damage
(p. 12)
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Applying the Technology
Figure 11
The top image shows a multiple frequency system changing from 104 kHz to 40 kHz to 170 kHz to 40 kHz to 72 kHz to 104 kHz to 170 kHz with a non-constant sweep rate monotonically sweeping over a 4 kHz frequency range. Notice the shorter exposure times at lower frequencies to prevent cavitation damage.
The bottom image shows a constant power at every frequency with a degas time inserted between transitions from one frequency range to the next frequency range.
The improved part cleanliness is best demonstrated by graphs of percent particle removal versus particle size. It has been well established that higher frequencies remove a higher percentage of smaller particles. If this curve is assumed Gaussian in nature, then the graph shown in figure 12 results for a selected center frequency.
Figure 12
Particle removal for a selected center frequency.
The dotted line in figure 12 represents 100% and the reciprocal of particle size was used on the x-axis to spread out the small particle size numbers.
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