How to improve the weather resistance of automotive parts through injection molds?

1, Material selection and improvement of weather resistance
The basis for raising the weather resistance of vehicle components is selecting plastic materials with outstanding resistance. For instance, polycarbonate (PC), acrylonitrile butadiene styrene copolymer (ABS), and their alloy materials (like PC/ABS), polyamide (PA), etc., these materials themselves have strong weather resistance and can sustain stable performance in outdoor situations for a long length. Further enhancing the weather resistance of the material by including particular additives are some modified polymers especially suited for weather resistance, including weather resistant ASA, weather resistant PMMA, etc.
Apart from choosing high-performance plastic materials, including weather resistant agents, antioxidants, UV absorbers, and other additives helps to enhance the weather resistance of materials. Antioxidants can slow down material aging and stop the chain reaction of materials during the oxidation process; UV absorbers can absorb UV radiation and convert it into benign thermal energy, so shielding materials from UV damage.
2, Influence of die structure design on weather resistance
rational channel design
Injection mold design heavily relies on flow channel design. Reasonable flow channel design helps to guarantee that the plastic melt consistently and firmly fills the mold chamber, thereby preventing shrinkage and bubbles. These flaws lower the components' weather resistance in addition to their look quality. To guarantee that the plastic melt can flow smoothly and fill the mold cavity, the size, form, and layout of the flow channel should thus be rather developed according to the form and size of the components in mold design.
Cooling system optimization
The cool effect of the mold and the forming quality of the components depend much on the design of the cooling system. A sensible cooling system design can help the mold to increase dimensional accuracy and stability, lower internal stress of components during the cooling process, and enable speedy and uniform cooling of the mold. Uniform cooling can, meantime, also lower stress concentration on component surfaces, hence enhancing their weather resistance. Consequently, in mold design, the architecture and number of cooling channels should be fairly planned depending on the form and size of the components to guarantee that the mold can cool rapidly and uniformly.
Exhaust system improvement
Injection molds use the exhaust system-a device for releasing volatile compounds and air from the mold chamber. A thorough exhaust system can guarantee that the air and volatile compounds in the plastic melt filling chamber may be released in a timely manner, therefore preventing flaws including bubbles and burning. These flaws lower the components' weather resistance in addition to their look quality. Thus, in mold design, the position, size, and quantity of exhaust slots should be reasonably constructed depending on the shape and size of the components to ensure that the exhaust system can operate without problems.
3, Optimization of molding process enhances weather resistance
Control of injecting molding temperature and pressure
Key elements influencing injection molding quality are temperature and pressure of injection molding. Inappropriate injection molding temperatures can cause plastic to break down, create corrosive fumes, damage the mold's surface, and also induce internal tension inside the components therefore lowering their weather resistance. Low injection molding temperature could provide poor plastic flowability, which makes it challenging to fill the mold cavity and causes flaws including inadequate component filling. Consequently, in the injection molding process, the injection temperature and pressure should be somewhat regulated depending on the properties of the chosen material and the shape and size of the components to guarantee that the plastic melt can uniformly and stably fill the mold cavity.
Modification of holding time and injection speed
Important elements influencing the quality of injection molding also are speed and holding times. Strong impact of plastic melt on the mold cavity caused by too fast injection speed might result in higher wear on the mold surface and internal tension in the components. In the cooling process of components, too long holding times can result in too great shrinkage stress, therefore reducing their dimensional accuracy. To thus ensure that the parts can be made properly and have minimal internal stress, the injection speed and holding time should be changed fairly depending on the properties of the chosen material and the shape and size of the components in the injection molding process.
Mold temperature control
Furthermore greatly influencing the quality of injection molding is the temperature of the mold. Strong fluidity in the plastic melt resulting from too high a mold temperature can induce flaws in the component including overflow and flash. When filling the mold cavity, a too low mold temperature would cause the flowability of the plastic melt to decrease, thereby complicating the filling process. To guarantee that the plastic melt can uniformly and stably fill the mold cavity and rapidly cool down for molding, the mold temperature should thus be reasonably controlled in the injection molding process depending on the properties of the chosen material and the shape and size of the components.
4, Enhancement of weather resistance by post-processing technology
Heat treatment
One useful approach to raise injection molded parts' performance is heat treatment. Heat treatment can remove residual tensions inside injection molded components, enhance their dimensional stability and weather resistance. Typical techniques of heat treatment consist in annealing, tempering, etc. Tempering treatment may rapidly cool the injection molded parts following heating, so improving their hardness and wear resistance; Annealing treatment can gradually cool the injection molded parts during the heating process, so removing internal tension. The material properties and use criteria of the injection molded parts will help one decide on a heat treatment technique.
Surface treatment
Another good approach to increase the weather resistance of injection molded products is surface treatment. Surface treatment helps to provide a protective film on injection molded items' surfaces that keeps them from being eroded by the surroundings. Among common surface treatments include spraying, electroplating, chemical plating, etc. Electroplating and chemical plating treatments can form a metal coating on the surface of injection molded parts, so improving their corrosion resistance and wear resistance; spray treatment can form a uniform coating on the surface of injection molded parts, so improving their weather resistance and aesthetics. The use environment and needs of the injection molded parts will help one decide on a surface treatment technique.