The article on effective ultrasonic cleaning basics is kindly presented by Hilsonic Company – a far-famed UK ultrasonic cleaner manufacturer with 12 years of successful track record. The company experts are sharing their knowledge on the aspects having a direct impact on ultrasonic cleaning quality.
The power matters
At frequencies around 400 Hz cleaning efficiency is maintained at a sufficiently large distance from the source of vibrations, while at low frequencies it sharply decreases with increasing this distance, which is caused due to significant absorption of ultrasonic cavitation.
With the increase in power increases the intensity of the ultrasonic vibrations and cavitation improves the cleaning efficiency. However, if too much power is given a sharp rise in the intensity of cavitation in the vicinity of the source of ultrasonic vibrations is observed which contributes to the loss of energy and reduction of purification efficiency. Too high power of ultrasonic vibrations may cause undesirable mechanical damage to the workpiece as well as surface erosion.
Temperature & procedures
With temperature increasing grows the solubility and reactivity of cleaning solution, but only up to certain limits. On one hand, with increasing temperature the solubility of gases in liquid decrease and thereby grows the number of microscopic gas bubbles, cavitation nuclei which are, on the other hand, the vapor pressure increases in the gas bubbles, which reduces the energy of cavitation.
The cleaning solution used in the ultrasonic cleaning procedures should intensively dissolve various types of contamination, preserve cleaning properties, provide low or non-toxic effect, does not have to be make a solvent or corrosive impact on the equipment, basic materials and protective coatings and, of course, be economical.
The effectiveness of the ultrasonic cleaning is influenced by such physical-chemical properties as surface tension, vapor pressure and viscosity. Since the quality of cleaning is increased with decreasing surface tension at the cleaning solution from a cleaning surface of the cleaning solution is expediently added surfactants. The high vapor pressure of the washing liquid cavitation decreases the energy, and it reduces the viscosity of high cleaning efficiency, because it prevents the growth of gas bubbles and oscillatory hampers their movement.
High-quality cleaning rules
With the increase in processing time the cleaning quality is improved. Actually, the cleaning time depends on the size and shape of parts, the state of their surface and the degree of its contamination, the nature of pollution and other factors and is usually determined empirically.
Ultrasonic cleaning can be stepwise and continuous. At step purification items treated successively in several baths with the same or different washing solutions, while continuously moving in the same tank, wherein the detergent solution is fed forward movement of parts, thus cleaning takes place in different zones of the bath solution varying degree of contamination. Typically, the time frame for ultrasonic cleaning ranges from several seconds to several minutes. After removal from the bath the items are dried in the vapor of a solvent or a stream of pure gas. To eliminate the formed during drying stains, the details are rinsed in pure solvent.