In mechanical products with relatively small load but light weight requirements, aluminum alloy gearbox is a good choice. The problems of poor internal and external quality and high cost of casting aluminum gear box are easy to occur when sand casting is used for production; The aluminum alloy gearbox produced by die-casting process has such problems as high probability of hole defects, high investment and operation costs of equipment and molds, and difficult to achieve economical mass production. Metal mold gravity casting (hard mold) is an ideal production method for aluminum gear box because of its good mechanical properties, dense structure, high precision and good economy.
Sand cores (ordinary molding sand, resin sand or others) are often used for metal mold castings of thin-walled boxes. This is because it is difficult to pull the core from the metal core, or the mold lifting angle is large, which does not meet the size requirements of the parts, or the parts and molds are easily strained; The cooling speed of aluminum liquid is fast, the mold filling is difficult, and the casting is insufficient; The casting is easy to crack; All metal mold cavity is easy to choke. Therefore, the application of all metal mold casting in thin-walled box or cavity castings is greatly limited.
Based on the theory of “shrinking pipe method” and “temperature equalization theory”, the casting process and metal mold design of the castings were studied by using the all metal mold casting technology with the gearbox box and cover as the objects, in order to provide a reference for the application of all metal mold casting technology in thin-walled box or cavity castings.
In the medium batch production of thin-walled aluminum alloy castings, the all metal mold casting process is a good method. The product quality is good, the shape and size are well controlled, the production cost is low, and the operation process is not complicated. The riser design theory of “shrinking pipe method” and the metal mold design theory of “homogenizing temperature method” are effective methods to develop and apply the all metal mold casting process.