At present, the production of motor shell is mostly sand casting, which has low production efficiency, high labor intensity and poor environmental conditions. However, EPC is a kind of advanced environmental protection special casting method, which uses dry sand without drilling binder and vacuum technology.



Lost foam casting is made of foam plastic and similar to the size of the casting structure. After dipping, the refractory coating is dried and embedded into the special sand box dry sand molding. The molten metal is poured into the molten metal, and the foam mold is burnt out and burned away. The metal liquid takes the place of the original foam plastic mold and occupies the space position. After cooling and solidification, the required casting is obtained. The lost foam casting process has many advantages, such as high precision of casting size, low surface roughness, less machining allowance, high utilization rate of liquid metal, less environmental pollution, complex shape castings, no need to take mold, and easy to standardize the production process.



The lost foam casting process is divided into three parts: white zone, yellow zone and black zone. White area is the production process of white foam mold, that is, pre foaming, foaming molding to the appearance of bonding. The yellow area is the coating preparation, painting and drying; the black area is the process of putting the pattern into the sand box, packing and filling sand, metal smelting, negative pressure casting, casting sand dropping and cleaning.



1. Selection of pattern material

At present, the widely used pattern materials are mainly EPS material (polystyrene foam), EPMMA material (poly methyl acrylic acid cool foam) and STMMA material (polystyrene methacrylic acid acetate copolymer tree vinegar foam plastic) three kinds. The characteristics of the three materials are as follows:

1) EPS material: cheap, carbon content up to 92%, less gas production, more residue after combustion.

2) EPMMA material: the dimensional stability and resilience of the pattern are better than EPS material, and the carbon content is low, but the gas evolution is large, it is easy to produce reverse spray during pouring, and the price is expensive.

3) Stmma material: a copolymer of EPS and EPMMA, with a carbon content of 62. It has both the properties of EPS and EPMMA. It overcomes the problem of carbon addition of EPS and EPMMA, and solves the problem of large gas evolution of EPMMA.

Due to the thin wall thickness of the motor shell, especially at the end of the heat sink, only 0.3 mm. In order to avoid slag inclusion defects in the casting, it is recommended to select the stmma copolymer with a density of 15-18.



2. Pre foaming and foaming

1) Pre foaming

The steam type pre starter is adopted, and the process is as follows: preheating feeding pre foaming drying curing.

2) Foam forming

Foam forming is the injection of mature foam particles into the cavity of the metal mold, forming a dense foam mold with small roughness. The technological process is as follows: closing die preheating feeding foaming forming cooling demoulding.

3) Pattern bonding and assembly

The pattern bonding and assembly is to bond the casting mold and gating system together to form a mold cluster in strict accordance with the requirements of the drawing size. It is an important process of lost foam casting. In order to obtain the lost foam castings, during the pouring process, not only the foam pattern is completely vaporized, but also the residue is not left. Similarly, the binder used for the mould assembly is fast gasification without residue. Similarly, the less the amount of binder, the better.



The methods of pattern bonding and assembly include cold glue bonding, hot melt adhesive bonding and fusion welding bonding. The lost foam hot melt adhesive has been commercialized and widely used in the bonding of pattern and gating and riser system in mass production. The hot melt adhesive has high solidification speed, high bond strength and good gap filling performance. Both thin-walled and thick wall patterns can seal the joint surface, which can meet the requirements of mass production.



Zhejiang Taixing Electromechanical Technology Co., Ltd. has been focusing on the R & D, production and sales of motor shell, aluminum motor shell, vertical motor shell, horizontal motor shell, aluminum die-casting motor shell, aluminum stretching motor shell, with complete categories, quality and quantity, which is trustworthy, welcome to inquire.