In recent years, the process of using ultrasonic cleaning for the cleaning of manufactured parts has gained in popularity. While very effective at removing contaminants from small crevices in complicated parts, ultrasonic cleaning has some very different performance demands for the baskets that hold the parts through this particular cleaning cycle in comparison to vapor degreasing or even a typical aqueous wash process.
What are these performance demands? How and why do they differ from other wash processes?
To answer these questions, it is important to first know how ultrasonic cleaning works.
A Basic Overview of Ultrasonic Cleaning
In an ultrasonic cleaning process, the part or parts to be washed are placed inside of a chamber that has been filled with a specialized solution that can be aqueous or organic-based. Once the part or parts are suspended in the solution, an ultrasound transducer device is activated.
The vibrations from the transducer cause the solution to “tear” itself apart and create millions of microscopic voids in the solution (a process known as cavitation). When the solution seeks to fill these miniature empty spaces, the resultant collapse releases a great amount of force and thermal energy in a very small area. In a way, this is similar to how the air separated by a bolt of lightning rushes back to fill the void left behind by said bold, creating the characteristic loud thunderclap associated with a lightning strike, along with intense heat and air pressure.
The higher the ultrasonic frequency used in the cleaning cycle, the less distance there will be between cavitation points, allowing for more thorough cleaning of fine details and points on the part.
One reason why many manufacturers prefer ultrasonic cleaning to vapor degreasing or standard aqueous parts washing is that ultrasonic cleaning minimizes the need for excessive amounts of harsh chemical solutions as a part of the wash process. This makes complying with certain environmental protection regulations regarding emissions easier.
Basket Design Considerations for Ultrasonic Cleaning
Some of the things that someone designing an ultrasonic cleaning machine might need to take into account include:
- Corrosion Resistance. Depending on the cleaning solution used for the ultrasonic cleaning machine, any basket placed in the machine may need different levels of corrosion resistance. However, because lower concentrations of chemicals are used for cleaning, corrosion is not often as much of a factor as it would be for vapor degreasing.
- Ability to Resist Vibrations. The vibrations involved in an ultrasonic cleaning process can put a lot of strain on a manufactured object over the course of repeated exposure. The wires of a wire basket need to be well-secured against failure with comprehensive welds so that individual wires do not become separated from the rest of the basket.
- Drainage. Once the part is removed from the solution, any solution left on the part needs to be able to drain as completely as possible as quickly as possible. This is one reason why many ultrasonic cleaning baskets are made of wire mesh. With wire mesh, open area of the basket is easy to control, with large gaps and rounded wires keeping liquids from settling on the basket.
- Ability to Hold Part in Place without Excessive Contact. In an ultrasonic cleaning process, the solution can only clean areas of the part that are exposed to contact with the solution. Cavitation cannot occur between two solid objects. Because of this, it is important that an ultrasonic cleaning basket does not cover up too much of the surface area of the part(s) being washed. On the other hand, parts need to be held securely so that they do not loosely bounce around, as that can cause abrasion damage.
- Limiting Risk of Abrasion Damage. Speaking of abrasion damage, delicate parts with a low scratch resistance need to be protected from scratches that can be caused by hitting the sides of a basket as well as the actual contact points used to hold parts in place. To this end, a basket for ultrasonic cleaning can be dipped in a soft coating such as thick PVC. This coating should be soft enough to absorb the force of impact without damaging the part(s) being washed, but also resist transferring material from the coating to the part. Also, any coating used needs to be able to survive the chemicals used in the ultrasonic cleaning process.
Building a Better Ultrasonic Cleaning Basket
Marlin Steel’s engineers have years of practical experience in designing ultrasonic cleaning baskets with tight tolerances and for a variety of parts with unique needs. Combine this with computer modeling and virtual stress-testing, and these professionals can make the perfect ultrasonic cleaning basket to meet the exact needs of your particular ultrasonic parts washing process.
To learn more about design needs for baskets to be used in ultrasonic cleaning, contact Marlin Steel today.