Process and parameters · 2 min read · Updated 2026-09-25
Particle size removal versus ultrasonic frequency
Lower frequencies make bigger, more energetic bubbles for heavy soil; higher frequencies make smaller, gentler bubbles that do better on fine particles. How to choose between 28 and 40 kHz.
Technical guide. Figures are taken from our own spec tables; for your process we confirm the settings with a cleaning trial.
There’s no denying that using ultrasonic cleaners is one of today’s top cleaning methods with its efficiency and eco-friendliness. The powerful ultrasonic frequency in these machines can effectively remove almost all types of debris and contamination on virtually any surface.
An ultrasonic cleaner removes contaminants of different particle sizes with the cavitation bubbles that the ultrasound induces in the liquid. These microscopic bubbles agitate the contaminants off from any surfaces like metals, plastic, rubber, glass, etc.
Ultrasonic cleaning also removes fine particles. Our industrial machines run at 28 kHz, 40 kHz or both, and at these frequencies they remove particles in the range of about 10 to 50 microns: fine sand, dust, swarf, silt and similar.
The rule of thumb in ultrasonic frequencies in these machines is that, the higher the frequency, the smaller the cavitation bubbles it induces. The agitation caused by the ultrasonic frequency implodes these microscopic bubbles which results in the cleaning action.
Having your ultrasonic at a higher frequency is optimum for parts with finer contaminating particles. It also results to gentler cleaning on these parts. On the flipside, a lower ultrasonic frequency in your machine produces relatively larger cavitation bubbles which are perfect for cleaning parts which have bigger contaminating particles.
However, in reality, there are instances that the contamination of the parts you need to clean are a combination of these small contaminating particles with grease, oil, dirt and/or wax and pigments. You have to take this into consideration when choosing the ultrasonic frequency of your ultrasonic cleaner.
A turbocharger that comes in for overhaul is a typical example: carbon deposits and fine swarf, held to the surface by oil residue. The particles are small, but the oil binds them, so the job needs strong cavitation together with a heated cleaner that breaks down the oil. That points to the lower frequency, 28 kHz.
At Sonixtek you choose the frequency of your industrial ultrasonic cleaner: on the ST Industrial Standard Series you choose 28 kHz or 40 kHz when ordering, and the UMX Pro is available with single or dual frequency. Sonixtek ultrasonic cleaners from the industrial up to our advanced series suit a wide range of products which includes automotive, aircraft, hardware, and plumbing materials.
