{"id":3681,"date":"2021-05-17T18:31:00","date_gmt":"2021-05-17T23:31:00","guid":{"rendered":"https:\/\/sybridge.com\/?p=3681"},"modified":"2023-10-16T12:17:04","modified_gmt":"2023-10-16T17:17:04","slug":"cosmetic-injection-molding-defects","status":"publish","type":"post","link":"https:\/\/sybridge.com\/cosmetic-injection-molding-defects\/","title":{"rendered":"Tips for Cosmetic Injection Molding Defects"},"content":{"rendered":"\n

Originally published on fastradius.com on May 17, 2021<\/em><\/p>\n\n\n\n

Injection molding is a simple manufacturing process used to rapidly and consistently produce parts in unique shapes. The process of\u00a0plastic injection molding<\/a>\u00a0begins with heating up\u00a0thermoplastic<\/a>\u00a0pellets. This molten material is then injected into a hardened steel mold through a pressurized nozzle. Once the part is cooled, it is ejected and the process is repeated.\u00a0Injection molding<\/a>\u00a0is one of the most popular manufacturing methods for plastic parts and engineers often use injection molding for high-volume production runs, as this process creates consistent parts quickly while often\u00a0decreasing costs\u00a0per part.<\/p>\n\n\n\n

While manufacturing plastic components with injection molding, some parts might come out looking and feeling better than others. However, that doesn\u2019t mean you\u2019re stuck with an inferior product. Here are seven cosmetic defects that can occur in plastic injection molding, plus their causes and potential solutions.<\/p>\n\n\n\n

\"Defects
Defects that occur in plastic injection molding can negatively affect aesthetic appeal and consistency part-to-part.<\/em><\/figcaption><\/figure>\n\n\n\n

Drag lines<\/h2>\n\n\n\n

Drag lines, also known as scrape lines, occur when there is not enough\u00a0draft\u00a0incorporated into the design of the vertical walls of a part. Vertical walls are the surfaces parallel to the direction of the mold. When there is not enough space for parts to eject properly, the vertical walls scrape against the mold and create unsightly lines.<\/p>\n\n\n\n

To best avoid drag, vertical walls should have a draft angle ranging from 1 to 2 degrees. Heavily textured surfaces can require draft angles of 5 degrees or more to prevent drag.<\/p>\n\n\n\n

Flash<\/h2>\n\n\n\n

Flash, also known as \u201cspew,\u201d occurs when molding material flows outside its intended chambers and protrudes over a part\u2019s edge. Flash is usually caused by a worn-down or poorly-designed mold, as well as excessively high injection pressure or mold temperature. Unlike a parting line, which shows the seams on an injection molded part, flash is a quite noticeable and unsightly defect.<\/p>\n\n\n\n

You can fix a one-time flash occurrence by simply trimming the excess material, but this isn\u2019t recommended for repeat flash occurrences. If you experience flash often when manufacturing plastic parts with injection molding, you should:<\/p>\n\n\n\n