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What are the key points for injection molding of auto […]
What are the key points for injection molding of automotive plastic injection parts? Then follow our website to find out more.
First, 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 hygroscopically to meet the moisture content requirements during molding (general requirements ≤ 0.2) %), the resin raw material must be subjected to hot air drying or dehumidifying drying before entering the pre-plastic metering of the injection molding machine.
The modified PP (PPEPDM) resin has low hygroscopically and is generally used in a hot air dryer at 80-100 ° C for 2-3 h. The modified ABS (PCABS) has strong hygroscopically and is subjected to dehumidifying and drying treatment using a dehumidifying dryer before molding drying. We have fully considered the function of the dehumidification drying system in the design of automotive complex plastic parts forming systems.
Second, at present, domestic plastic parts for vehicles are glass-reinforced plastic products. Compared with the resin containing chopped glass fiber reinforced plastics, the material and structure of the screw for injection molding machine without glass fiber reinforced plastic parts are the Larger difference. When designing the injection molding machine, attention should be paid to the alloy material of the screw barrel and the special heat treatment process to ensure its corrosion resistance and strength.
Third, because the auto parts is different from conventional products, its cavity surface is very complicated, the force is not equal, and the stress distribution is uneven. The design processing power is considered in the design. The processing capability of the injection molding machine is reflected on both the clamping force and the injection molding capacity (expressed in the theoretical injection volume). When the injection molding machine is molding a product, the clamping force must be greater than the mold opening force generated by the mold cavity pressure, otherwise, the mold parting surface will be separated to produce a flash.
The formula for determining the mold clamping force of the injection molding machine is as follows: P mold clamping ≥ P cavity × F / 100. In the formula: P mold clamping is the clamping force (or clamping force) KN of the injection molding machine; P cavity is the average pressure of the cavity, MPa, related to the shape and shape of the product, the precision requirement and the number of cavities per model, etc. The range is generally between 25-40 MPa; F is the mold cavity and the horizontal overlap projection area CM3 of the runner and the feed port.
To ensure reliable mold clamping, the process clamping force during injection molding must be less than the rated clamping force of the injection molding machine. The theoretical injection volume of the injection molding machine is matched with the clamping force of the injection molding machine. It is the injection capacity of the injection molding machine with the polystyrene (PS) as the reference resin before leaving the factory.