When performing properly an ultrasonic cleaner should give consistent results over time. Equipment size and ultrasonic operating frequency – or frequencies in the case of multi-frequency units – are specified based on users’ requirements. Maintaining performance consistency in turn requires users to monitor the ultrasonic cleaner and take steps to correct malfunctions or unacceptable deviations. Many of these performance checks can be accomplished in-house following procedures outlined in user manuals. On occasions where ultrasonic cleaner repair cannot be done in-house, the equipment should be returned to the manufacturer or authorized service provider.
Ultrasonic cavitation is caused by the implosion of microscopic bubbles in the ultrasonic cleaning solution. Bubbles are created by ultrasonic transducers mounted on the ultrasonic cleaning tank. The number of transducers and their position on the tank is governed by the size of the ultrasonic cleaning unit. When the system is operating properly there is a hissing sound as the bubbles implode on parts being cleaned. Moving waves will be observed on the surface of the solution.
Standard Operating Procedures
Always follow the manufacturer’s operating and maintenance instructions.
Degas fresh cleaning solutions by using the unit’s degas mode for approximately 10 minutes. Otherwise operate the unit without a load for 45 minutes. If it is equipped with a heater, turn it on to speed up the degas process, which is signaled when air bubbles stop rising to the surface.
As the unit operates the temperature of the cleaning solution will increase due to ultrasonic energy and can reach 60˚C (140˚F) or higher. If higher cleaning temperatures are required the ultrasonic cleaner’s heater thermostat can be set accordingly.
Constantly monitor the level of cleaning solution in the tank. Remember that every time you remove a basket of cleaned parts you remove solution coating the parts. Heat causes evaporation, which can be slowed by covering the tank during operation. This will also muffle noise. Damage can result when the tank is operating at less than capacity (either to the “fill” line or 2/3 full). Overfilled tanks will not clean satisfactorily.
Some Examples of Diagnostic and Correction Steps
Each equipment manufacturer will have specific instructions for diagnosing and correcting malfunctions. The following examples are excerpted from validation steps for the Elmasonic S series ultrasonic cleaners available from Tovatech.
- Conduct an aluminum foil test on new equipment to establish a baseline from which you can judge cleaning power performance on a regular basis (see below). Cut a strip of household aluminum foil and, wearing textile gloves, dip it in a degassed operating bath for one minute (1/2 minute without a basket in the tank). At the end of the test you should observe a surface texture that could look like pin pricks or see holes in the foil. Identify the foil with a marking pen and store it in a transparent sleeve for later use.
- Check the actual temperature of the cleaning solution against the set temperature on a regular basis. Once the solution has reached the set temperature turn the unit off and use a digital thermometer to get an independent reading. This temperature should not deviate from the set temperature by more than 2 – 3˚C. If excess deviations continue to occur contact the supplier or manufacturer.
- Ultrasonic cleaning slows or stops. This can be due to an electronic malfunction and is indicated by a lack of hissing and surface wave action and/or a signal light on the unit control panel. First try a reset by turning off the unit and disconnecting it from the power source. If reconnecting does not solve the problem or the malfunction continues to occur, return the unit to an authorized service point or manufacturer for repair.
- Malfunctioning transducer systems can be indicated
-by a complete system breakdown in which case the generators turn off and all control panel diodes go dark. The unit should be returned to an authorized service point or manufacturer OR
-by reduced cleaning power in the tank. In this case the transducers may not turn off and operating diodes may remain illuminated. Cleaning power can be checked as follows on a regularly scheduled basis:
Use a wattmeter between the unit plug and the wall outlet. Operate the tank without the heater on. The wattmeter reading should not deviate from the unit’s operating instructions power by more than ± 15%. If cleaning is satisfactory you can run the unit at lower power but inspect results more thoroughly.
Conduct the aluminum foil test and compare the results to those exhibited from the initial test. If the effect on the foil is diminished, it will indicate reduced power.
- Check timer accuracy on a monthly basis. Set the timer for 15 minutes and switch on the unit. Use a stopwatch to measure any deviation. It should be less than 5% (45 seconds). If results are not satisfactory contact the manufacturer.
In summary, these and other regular performance checks can help your ultrasonic cleaner deliver optimum cleaning action. The ultrasonic cleaning specialists at Tovatech are ready to provide advice on selecting and using equipment tailored to your operations.