In the processing of plastic products, because of the high light transmittance of plastics, it is inevitable that the surface quality requirements of plastic products are severe, and there must be no markings, pores or whitening. Fog, black spots, discoloration, luster and other shortcomings, so the entire injection molding process for materials, equipment. Molds, and even the design of products, must pay great attention to and put forward strict and even special requirements. Secondly, because plastics have high melting point and poor fluidity, in order to ensure the surface quality of the products, the process parameters such as machine temperature, injection pressure and injection speed are often finely adjusted, so that the plastic can not be filled with the mold, and it will not Internal stress is generated to cause deformation and cracking of the product. Therefore, from the preparation of materials, the equipment and mold requirements, the injection molding process and the material handling of the products must be strictly operated. The analysis should be carried out from three aspects:
1. When the wall thickness of the plastic product is large, the surface surface cooling speed is faster than that of the central portion. Therefore, as the cooling progresses, the resin portion of the center portion is expanded toward the surface, so that the center portion is insufficiently filled. This condition is called a vacuum bubble.
The treatment method is as follows: According to the wall thickness, a reasonable gate and sprue scale are recognized. Generally, the height of the gate should be 50% to 60% of the wall thickness of the product; until the gate sealing is stopped, a certain amount of supplementary injection material is left; the injection timing should be slightly longer than the gate sealing time; the injection speed is lowered, and the injection pressure is advanced. Use a material with a high degree of melt viscosity.
Second, bubbles formed by the onset of volatile gases.
The treatment method is as follows: in the processing of plastic products, the pre-monotonic is sufficient, and the monotonous moisture content of the material after the monotonic detection is satisfactory for the injection molding requirement; the resin temperature is lowered to avoid the differentiation gas.
Third, the bubble formed by poor fluidity can be treated by advancing the temperature of the resin and the mold, and advancing the injection speed.