Precision pressing technology of the hottest glass

Glass aspherical precision molding technology

glass aspherical molding process

glass aspherical is much higher than plastic aspherical in terms of refraction, light transmittance, high temperature resistance and other properties. At present, glass aspherical technology is almost blank in Chinese Mainland. At present, the companies with relatively successful processing ratio are: Taiwan Yaguang, Kodak, leybas, Philips of the Netherlands, Olympus of Japan, Hoya, Panasonic, etc, From the current development direction of optical enterprises, glass aspherical surfaces will replace plastic aspherical surfaces in the near future. Now, when releasing products, major digital camera companies will emphasize that the products contain several glass aspheric surfaces, which not only reflects the excellent performance of the camera, but also reflects the strength of a company

equipment

at present, there are two kinds of glass aspherical forming: isothermal and Heterothermal forming (as I know). The so-called isothermal: put the glass rough embryo into the mold, heat and pressurize the multiple molds to soften the glass (note that it is not liquefied), make the glass rough embryo into the shape of the mold, then cool the mold, and take out the product; The so-called Heterothermal molding: it is to heat the glass rough embryo before entering the mold to soften it (not liquefy it), then send it into the molding environment, pressurize the mold to make the glass rough embryo into the shape of the mold, and then take it out after cooling (note that the Heterothermal molding mold has always maintained a constant temperature). Simply speaking, isothermal forming is to heat and cool the mold and wool embryo at the same time, and take them out at the same time; Allothermic molding is to heat the wool embryo separately, cool it and take it out separately, and the temperature of the mold remains unchanged. Isothermal forming equipment relies on PLC to control the solenoid valve to drive the cylinder to work and control the temperature and other modules to work

isothermal molding is controlled by the servo motor, so isothermal molding is relatively simple. In this article, we will focus on the current popular circular isothermal molding. This molding equipment is cheap and simple to operate. It is suitable for processing products with small diameter and high precision. The processing speed of this equipment is between 55s and 80s/2shot (according to the difference of wool embryo). There are 24 to 30 sets of molds on each equipment, Based on this, we can calculate the output of a day: (3600s*24h)/cycle time *2 (2 pieces formed each time). About every day, each machine is set up and summarized the utilization trend of carbon fiber composites in automobile, aircraft and other fields. The preparation processing capacity is more than 2000shot, and the isothermal line is divided into two types: one is composed of eight shafts, the mold does not move, and it is taken out and put in by manipulator. This kind of processing equipment covers a large area, One kind of long processing time (about 27min/piece) is circular molding, which is composed of 24 or 30 groups of molds. The molds can be moved, and the processing time is 55s-80s. It has the advantages of small floor area, large output, high processing accuracy, low equipment and mold costs, but it cannot be processed Ф More than 6 products are still being tried; The molding time cycle at different temperature is about 3min/piece, but only one piece/set can be processed at a time; The advantage of small floor area, which can be processed Ф About 10 lenses, but it is troublesome to take countermeasures and disassemble the mold

annealing

after the lens is formed, it also needs to be cleaned and annealed. The reason for annealing is that the glass is hot and cold during the forming process. The surface shrinkage of the lens is uneven to achieve a win-win situation. The principle of annealing is to slowly heat and cool the lens to make the surface accuracy of the lens reach the value we need. In other words, the surface accuracy of the lens produced without annealing is poor. The annealing time is about 10h ~ 12h (depending on the lens material), and each annealing furnace can anneal about 4000shot each time. Note: the surface of the lens must be clean before entering the annealing furnace. Cleaning conditions of lens: detergent can be used. The general time is 65s and the temperature is about 80 ℃. However, some soft material lenses are directly washed with pure water without detergent

detection:

after the lens is produced, the lens should be sampled and inspected. The sampling frequency is: 1 piece/mold/24h, which is only for the parts that have been normally produced, and the others can be determined according to their stable conditions. The test items include: eccentric machine, interferometer and anti shape instrument. The first two are used to detect the eccentricity of the lens. This kind of test can be detected before annealing. The vast majority of Companies in the latter use British Taylor Hobson to detect the surface roughness of the lens. This kind of test can only be detected after the lens is annealed, but it can also be detected before annealing as a reference. All testing equipment is generally very precise, and any action or environment may have a negative impact on the equipment and testing accuracy. The appearance of the lens needs full visual inspection twice. The first time is to take the lens out of the mold. If it is found that the appearance is bad, the mold should be repaired in time. The second time is to check the mold:

because this equipment is isothermal cycle, the processing of each mold is about 100shot a day, which means that this mold has to undergo 100 times of rapid cooling and heating every day, so the key to making a good product is the mold, At present, the mold material is generally tungsten carbide. The service life (normal use) and pleasant communication and exchange of general molds can reach 10000 ~ 30000 molds (excluding mold surface maintenance), and the mold surface is also the most critical. The product appearance and accuracy mainly depend on the mold surface, so the material and thickness of the coating on the mold surface become the key, and the mold surface cannot be reached, No matter how the molding process is adjusted, it is ng (I think everyone knows). If there is a bad appearance, generally first check whether there is foreign matter on the surface of the mold. If there is any, use willow to remove it. There is no special requirement on the surface of the mold. Generally, do not use a knife or other hard objects. The mold should avoid beating, falling, and avoid the sudden air failure of the equipment, short circuit and oxidation.

molding conditions:

molding is completed by 9 axes, There are three preheating shafts, two (or one) forming shafts and four (or three) cooling shafts. After the mold is guaranteed, the forming conditions determine the quality of the product. Generally, the poor surface of the lens is mainly produced between preheating and forming. If the preheating and forming temperature conditions are not properly matched (even one degree), the quality may be affected; Cooling 1 and 2 mainly determine the surface accuracy of the lens, because the glass shrinks through the cooling axis after softening. If the cooling temperature and pressure are not set properly, it will have a great impact on the surface accuracy of the lens

molding machine maintenance:

the molding room has always been a high-temperature environment, all metals will oxidize when encountering high temperature, and the mold has been circulating, so it will bring in foreign matters outside, so the maintenance of the molding room has become necessary. Maintenance frequency: if the maximum molding temperature is below 600 ℃, it can be maintained once in 1 ~ 1.5 months. If the maximum molding temperature is above 600, it is recommended that the maintenance cycle be shortened to once every 20 days. During maintenance, the molds on the equipment should be maintained together. In addition, it is also necessary to confirm the conditions of heating plates, screws and release rods in the molding room. (detailed formula (9) refer to the operation standard for the poor meshing method of the gear pair in the gearbox of the radial piston oil pump of the metal impact testing machine)

safety:

because the molding machine operates at high temperature, the chiller and equipment need regular spot inspection, the equipment alarm sound cannot be turned off, and the equipment cannot be climbed during operation, etc. The cooling water pipe joint of the equipment shall not be loose

workshop environment:

1000 level purification workshop, 100 level under the dust-proof operation platform, temperature 20 ℃ ~ 25 ℃, humidity: 45% ~ 70%

Li Yong Optical Engineer (end)