Ultrasonic cleaning is a process that begins when high-frequency sound waves are emitted. The waves become alternating high- and low-pressure waves inside the cleaner's chamber that create tiny bubbles or cavities that eventually burst. The bursting action provides gentle scrubbing known as cavitation. During cavitation, soiled surfaces are cleaned as they come in contact with the bubbles.
You can achieve optimum cleaning results when cavitation takes place under certain conditions. Use a cleaner made with a degassing feature to remove gas from the cleaning solution. The bubbles that form will have a vaccuum effect and act as a suction device against the surface allowing better cleaning.
Safely maintain ultrasonic cleaners by using perforated or mesh trays to suspend your items in order to prevent transducer damage. The transducers that emit the high-frequency sound waves are usually located along the bottom of the cleaning chamber, and can therefore be damaged if items are placed directly on the bottom surface of the cleaner.
To get the most from your investment in an ultrasonic cleaner you should avoid practices that degrade performance. But because mistakes occur you also need to know how to remedy situations that may arise due to improper use, or in the case of cavitation erosion postpone its onset.
A question we get here at Tovatech is how to avoid rust films on ultrasonic cleaning tanks. Elma ultrasonic cleaners have stainless steel tanks, which under normal conditions do not rust. Instead, rust films are introduced as a deposit either from ferrous products being cleaned or from tap water used in the tank. Rust stains can be avoided by regularly cleaning the tank surface using a suitable cleaning solution such as elma clean 60 or 215 to remove deposits before they have the opportunity to stain the tank surface. If stains are present, an alternative is to operate the cleaner in a heating mode with water plus the cleaning solution.
Under no circumstances should scouring media be employed in any tank cleaning operation.
Another detriment to performance is a mineral deposit (also called furring) that can occur around heating elements when ultrasonic baths are operated at high temperature. These deposits are caused by highly calciferous water in contact with hot surfaces. Furring – as well as heat-caused discoloration of the tank – can be minimized by continuous circulation of the heating bath to avoid hot spots near the heaters. A recommended practice is to turn on the ultrasound as the bath begins to heat. This helps ensure temperature distribution is equal throughout the bath. But if furring or discoloration occurs the remedy and caution are the same as for removing rust films.
Pinholes are a more serious concern for ultrasonic cleaning tanks. These can be caused by mechanical abrasion if metal parts being cleaned, or if metal parts containers, are in direct contact with the tank surface. To avoid this always use a basket when cleaning such parts and be sure the basket does not contact the tank floor or walls. Highly acidic baths can also cause pinholes. If such acidic solutions are necessary they should be put into a special container that in turn is placed in the ultrasonic cleaning tank filled with water. Note that pinholes resulting from improper use of ultrasonic cleaning tanks may void warranties.
A fourth maintenance tip deals with cavitation erosion that can occur in the areas around the transducers. Cavitation erosion is a natural byproduct of ultrasonic cleaning and, depending on how the units are used, will sooner or later occur to the point where the tank will leak. To postpone this institute regular tank cleaning to remove abrasive particles that fall from objects being cleaned. Ultrasound moves these particles around the tank bottom where they have the effect of small drills that damage the tank floor. As above, highly acidic cleaning solutions can likewise damage the steel, as can placing items being cleaned directly on the tank floor. Another good practice is to maintain cleaning fluids at the proper level for the particular tank.