Problems to be considered when selecting ultrasoni

2022-08-16
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Problems that should be considered when selecting ultrasonic cleaning equipment

I. selection of power

the effect of ultrasonic cleaning is not necessarily the same as (power × Cleaning time), ultrasonic cleaning machine sometimes uses small power, and it takes a long time to remove dirt. If the power reaches a certain value, sometimes the dirt will be removed quickly. If the power is too large, the cavitation intensity will be greatly increased, and the cleaning effect will be improved, but at this time, the more precise parts will also produce corrosion spots, which is not worth the loss. In addition, the cavitation at the vibrating plate at the bottom of the cleaning cylinder is serious, and the water spot corrosion also increases. When using organic solvents such as trichloroethylene, there is basically no problem, but when using water or water-soluble cleaning fluid, it is easy to be corroded by water spots. If the surface of the vibrating plate has been damaged, Cavitation corrosion is more serious under high power, so ultrasonic power should be selected according to actual use

second, the choice of frequency

the ultrasonic cleaning frequency ranges from more than ten kHz to 100kHz. When using water or water cleaning agent, the physical cleaning force caused by cavitation is obviously beneficial to the low frequency, which is generally about 15-40khz. For parts with small gaps, slits and deep holes, high frequency (generally above 40KHz) is better, even hundreds of kHz. When cleaning clock parts, use 400kHz. If you use broadband FM cleaning, the effect is even better if there is no response. The biggest possibility is that the connection of the power supply is good

III. use of cleaning basket

baskets are often used when cleaning small parts. Special attention should be paid to the ultrasonic attenuation caused by the eyes. When the frequency is 28kHz, it is better to use eyes above 10mm

IV. selection of cleaning solution temperature

the most suitable cleaning temperature of water cleaning solution is 40-60 ℃, especially in cold weather, if the temperature of cleaning solution is low and the cavitation effect is poor, the cleaning effect is also poor. Therefore, some cleaning machines wrap heating wires around the outside of the cleaning cylinder for temperature control. When the temperature rises, cavitation is easy to occur, so the cleaning effect is good. When the temperature continues to rise, the gas pressure in the bubble increases, causing the impact sound pressure to drop, reflecting the multiplication of these two factors

v. determination of the amount of cleaning fluid and the position of cleaning parts

generally, it is better that the liquid level of cleaning fluid is more than 100mm above the surface of vibrator. Because the single frequency cleaning machine is affected by the standing wave field, the amplitude at the wave node is very small, and the amplitude at the wave amplitude is large, resulting in uneven cleaning. Therefore, the best choice for cleaning items should be placed at the wave amplitude

VI. selection of ultrasonic cleaning process and cleaning fluid

before purchasing the cleaning system, the following application analysis should be done to the cleaned parts: clarify the material composition, structure and quantity of the cleaned parts, analyze and clarify the dirt to be removed, which are the prerequisites for deciding what kind of cleaning method to use and judging whether to use aqueous cleaning fluid or solvent. The final cleaning process needs to be verified by cleaning experiments. Only in this way can we provide a suitable cleaning system, design a reasonable cleaning process and cleaning fluid aligned with the middle direction. Considering the influence of the physical characteristics of cleaning fluid on ultrasonic cleaning, steam pressure, surface tension, viscosity and density should be the most significant factors. Temperature can affect these factors, so it will also affect the efficiency of cavitation. Any cleaning system must use cleaning fluid

when selecting cleaning solution, the following three factors should be considered:

1. Cleaning efficiency: when selecting the most effective cleaning solvent, experiments must be done. If ultrasound is introduced into the existing cleaning process, the solvent used generally does not need to be changed

2. simple operation: the liquid used should be safe, non-toxic, simple to operate and long service life

3. cost: the use cost of the cheapest cleaning solvent is not necessarily the lowest. In use, we must consider the cleaning efficiency and safety of the solvent, how many workers can be cleaned with a certain amount of solvent, and then use the traditional manufacturing technology to process the parts with the highest utilization rate. Of course, the selected cleaning solvent must achieve the cleaning effect and be compatible with the workpiece material being cleaned. Water is the most common cleaning solution, so the system using water-based solution is easy to operate, low-cost and widely used. However, some materials and dirt are not suitable for aqueous solutions, so there are many solvents to choose from

VII. Different cleaning fluids, cleaning systems to be distinguished

aqueous systems: usually composed of open tanks, in which the workpiece is immersed. The complex system will be composed of multiple tanks and equipped with circulating filtration system, rinsing tank, drying tank and other accessories

solvent system: most of them are ultrasonic vapor phase grease removal cleaning machines, which are often equipped with waste liquid continuous recovery devices. The ultrasonic vapor phase grease removal process is completed by an integrated multi tank system composed of solvent evaporation tank and ultrasonic immersion tank. Under the combined action of hot solvent vapor and ultrasonic agitation, oil, grease, wax and other dirt dissolved in solvent are removed. After a series of cleaning procedures, the workpiece is hot, clean and dry

VIII. Treatment of cleaning parts

another consideration of ultrasonic cleaning is the loading and unloading of cleaning parts or the design of tooling for placing cleaning parts. When the cleaning parts are in the ultrasonic cleaning tank, neither the cleaning parts nor the cleaning parts basket shall touch the bottom of the tank. The total cross-sectional area of the cleaning parts cannot exceed 70% of the cross-sectional area of the ultrasonic tank. Rubber and non rigid plastic will absorb ultrasonic energy, so such materials should be used with caution when used in tooling. Special attention should also be paid to the cleaning parts of insulation. The efficiency of even the best ultrasonic cleaning system will be greatly reduced if the tooling basket is not designed properly or the workpiece is too heavy. Hooks, shelves, and beakers can be used to support cleaning parts

IX. clarification of cleaning time, workpiece type and quantity

considering that the working mode of the machine is fully automatic, semi-automatic and manual. Machine size and cost

X. other parts that clean a lot of dirt generally need to be pre cleaned by immersion, spray and other methods. After removing most of the dirt, and then cleaning the remaining dirt with ultrasonic, the effect is good. If small objects and objects (parts) with complex shapes are cleaned, they can be cleaned evenly if they are cleaned or rotated and vibrated while using ultrasonic radiation

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