Jewelry casting also known as precision casting, its history is very long. Investment casting process has experienced two main development stages, was 1935 theCanadian Jungersen invented the elastic rubber model; two is in the middle of twentieth Century (1940~1950 years), the long-term use of dental casting method in the industry successfully used in jewelry production. Since then, casting jewelry grew in popularity, the technology has become the main method of modern jewelrymanufacturing technology, there are about 70% Au, Pt, Ag jewelry products usinginvestment casting technology. Some advanced countries and regions in the world,such as Italy, Germany, Japan and Hongkong, USA China, casting technology in-depth, comprehensive study on jewelry casting, casting equipment, in the production process, the original (DES) material has made significant progress in.
Jewelry casting involve many equipments, mainly by the wax injection equipment,powder equipment and casting machine.
A, wax injection device
Wax injection device mainly comprises a vacuum wax injection machine and pneumaticwax injection machine, using air pump pressure, make the wax liquid filling rubbermold cavity. Lost wax casting production is an important working procedure in the wax,the quality has an important impact on the jewelry products. The widespread use ofearly is a simple pneumatic wax injection machine, wax quality is relatively difficult to guarantee, especially fine wax to forming. In twentieth Century 80 years after thevacuum wax injection machine, injection wax before evacuating the rubber mold, thewax is in a vacuum state betting wax, the filling performance is optimized, therefore,can obtain relatively thin wax pattern, improve the filling ability of wax. 90 years after the development of vacuum wax injector higher degree of automation, such as digitalvacuum wax injection system produced by Yasui company in Japan, with two wax injection system to minimize the shrinkage of wax, wax injection parameter can be any combination of. The rubber mold into the mold clamping manipulator, input the program, press the "start" button, it can automatically complete the whole process.The device to control the temperature, wax injection effect is perfect.
Wax injection mold of previous to the rubber mold, has the certain thickness requirements. In recent years, the metal film on the part of the structure, making wax pattern is very thin, almost transparent, stability and the weight, size is very good,suitable for batch piece structure simple.
Two, open the powder equipment
Simple is easy to make slurry mixer is widely used in gas, the powder process to go through multi-channel processes, complex. 90 years after the vacuum automaticpowder stirring machine, it sets the mixers and vacuum sealing device in a body, can complete the whole process from stirring casting powder to filling forming under vacuum state, effectively reduce the bubble, the smoothness and better products.Vacuum powder stirring machine generally has a quantitative water and stirring timeand speed setting function, improve the degree of Automation Open powder, simple operation, time saving.
Three, baking furnace
Jewelry industry gypsum calcination furnace used mostly by resistance furnace, is generally three surface heating, uneven temperature distribution in the furnace,roasting time is not easy to adjust the furnace atmosphere. In order to achieveuniform distribution of wax residue and automation control, eliminate the target temperature furnace, in recent years the continuous development of some advancedroasting furnace. For example, Italy’s Schultheiss company developed a new type offurnace, heat resistant steel is arranged in the heating element and plaster, fan is installed on the roof, forced air flows through the heating element and returns from the bottom of furnace, which forced air flow in the furnace, improves the thermal insulation of the furnace shell can. Germany developed a roasting furnace more advanced, the hearth rotary mode, the plaster is heated evenly, smooth, fine plaster,particularly in the advanced wax casting process requirements. The furnace boxsurrounded by heating, there are double brick partition, temperature uniformity and stability, good insulation performance, after two times after the full combustion,exhaust gas is pollution-free, have a negative impact on the environment will not. At present, many countries in the production of such a roasting furnace.
Four, casting machine
Casting machine is very important jewelry in investment casting equipment, is to ensure that an important condition for the quality of the products. Because the jewelry products are fine, the liquid metal in the casting process can quickly solidified and the loss of liquidity, therefore, gravity casting routine to ensure its forming, we must introduce some external force, to promote its rapid filling cavity, in order to obtain theworkpiece shape integrity, a clear outline. According to the external form, commonly used for jewelry casting machine mainly centrifugal and static casting machine two.
(1) centrifugal casting machine: the liquid metal into the cavity using centrifugal force to produce high-speed rotation, the filling speed is fast, is conducive to forming, smallworkpieces with complex for Au, cast Ag alloy; for Pt, because it is in the liquid statetime is very short, with centrifugal casting is suitable for. At present, some small factories still use a mechanical drive type centrifuge is simple, it does not come withinduction heating device, using oxygen (Yi Que) melting metal, or the use of molten gold machine metal smelting, and then the metal liquid into the centrifugal castingcrucible, metallurgy quality is not guaranteed. The modern centrifugal casting machine have improved greatly in this respect, set induction heating and centrifugal pouring in one, suitable for casting Au, Ag, Cu alloy.
Compared with static casting, centrifugal casting pouring the liquid metal flow isserious, prone to the maximum amount of metal, metal liquid on stomatal cavity wallerosion, easily lead to severe cracking or peeling, mould of centrifugal casting defects such as relatively less. Aiming at these problems, improving driving technology andprogramming ability of modern centrifugal casting machine, a function mold centershaft and the rotary arm angle designed speed, from 90 degrees to 0 degrees,considering the centrifugal force and tangential inertial force so that the metal liquid flows into the crucible, cast role, helps balance the liquid metal, prevention of liquid metal first along the runner wall reverse rotation direction flow in the bottom of the casting mold; a pumping device, gas convenient cavity discharged smoothly, improvethe filling ability; at the same time with the temperature measuring device, can greatly reduce the artificial error of judgment.
(2) static casting machine: suction casting, pressure, vacuum, the metal liquid fillingcavity. Compared with the centrifugal casting, static casting machine is relatively smooth, scour the small metal liquid on the cavity wall; the maximum amount a castmetal. Therefore, the static casting machine has been more and more widely used injewelry manufacturing industry. Static casting machine has a variety of, the mostsimple is blister machine. The main components of the machine for vacuum system,without heating melting device, therefore, to be used in conjunction with the torch orfurnace, and has the advantages of simple operation, high efficiency. Because it iscast in the atmosphere, the liquid metal has two oxidation breathing problems, the whole casting process controlled by the operator, therefore, many influencing factors on the quality of the people.