Before understanding the frequency difference between 28kHz and 40kHz ultrasonic cleaners, let's understand firstly what the two parameters mean: 

28kHz means 28,000 vibrations per minute; 40kHz means 40,000 vibrations per minute.

Frequency is a major factor while choosing an ultrasonic cleaner. It also determines the cleaning strength. 

When the ultrasonic frequency is low, the wavelength is large, and the generated cavitation bubbles are big. 

The impact force on the workpiece surface is large. Due to the large wavelength, the sound field distribution in the cleaning tank is not so even. 

So the lower frequency ultrasonic cleaner is suitable for cleaning workpieces with heavy dirt or difficult to clean.

Generally speaking, 28kHz ultrasonic cleaner are used in cleaning hardware, machinery, automobile and motorcycle, aerospace, train, ship, mining,

automotive, compressor and other industries. 

When the ultrasonic frequency is high, the wavelength is short, the cavitation bubbles produced are small, and the intensity is low, 

The impact force on the surface of the workpiece is less powerful. Due to the small wavelength, the cavitation bubbles are fine.

Because the sound field distribution is more uniform, and the penetration of the sound wave is enhanced, 

and the ability to disperse and emulsify small dirt is also enhanced. 

Therefore, higher frequency ultrasonic cleaners are suitable for precision cleaning, high surface precision and complex shapes.

40kHz ultrasonic cleaner is mostly used for optical and photoelectronic cleaning and circuit board cleaning.