Currently, fastener manufacturing companies commonly use various cleaning methods, including immersion heating cleaning, pressure spray cleaning, brush cleaning, and ultrasonic cleaning.

The cleaning principles for immersion heating and pressure spray cleaning involve using liquid to forcefully remove dirt and contaminants from the surface of fasteners. Brush cleaning uses brushes to scrub and remove dirt from fastener surfaces, with the liquid carrying away the contaminants. While these three methods can clean bolts and nuts that have undergone various processes relatively well, they struggle to completely clean oil, grease, and fine particles with strong adhesion, especially in blind holes, grooves, and small openings. Ultrasonic cleaning, on the other hand, can effectively remove contaminants with strong adhesion and achieve the desired cleaning results in blind holes, grooves, and small openings due to its strong penetrating power. Therefore, among these four cleaning methods, ultrasonic cleaning delivers the best results.

Ultrasonic Cleaning Mechanism

Ultrasonic cleaning achieves excellent cleaning results, which can be understood through its cleaning mechanism. Ultrasonic waves are sound waves with frequencies beyond the range of human hearing, and the frequency range of ultrasonic waves generally falls between 18 to 90 kHz. Ultrasonic cleaning is essentially powered by ultrasonic vibration, consisting of an ultrasonic generator and an ultrasonic cleaning device. The ultrasonic generator generates high-frequency electrical signals, supplying the ultrasonic cleaning device with the necessary ultrasonic power. The transducer within the device converts this electrical power into ultrasonic wave energy, converting high-frequency electrical energy into mechanical energy, resulting in ultrasonic vibration. Under the action of ultrasonic vibration, the cleaning liquid alternates between a sparse and dense state. In the dense state, the liquid experiences positive pressure, while in the sparse state, it experiences negative pressure. The cleaning liquid generates numerous microbubbles under ultrasonic vibration, dissolving in the liquid and adhering to solid surfaces. As the bubbles grow in the sparse state, they absorb more gas from the liquid. When they suddenly collapse as they close in the dense state, kinetic energy concentrated within the small volume is rapidly released, creating a spherical shockwave that exerts thousands of atmospheres of pressure. This cavitation process occurs at the same frequency as the ultrasonic waves. For example, with a frequency of 20 kHz, cavitation occurs with 20,000 shockwaves per second striking the surface of objects. This pressure causes the cleaning liquid to flow into fasteners, effectively stripping away dirt and contaminants from bolt surfaces, much like a powerful brush scrubbing dirt from bolt surfaces. This action, particularly in hard-to-reach blind holes, grooves, and small openings, is the erosive effect of cavitation. Additionally, cavitation action accelerates the movement of liquid at the liquid-liquid interface, dispersing and creating high-speed micro-jets near the bubbles. This makes it easier for contaminants adhering to fastener surfaces to detach, corresponding to the emulsification and agitation effects of cavitation. In summary, ultrasonic cleaning primarily relies on the cavitation effect produced by ultrasonic waves.

Ultrasonic Cleaning Process

Choosing the right ultrasonic cleaning process can significantly enhance cleaning effectiveness. Fastener manufacturing companies typically use the SLW-Q series ultrasonic cleaning production line for coating purposes, suitable for cleaning and degreasing fastener products. They use a degreasing agent such as HJ-921, set the rough spray and ultrasonic cleaning temperature at 60±5°C, perform three cleaning cycles, and three-stage drying, with a drying temperature of 105±15°C and a conveyor belt travel time of more than 45 to 60 minutes. Key process points include controlling the concentration of the degreasing agent at 10-12Pt, analyzing and adjusting the degreasing agent concentration in the cleaning tank every 4 hours, with approximately 10kg of degreasing agent added to increase the concentration by about 1Pt. It's important to note that it's preferable to replace the cleaning liquid every month. In the production area, fasteners that fall on the floor after ultrasonic cleaning are considered defective.

Advantages of Ultrasonic Cleaning

① High Quality: Ultrasonic cleaning technology improves the cleanliness of fasteners, resulting in better cleaning effectiveness and higher coating quality. It particularly excels in removing contaminants from hard-to-reach areas like blind holes, grooves, and small openings.

② High Efficiency: Ultrasonic cleaning machines are suitable for mass production, with fast cleaning speeds, saving time. Fasteners are loaded from the feeding hopper and vibrating tray into the coarse spray area, undergoing three cycles of ultrasonic cleaning and drying, significantly increasing production efficiency.

③ Low Labor Intensity: Ultrasonic cleaning can complete the entire cleaning-to-drying process on the production line in one go, reducing intermediate steps and lowering labor intensity.

④ Low Cost: Ultrasonic cleaning machines are equipped with automatic circulation and filtering devices, ensuring cleaning quality and extending the lifespan of the cleaning solution. While the initial investment in ultrasonic cleaning may be substantial, the cost is quickly recouped, making it a cost-effective option in the long run.

⑤ Guaranteed Production Schedule: The application of ultrasonic cleaning technology effectively improves the supply cycle and lays a solid foundation for coatings (such as Dacromet and zinc-nickel alloy), providing an effective approach to enhancing the quality of bolts and nuts.

Peak Fasten Technologies is a professional custom fasteners supplier in China since 2010. We are dedicated into designing, producing and delivering high quality custom bolts, custom nuts and rivets to global market with professional engineers in all processes including design, structure, production processes, quality control etc. Please feel free to contact us if there is any query or bottleneck problems for connection or fastening issue in your industry.