ZLYJ series speed reducer is a transmission part that possesses high precision hard gear surface and thrust block designed for plastic screw extruder. The design of product adapts all kinds of norm specified in ZBJ19009-88/ it features that gear and axis parts are made of high strength alloy steel. The gear is processes by carburization, quenching and tooth grinding process. The precision of gear is grade 6 specified in GB10095-88. The hardness of gear surface is HRC54~62. At front end of hollow input axis there is large specification thrust bearing that will bear axial thrust force while the screw is working. The complete machine features ,high in bearing capacity, stable in transmission, low noise, high efficiency, etc.