backward due to the pressure from the fusion of plastics by the head of screw, so that the plasticated fusant can be stored at the top of the charging barrel for use during injection. The backward stroke of screw is determined by the quantity of materials injected as required by each molding of plastic parts 2)Injection When the screw stops rotating and moves backward, the mold clamping part begins to work to close the mold and the injection unit subsequently moves forward to make the nozzle and mold spruing gate joint with each other; the injection oil tank plunger drives the screw to move forward rapidly, and the injection pressure and speed as required by the molding technics inject the fused plastics into mold cavity. To avoid refluence of the materials injected into the mold and to supplement the small amount of materials needed due to the contraction caused by the cooling and molding of parts, the screw,upon completion of injection, shall still keep certain pressure on the fused materials, i.e. pressure maintaining until the materials at the gate have cooled and molded 3)Molding The fused materials in the mold cavity restore from viscous and fluid state to glassy state after being cooled. After complete cooling and molding, the plastic parts in the mold cavity are ejected by the ejector unit during mold opening, thereby the whole process of molding of the injected parts being Barrel Rotating screw Hydraulic motor Single check valve Closing mold 油压马达注q Injection cylinder Injection nozzle Heate Screw going ahead Pressure maintaining 冷却(可型化测量) Cooling(Plastication measure) 螺杆转 Screw backing off Demolding Screw rotating Fig 6-3: injection molding As indicated in Fig. 6-3, centering on the screw, three procedures shall be needed to complete an injection cycling period 1)The injection tank plunger, under the scheduled pressure, pushes the screw forward to inject the 2)The injection tank plunger, under the scheduled pressure, further pushes the screw forward to supplement the materials and to maintain pressure 3)The oil pressure motor drives the screw to rotate and to supplement materials to be plasticatedbackward due to the pressure from the fusion of plastics by the head of screw, so that the plasticated fusant can be stored at the top of the charging barrel for use during injection. The backward stroke of screw is determined by the quantity of materials injected as required by each molding of plastic parts. 2) Injection When the screw stops rotating and moves backward, the mold clamping part begins to work to close the mold and the injection unit subsequently moves forward to make the nozzle and mold spruing gate joint with each other; the injection oil tank plunger drives the screw to move forward rapidly, and the injection pressure and speed as required by the molding technics inject the fused plastics into mold cavity. To avoid refluence of the materials injected into the mold and to supplement the small amount of materials needed due to the contraction caused by the cooling and molding of parts, the screw, upon completion of injection, shall still keep certain pressure on the fused materials, i.e. pressure maintaining, until the materials at the gate have cooled and molded. 3) Molding The fused materials in the mold cavity restore from viscous and fluid state to glassy state after being cooled. After complete cooling and molding, the plastic parts in the mold cavity are ejected by the ejector unit during mold opening, thereby the whole process of molding of the injected parts being completed. Fig.6-3: injection molding machine operation process As indicated in Fig.6-3, centering on the screw, three procedures shall be needed to complete an injection cycling period: 1) The injection tank plunger, under the scheduled pressure, pushes the screw forward to inject the plasticated fused materials; 2) The injection tank plunger, under the scheduled pressure, further pushes the screw forward to supplement the materials and to maintain pressure; 3) The oil pressure motor drives the screw to rotate and to supplement materials to be plasticated; Rotating screw Hopper Hydraulic motor Injection cylinder Heater Barrel Single check valve Injection nozzle Injection Pressure maintaining Cooling(Plastication measure) Screw backing off Screw rotating Screw going ahead Demolding Closing mold