The ultrasonic wave is a frequency above 20kHz sound wave, but the custom takes about 10kHz high-frequency sound wave also as the ultrasonic wave. Ultrasonic wave is a kind of mechanical vibration wave, which belongs to longitudinal wave, and the direction of vibration is consistent with the direction of propagation.
The ultrasonic cleaning of hardware parts is mainly based on its cavitation effect, that is, when the ultrasonic wave propagates in the liquid medium, due to the mechanical vibration of the elastic medium, it causes the medium to produce alternating dense and sparse distributions, where the dense places are subjected to enormous pressure and the sparse places are subjected to tension, and the pressure and tension in the medium are alternately changed, when the liquid can not withstand such a strong tension, it will be torn and the formation of many instantaneous vacuoles (cavitation bubbles). Because the ultrasonic vibration frequency is very high, the process of compaction and thinning is changing constantly. So this kind of cavity will be squeezed and broken in a short time when the medium changes from thinning to compaction. The formation and rupture of such vacuoles occur at a rate of tens of thousands to millions of times per second. In the very short time that these small vacuoles are squeezed to break up, the pressure can reach several thousand to tens of thousands of atmospheric pressure, its mechanical energy is very big, produces a formidable impact force, forms the high-speed scouring action to the surface of the parts, the oil, dirt and dust particles on the surface of the parts immersed in the liquid medium are stripped off and fall into the liquid; These weak-binding compounds break down into liquids; moreover, a large amount of energy gathered by the cavitation effect is rapidly released in a small area, causing the temperature of that small area to rise, in turn, the solubility of some substances increased, accelerating the dissolution. It can be seen that ultrasonic cleaning not only has a physical effect but also has a chemical effect.
The ultrasonic generating mode is the same as ultrasonic processing equipment. It can be divided into the magnetostrictive type and the piezoelectric crystal type. The difference is that in an ultrasonic cleaning machine, the transducer is no longer connected to the processing head, but is either connected to the nickel chassis of the cleaning tank (cleaning container) or immersed directly in the liquid medium in the cleaning tank. The former transmits the ultrasonic vibration to the liquid through the vibration of the chassis, while the latter transmits the ultrasonic vibration to the liquid directly by the transducer, and the parts are immersed in the liquid for cleaning.
Ultrasonic cleaning is mainly used to clean metal parts with small seams, narrow grooves, deep holes, blind holes, and other dead corners because such parts of metal parts are difficult to reach by hand or general objects, cleaning solvents can also be difficult to penetrate, and create a flow, making it difficult to clean up these so-called narrow areas or dead ends, while ultrasound can penetrate any small area, give full play to its unique cleaning function.
The position of the transducer in the ultrasonic cleaning machine should consider keeping the standing sound wave stable in the cleaning tank and keeping the parts in the belly of the wave. Therefore, the height of the cleaning fluid can be changed by adjusting the amount of cleaning fluid, and then the parts can be moved to the belly of sound intensity, and the interference of standing sound waves is minimum.
Cleaning fluid should be based on the different hardware parts to be cleaned to choose, water is the most commonly used cleaning fluid, it is non-toxic, cheap, and effective, considering that to have a better oil removal effect, also often choose trichloroethene, anhydrous ethanol, acetone, etc. as cleaning fluid.
After any kind of cleaning, especially the corroded hardware parts, must be fully washed, the parts after pickling should also be fully washed with running water, water washing is best to use deionized water, and sometimes tap water can also be used, after washing, dehydrate and dry with anhydrous alcohol, then stand by. For different materials, different pollutants have mature cleaning specifications, as long as the specifications of the process requirements to clean, you can clean the parts thoroughly.