Silver thread is mainly caused by the hygroscopicity of the material. Therefore, it should be dried under the condition of 10~15oC lower than the thermal deformation temperature of the resin. For the PMMA tree wax series with higher requirements, it needs to be dried for 4~6h under the condition of about 75t). In particular, when using the automatic drying hopper, it is necessary to select a reasonable capacity according to the molding cycle (molding volume) and drying time. It is also necessary to turn on the machine for drying several hours before the injection. In addition, too long stagnation time of material in the silo will also produce silver lines. When different kinds of materials are mixed, such as polystyrene. It should not be mixed with ABS resin, AS resin, polypropylene and polystyrene.