Knowledge | 2022-06-27
ultrasonic washer for optical lens
In optical cold processing, how is ultrasonic cleaning achieved the goal of cleaning it? In general, the cleaning process is named after the drying method, such as the IPA process, which is a cleaning process using IPA (isopropanol) steam for dehydration and drying, the pure water process refers to the use of hot pure water or cold pure water slow lift dry way to dry the cleaning process. Of course, there are other ways to name things. Through continuous change and development, the cleaning process in optical cold processing is mainly the IPA process and pure water process.
The IPA process consists of four steps: washing, rinsing, dehydration, and drying.
Because the washing process is divided into solvent-based cleaning and water-based cleaning, there are different processes: first solvent cleaning, solvent steam drying, and then water-based cleaning; there are also first solvent cleaning, and then use an emulsifier to dissolve the solvent, for water-based cleaning. The latter is smoother, more compact in the process, the equipment requirements are simple. After washing the surface of the lens will not have a firm combination of dirt, only some detergent, and a loose dirt mixture.
As we know, inorganic optical glass is a supercooled molten material with no fixed molecular structure. Its structural formula can be described as a network of silicon dioxide and some metal oxides. Its skeleton structure is a siloxane covalent bond with large bond energy, and its periphery is an ionic bond formed by oxygen and metal ions with small bond energy and is easy to break. Due to the interaction of ultrasonic field and chemical detergent, some materials with low content of siloxane bond or low peripheral bond energy are easy to change during the cleaning process and lead to a poor washing effect. Therefore, it is very important to select the mild detergent, the appropriate detergent concentration, temperature, ultrasonic power, and washing time to ensure the quality of lens cleaning.
The use of water will be washed after the lens surface detergent and dirt dissolution, a removal process is known as rinsing. The factors that affect the rinse effect are as follows: the Rinse performance of the detergent, the purity, temperature and fluidity of the rinse water, ultrasonic frequency, etc. . Generally at 40KHz, at room temperature, the conductivity of 0.1 mm of pure water can guarantee the requirements of rinsing.
The cleanliness of the lens surface after rinsing should be consistent with that of the rinsing water. When it enters the IPA, although the IPA and pure water can carry on the infinite miscibility, under the function of the ultrasonic wave, this kind of miscibility can carry on more quickly, and thoroughly, thus, the state of the lens surface is the same as that of IPA after miscibility. This process is called dehydration. Therefore, the main factors affecting dehydration are the purity of IPA, ultrasonic frequency, and dehydration time. In general, the lowest concentration of IPA is higher than 97%.
The dehydrated lenses are dried in the IPA steam tank. The structure of the steam tank is as follows: the lower part of the tank is IPA liquid, surrounded by a high boiling point oil heating chamber, and the upper part is a condensing zone surrounded by several rings of condensing tubes, the lenses are driven by a chain-driven bracket and run in a drying tank. The drying principle and process are as follows: the steam tank IPA boils under the heating of high-temperature oil, the steam enters the condensing zone upward, and forms the steam zone with relatively stable concentration and temperature in the condensing zone, when a dehydrated lens with liquid IPA on the surface enters the vapor zone, the vapor in the vapor zone condenses and liquefies on the surface of the low-temperature lens, washing the surface of the lens like a shower, when the surface temperature of the lens is the same as the temperature of the vapor, no longer attached to the liquid IPA, but all converted to IPA. At this time, the lens under the drive of the bracket rises back to the condensation area, in this process, because of the gradually lower temperature, the lens surface IPA vapor condensation liquefaction, the liquefied IPA leaves the lens partly under the action of surface tension and gravity, partly volatilizes away from the lens surface when the fixture radiates heat, and after the above process, the lens surface is dried. Thus, there are many factors affecting drying: IPA purity, drying position, chain lifting speed, the water temperature of the chiller, condensing stroke length, drying time, fixture material, shape selection, and so on.
The above is a brief introduction to the four processes of the IPA process. The pure water process consists of three processes: washing, rinsing, and drying. Washing and rinsing are the same as the IPA process and are not repeated. The difference is drying. There are two ways to dry: hot pure water, Slow Princess Thyra of Denmark, and cold pure water.
When the resistivity is more than 15MM, the surface tension can reach the maximum at a certain high temperature. After rinsing the lens immersed in it, the surface is not wetted. The pure water quickly shrinks into a ball on the surface and leaves the lens. The dehydrated lens is dried under filtered hot air. Therefore, the purity of water, temperature, slow pulling speed, the tilt of the workpiece, and the cleanliness of hot air during the drying is very large.
The process of cold pure water drying is very simple: after rinsing through pure water, the lens is put into the centrifugal drying machine, when the workpiece is in balance, start the drying machine, use the principle of centrifugal separation to separate the pure water on the surface of the lens to dry, satisfactory results can be obtained for lenses with low requirements, and the IPA and site can be saved. But the balance performance of the dryer is very high.
This paper introduces the ultrasonic cleaning technology in optical cold machining, the carrier of the technology is equipment, and a reasonable design, and stable performance of ultrasonic cleaning machine can give full play to the advantages of ultrasonic cleaning technology.