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Ultrasonic Cleaning Tips for Avoiding Parts Damage

The broad acceptance of ultrasonic cleaning is due to its proven ability to safely and quickly remove contaminants from products ranging from engine blocks to surgical implants. But safely using sonic energy requires an awareness of the process and the many points to consider when establishing your cleaning procedures. That’s because improper cleaning procedures can result in parts damage.

Sonic cleaning action itself is quite amazing. Consider that the implosion of the microscopic bubbles in the cleaning liquid creates a temperature of 5,000°C (more than 9000°F) or similar to the surface of the Sun! And the pressures created range from 15,000 to 150,000 psi. Yet these extremes are “harmless” to objects being cleaned because they dissipate instantaneously, affecting only the contaminants on part surfaces.

You note that we put quotes around harmless in the preceding paragraph. Following is a brief presentation on ultrasonic cleaning tips you should follow for avoiding parts damage.

For example, ultrasonic cleaning equipment is designed to operate at a specific frequency such as 25, 37, 40, 45 or 80 kHz. Some models offer dual-frequency capability such as the Elma TIH130MF2 that operates at a user selected 25 or 45 kHz, or the PH750EL that operates at 37 or 80 kHz. Units with higher frequencies are available.

Why is frequency important? The lower the frequency the larger the cavitation bubbles and the more violently they implode. (You would be hard-pressed to visually determine the difference in size.) That’s why low frequencies are ideal for removing gross contaminants from parts such as engine blocks but why they are not good for delicate or highly finished parts such as PCBs or highly polished surfaces where higher frequencies should be employed. If you clean a variety of products consider a dual frequency unit such as those mentioned above.

Keep in mind is that cavitation action does not occur evenly throughout the cleaning bath unless the equipment is equipped with a sweep mode. Sweep slightly varies the frequency above and below the assigned frequency by approximately ±3 kHz to eliminate hot spots and standing waves that can damage surfaces. Another value of the sweep mode is that it eliminates the danger of damage to small or delicate parts that could start to vibrate at the resonance of the transducers.

Photomicrograph of an imploding cavitation bubble

Another point to consider is cleaning solution chemistry and its effect on the products you are cleaning. Solutions are generally classified as acidic, neutral or alkaline, and a wide variety of formulations are available. Selection is based on what you are cleaning and the type of contaminants being removed. Check our cleaning solution page for popular formulations or contact us to discuss your particular cleaning challenges.

Our final point for this post relates to the parts being cleaned. When practical, metal parts should be of the same composition. That is, don’t mix brass and bronze with steel or aluminum components. This is because different metals or alloys may result in discoloration on the surfaces where they come in contact with each other. In addition, metals and alloys respond better to cleaning solution chemistries formulated for them. Note that chromium-plated parts should not be sonically cleaned.

To the extent possible keep products from contacting each other. Sonic vibration could cause surface damage. For more on this topic see our post on parts positioning.

For more information on how to avoid parts damage contact our ultrasonic cleaning experts at 973-440-2191. You can also discuss equipment, processes and cleaning solution formulations to meet your requirements.

FREE GUIDE TO ULTRASONIC CLEANING APPLICATIONS

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