Due to the unique characteristics of the plastic parts […]
Due to the unique characteristics of the plastic parts of the complex parts of the automobile, the design of its injection molding needs to fully consider the following factors, the drying treatment of the material, the new requirements of the glass fiber reinforced material for the screw, the driving form and the mold clamping structure Wait.
First of all, when the commonly used resin materials such as automobile bumpers and instrument panels are modified resins such as modified PP and modified ABS, the resin materials have different hygroscopic properties to meet the requirements of moisture content during molding (generally required ≤0.2 %), the resin raw materials must be dried by hot air or dehumidified before entering the injection molding machine screw for pre-molding measurement.
Modified PP (PPEPDM) resin has low hygroscopicity. Generally, a hot air dryer can be used for 2-3 hours at 80-100°C. Modified ABS (PCABS) has strong hygroscopicity. Before forming and drying, use a dehumidifying dryer for dehumidifying and drying. We have fully considered the function and application of the dehumidifying and drying system in the design of the automotive complex plastic parts molding system.
Second, the current domestic automotive plastic parts are basically plastic products without glass fiber reinforcement. Compared with the resin containing chopped glass fiber reinforcement, the material and structure of the screw of the injection molding machine used to form the glass fiber-reinforced plastic parts are as follows: Big difference. When designing the injection molding machine, pay attention to the alloy material of the screw barrel and the special heat treatment process to ensure its corrosion resistance and strength.
Third, because auto parts are different from conventional products, their cavity surfaces are very complicated, with unequal forces and uneven stress distribution, so the machining capacity needed for them is the key consideration in the design. The processing capacity of the injection molding machine is embodied in two aspects: clamping force and injection capacity (expressed by the maximum theoretical injection volume). When the injection molding machine is forming a product, the clamping force must be greater than the opening force generated by the mold cavity pressure, otherwise the mold parting surface will separate and cause flash.