Introduction
Under the general trend of automotive lightweighting and environmental protection, ABS plastic has become the material of choice for manufacturing automotive plastic parts due to its excellent mechanical properties and ease of processing. In this paper, we will discuss in depth the key technologies and post-processing processes of ABS plastic injection molding to provide a professional technical guide for automotive manufacturers and plastic product makers.
- Drying treatment of ABS resins
ABS resin is extremely hygroscopic, with a moisture content of about 0.3% and a surface moisture content sometimes as high as 0.8%. Therefore, drying treatment must be carried out before molding to reduce the effect of moisture on product quality. Use a feeding device with a drying system, or a circulating air drying oven with a drying temperature control of 70 to 90°C for about 6 hours to obtain parts with a high gloss surface.
- Injection molding temperature control
The processing temperature of ABS should not exceed 250°C. The material tube temperature of the plunger injector is 180 to 230°C, the screw injector is 160 to 220°C, and the nozzle temperature is about 200°C. For different grades of resins, such as heat-resistant grades and plating grades, the processing temperatures can be a little higher; while flame-retardant grades, general-purpose grades, and impact-resistant grades should be a little lower.
- The influence of mold temperature on ABS molding
Increase the mold temperature is conducive to melt filling, improve the surface quality of the parts, reduce internal stress, enhance the performance of the coating, but will increase the shrinkage of the parts and extend the molding cycle. For complex shaped parts with high surface quality and performance requirements, it is recommended that the mold temperature be controlled at 60 to 70°C.
- Selection of injection pressure and speed
Injection pressure depends on part wall thickness, equipment type and resin grade. Higher injection pressure should be selected for thin-walled, long-process, small-door, heat-resistant or flame-retardant resin products. Also, too high a pressure may make the mold difficult to release or damaged. Maintain holding pressure at 60 to 70 MPa to minimize internal stresses. The injection speed affects the fluidity of the ABS melt; too slow may lead to surface defects, while too fast may lead to insufficient venting and surface quality problems.
- ABS plastic molding post-processing
Internal stresses are usually present in ABS parts, but stress cracking is uncommon. For parts with high performance requirements, it is recommended that they be treated in hot air at 70-80°C for 24 hours and then gradually cooled to room temperature. In addition, internal stresses are tested by immersing the part in glacial acetic acid; if cracking occurs within 5-15 seconds the internal stresses are high, if no cracking occurs within 2 minutes the internal stresses are low.
Conclusion
The key to the growing use of ABS plastic injection molding technology in the automotive industry is the precise control of molding conditions and post-treatment processes. By optimizing these parameters, manufacturers are able to produce ABS plastic parts with high dimensional stability and surface quality, meeting the demand for automotive lightweighting and performance enhancement.
In addition, there are ultrasonic welding and hot-plate welding for plastic parts.
