Knowledge | 2022-09-15
A brief talk on ultrasonic cleaning equipment
The ultrasonic cleaning equipment mainly has the generator, the transducer, and the cleaning through three parts. The transducer is the vibrating plate, which is the key part of ultrasonic cleaning. It converts the electromagnetic vibration produced by the generator into the ultrasonic vibration of the transducer itself, and into the cleaning tank to create a vacuum cavity (hereinafter referred to as cavitation), usually placed at the bottom of the tank;
The principle of ultrasonic cleaning
The frequency of ultrasonic cleaning is about 30kHz. Ultrasonic cleaning mainly uses the ultrasonic wave to produce the cavitation effect in the liquid, peels the oil dirt and the oxide skin of the workpiece surface rapidly, and achieves the cleaning goal. When the ultrasonic wave is radiated on the liquid, the instantaneous negative pressure is produced repeatedly and alternately, and cavitation occurs in the liquid during the half period of the negative pressure produced by the vibration, that is, liquid vapor (water vapor, the solvent vapor produced when the solvent oil removal) or dissolved gas into the solution into the cavity, the formation of a large number of non-steady-state micro-bubbles and bubbles (about 50-500 & mu; m in diameter), and then, during the half-cycle of positive pressure, these bubbles and micro-shock waves with instantaneous pressure up to hundreds or even thousands of MPA burst due to violent collision, causing the air pressure around the bubble to rise to hundreds of MPA, it produces strong agitation to the solution and forms the impact force to wash the dirt on the surface of the workpiece, so that the dirt in the deep pits and pores of the parts can be removed, thus speeding up the cleaning process.
Characteristics of ultrasonic cleaning
(1) ultrasonic waves can be used in solvent deoiling, chemical deoiling, electrochemical deoiling, and pickling to remove oil, rust, and film.
(2) ultrasonic wave is especially suitable for fast and continuous pickling processes, such as pickling in continuous galvanizing pretreatment of wire (Iron Wire).
(3) ultrasonic wave is not only suitable for steel parts but also suitable for surface cleaning of aluminum alloy parts.
(4) the concentration and temperature of the ultrasonic cleaning solution are correspondingly lower, and the cleaning time is also shorter.
(5) ultrasonic cleaning has high efficiency and high speed, especially can protect the base metal from corrosion and prevent hydrogen permeation caused by cathodic electrolysis.
The factors that affect the effect of ultrasonic cleaning
Ultrasonic cleaning liquid concentration should not be too high, otherwise, it will hinder the spread of ultrasonic, and affect the cleaning effect. Use a solution with a lower concentration than the usual oil removal solution, resulting in better results. But it is not simply to dilute the original solution directly, the composition and proportion should be selected reasonably.
If only use water to clean, at about 50 & deg; C, the water washing ability is the strongest, and the temperature is too high because the water produced a large number of bubbles hindering the spread of ultrasound, thus reducing the cleaning effect. A similar phenomenon can be seen in the cleaning of oil removers. Therefore, according to the solution composition, the temperature must be controlled in the optimal range.
Ultrasonic has the effect of vibration and coagulation on particles suspended in solution, which can improve the cleaning ability, but also affect the cleaning effect by contaminating the surface again. Therefore, it is necessary to regularly filter the tank fluid, and remove grease, and solid dirt, the best conditions to set up a continuous filter device.
Especially for the accumulation of oxide scale or metal dissolute in the pickling solution, the effect of ultrasonic radiation is decreased and the cleaning quality is affected. Therefore, the pickling solution should be updated frequently.
For small parts, the use of a net basket aperture should be appropriate, if the net aperture or hole plate basket aperture is too small, it will weaken the ultrasonic intensity, and reduce the cleaning effect. If the aperture is too large, the workpiece is easy to leak. Therefore, it is best to set a non-perforated metal sheet (about 0.5-1mm) at the bottom of the net basket, which can be penetrated by ultrasound to clean the workpiece in the net basket.
Because the ultrasonic is a straight-line transmission, if the workpiece is static, the part of the ultrasonic deep concave, blind holes, and the back of the area often reach, that is, can not be cleaned clean or uneven cleaning. Therefore, the workpiece should be rotated in the groove, so that all parts can get ultrasonic radiation, to achieve the desired effect.
The technical parameters such as the frequency and intensity of ultrasonic oscillation should be selected reasonably, and the ultrasonic wave with high frequency and low vibration radiation should be used for small parts with complex shapes, and the ultrasonic wave with low frequency should be used for larger parts. If the ultrasonic frequency and intensity are insufficient, the solution can not form bubbles, and the surface of the workpiece can not be impacted and clean ineffective dirt.
To sum up, because of its high frequency, strong directivity, strong penetration, cavitation in the liquid, and other characteristics, strengthen the cleaning process, especially, it is more suitable and effective for products with complex shape, fine hole, blind hole, narrow slit and high requirement of surface pretreatment.