Ultrasound through magnetostriction vs. piezoelectricity

Ultrasound using magnetostriction is one of the oldest ultrasound technologies that has mostly been replaced by piezoelectricity. But how do these two procedures differ? And to what extent is magnetostrictive ultrasonic cleaning particularly suitable for molds and tools?

With its working principle, ultrasound by magnetostriction is one of the oldest ultrasound technologies. However, in the past, this technology had only a very low efficiency.

Later, piezoelectricity was discovered, which is very cheap and can also be imported cheaply from Asia. For this reason, many companies concentrated on piezoelectricity.

But what exactly are the advantages? And to what extent is magnetostrictive ultrasonic cleaning particularly suitable for molds and tools?


Ultrasound by magnetostriction

We continued our work on magnetostrictive ultrasound technology and developed our Magnasonic ultrasound. This technology is much more effective and above all, unlike piezoelectric sensors, there is hardly any wear and tear.

As a result, there are magnetostrictive ultrasonic cleaning systems that have been working perfectly for 20 years and still use the same ultrasonic transmitter as when they were installed. (Figure 1)

This is not possible with piezoelectric technology. In this case, the lifetime of the transmitters is generally between 4,000 and 6,000 hours.

This means that the transmitters must be replaced every one to two years. This is not the case with our magnetostrictive technology.


The comparison

Magnetostrictive technology is better suited for cleaning molds and tools because;

  • When cleaning molds, temperatures rise to 95 °C, while the temperature for cleaning components is usually 40 to 50 °C. Ultrasonic magnetostrictive technology can be used without difficulty at these high temperatures and for long periods of operation without causing wear to the transmitter.

  • Magnetostrictive ultrasound is a very low-frequency ultrasound. In general, the frequency range of ultrasound in the tanks is between 18 and 20 kHz.

  • Additionally - and this is just as important - we modulate the frequency continuously between 18 and 20 kHz. This means that we do not have a standing wave. (standing waves cause cavitation damage - as can be seen in figure nr. 2)


Very large bubbles for cleaning heavily soiled surfaces

The low frequency has another advantage: very large bubbles are generated with very low frequencies.

What does a large bubble mean? A large bubble contains a lot of energy. These bubbles are created in the liquid and when they rise to the surface they implode and form very strong liquid micro-jets that remove the dirt.

At higher frequencies, I have smaller bubbles which are not as effective for cleaning. With large bubbles, we can clean very dirty surfaces relatively well.

Further info
Product groups:
Periphery, products for plastics processing
    Mold cleaning

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Image of   Marco Höfler

Marco Höfler

FISA Ultraschall GmbH

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