Analysis And Solutions On Injection Molding Defects Of PEEK Thick-walled Tube

Injection molding products have become indispensable in our lives, but injection molding products that made of special engineering plastics almost are used on special occasions. There are all kinds of injection molding defects on the PEEK products during injection molding. This paper made a study about the thick-walled PEEK tube. The diameter of thick-walled tube is 218mm, outer diameter is 258mm. The height is 100mm. The thickness is up to 20mm beyond conventional products. There are many injection molding defects on the surface of products, such as obvious weld line, black spots, gate dark mark, cold slug, silver marks and porosities etc.By observing injection molding process of PEEK thick-walled pipe and simulating melt flow by using MOLDFLOW, this paper found the location of weld line. The accumulating air stops the integration of two melt flow, results in obvious weld lines. After improving mold venting, the weld line was improved significantly. By observing injection molding process of PEEK thick-walled pipe and simulating melt flow by using MOLDFLOW, this paper found that small mold runner,Φ10mm semicircle, and pits on the inner surface resulted in black spots. By increasing the size of the runner to Φ10mm U-shape and polishing its surface, the black spots disappeared. By adjusting the gate size and injection velocity, this paper found that the gate dark marks are connected with the injection velocity, not with the size of gate. At last, from the perspective of solving products injection defects, and taking account of reducing waste and preventing leak of hot oil, the mold of thick-walled tube was redesigned. Practice has proved that such a large thick-walled PEEK tube can be processed by injection molding satisfactorily.