The common coating composition and preparation are mainly made up of a variety of raw and auxiliary materials. The coating of traditional sand mold is attached to the outer layer of the sand core, and the molten iron will be directly contacted with the outer layer of the coating. Therefore, the quality of the casting surface will be affected by the coating quality of the sand casting, the coating layer of the EPC is attached to the outer layer of the foam model, but the hot metal does not flow through the outer layer, and the foam is vaporized from the inside, so the quality of the coating layer will not cause the surface quality of the casting. The coating process mainly includes the following:

(1) dip coating method simple operation, high efficiency and uniform coating for small and medium-sized foam pattern.

(2) Brush method – generally used for small batch production, or large and medium-sized pattern.

(3) Spray Xu method – used when the pattern has thin wall and easily deformed area.

Considering the structure and output of the motor shell, the whole dip coating method is undoubtedly a more appropriate dip coating method. The foam shape and sand core and the injection system will be dipped after the assembly is finished.

After drying, the drying methods of foam are natural drying and artificial drying. Artificial drying is divided into hot air drying, drying drying and microwave drying. The humidity of artificial drying is maintained at 50-60 degrees Celsius, and the time is about 2.5 hours. The drying room is ventilated to reduce the humidity of the drying room and improve the drying effect of the foam. For the pattern that has been dried and ready for pouring, use the moisture tester to detect the moisture, and the pattern within 7% can be packed for pouring.