Push-Pull Injection Molding

- Oct 16, 2018-

Such as injection molding process, this molding method can eliminate defects such as melt seams, voids, cracks and microscopic porosity in plastic parts, and can control the arrangement of reinforcing fibers. It adopts two main injection units and one double injection unit. Mold. In operation, the main injection unit pushes the melt overfilling the mold cavity through a bypass. The excess material enters the auxiliary injection unit through another gate, and the auxiliary injection screw retreats to receive excess melt in the cavity. Then, the auxiliary injection screw moves forward to inject the melt into the cavity, and the main injection unit receives the excess melt in the cavity.


The main and auxiliary injection units are repeatedly pushed and pulled to form a vibration shear flow of the melt in the cavity. When the melt near the mold wall solidifies, the melt of the core flows in vibration and shear, when approaching the melt near the mold wall. When curing, the melt of the core is oriented under the action of vibration shearing and gradually solidifies to form a product with high degree of orientation. Generally, the molding of the product requires about 10 cycles, up to 40 times.


The push-pull injection molding cycle is longer than the normal injection molding cycle, but since the material is cooled and solidified during the push-pull motion, the packing phase is not critical to controlling shrinkage and warpage. In the push-pull injection molding, the injection phase and the pressure holding phase are combined into one. The push-pull injection molding of glass fiber reinforced LCP by this injection process shows that the tensile strength and flexural modulus of the material can be increased by 420% and 270%, respectively, compared with conventional injection molding.