Basic Concerns with Ultrasonic Cleaning | Part 4: Transducer and Load Positioning
Ultrasonic cleaning is a versatile method for precision cleaning a broad range of objects. While it involves a simple process, there are several factors to consider for ensuring the best results. In this series of blogs, we’re examining seven key factors that can impact ultrasonic cleaning.
In this article, we look at how the performance of the ultrasonic cleaning process is affected by the positioning of the transducers and the load to be cleaned.
Transducers for Ultrasonic Cleaning
Transducers are at the heart of how ultrasonic cleaners work. They convert electrical energy from a generator into sound waves that radiate through the liquid in a cleaning tank. This radiation causes cavitation that cleans the objects in the tank.
Modern transducers are manufactured from lead zirconate titanate, a piezoelectric material which expands and contracts when electrical energy is applied to it. The rapid expansion and contraction of the material causes the adjacent surface to vibrate, introducing acoustic waves into the cleaning fluid in the tank.
Transducers operate in a similar way to radio speakers, except they function at ultrasonic frequencies (usually 40kHz) and transmit acoustic energy to a liquid rather than to air.
The number of transducers required for an ultrasonic cleaner depends on the size and shape of the tank, the objects to be cleaned and the contaminants that need to be removed. For example, in large tanks, multiple transducer modules can be distributed across the tank to ensure more even cleaning.
Ultrasonic cleaner transducers can be of two types.
Direct bonded transducers are fixed to the tank with a high temperature adhesive.
Transducer modules are normally fitted to the bottom of tanks, but can be fitted to the tank sides if, for example, a tank is deep and narrow.
Tanks with direct bonded transducers are the most straightforward option when choosing a standard ultrasonic cleaner as the transducers are fitted in the manufacturing process and the tanks require no further design or customization before use.
Transducers can also be fitted into a stainless-steel container that is submerged into the cleaning liquid.
Immersible transducers are required for tanks of unusual shapes or very large sizes. They can also be used to convert a normal tank into an ultrasonic cleaning tank or for cleaning applications that require additional ultrasonic power to clean effectively.
The containers for immersible transducers can be bulk-head or free-standing containers. Bulk-head containers are fixed to the tank with bolts. Free-standing containers can rest on the bottom or be hung on the sides of the tank.
Experts can advise on the number and type of immersible transducers required to meet specific cleaning requirements.
Positioning the Load in the Tank
The way the load is positioned in the tank is critical for ensuring every contaminated part can be cleaned effectively. Factors to consider include how the load will be held in the tank and how it is positioned with respect to the transducers.
Fixtures for Holding the Load
The load to be cleaned must be suspended in the cleaning liquid.
For non-automated systems, this is usually done with a stainless-steel mesh basket. It is possible to use baskets made from non-conductive materials, such as plastic, but this will not produce the same results. It is also possible to suspend a part in the tank using string or wire.
For automated cleaners, the load is usually placed in a mesh basket that is picked up or held by a fixture designed for the cleaner. The holding fixture might be hooks or hangers, magnetic holders, rotating platforms or some other custom frame or fixture.
Positioning the Load
Load positioning should follow these guidelines:
- The load should be as close as possible to the transducers to ensure maximum exposure to the ultrasonic waves. However, the load should not be in contact with the bottom or sides of the tank or with an immersible container as this impedes the ultrasonic energy from reaching the load.
- The load should be arranged so that all surfaces that need to be cleaned are accessible. This is critical for parts with intricate configurations or that are soiled with hard-to-remove contaminants.
- The entire load should be submerged in the cleaning liquid. All surfaces that need to be cleaned must be in contact with the liquid.
- Any air pockets, for example, in tubes, should be removed as they will prevent ultrasonic waves from reaching the area in the air pocket. The part may need to be agitated or rotated to remove air pockets.
For automated cleaners, the fixtures will ensure that the load is held in the optimum position for cleaning.
For non-automated cleaners, a mesh basket will prevent the load from touching the bottom of the tank. If the load is positioned in the tank using another method, it’s important to check that it meets the guidelines for effective cleaning.
Wrapping Up
The number and placement of the transducers in an ultrasonic cleaning tank and the way that the load is positioned in the tank can have a significant impact on the efficacy of the cleaning process.
UPC can provide advice both on the type of tank and transducers that are best suited to your cleaning requirements and on how to position the load in the tank for optimum results.
If you have more questions, please feel free to get in touch and send in samples so we can determine the right ultrasonic power cleaner for you. And look out for the next post in this series in which we explore how the ultrasonic output frequency affects the cleaning process.
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We offer a range of our most popular ultrasonic cleaners for rent on a 30-day try-before-you-buy basis or as a long-term rental option.
