How Plastic Injection Molded Parts are Made
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Plastic injection molding is a highly efficient manufacturing process used to produce parts by injecting molten plastic into a custom-designed metal mold. It is the most common method for mass-producing plastic parts, ranging from complex automotive components to simple household items like bottle caps. |
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How the Process Works The injection molding cycle is a repetitive process that typically takes between 15 and 120 seconds. 1. Clamping: The two halves of the metal mold are pressed together with enough force to keep them sealed against the high pressure of the incoming plastic. 2. Injection: Plastic granules (resin) are fed into a heated barrel, where they are melted and mixed by a rotating screw. Once the material is molten, the screw acts like a plunger to force the liquid plastic into the mold cavity. 4. Dwelling (Packing): The machine maintains pressure to ensure the plastic fills every corner of the mold and to compensate for shrinkage as the material begins to cool. 5. Cooling: The plastic solidifies inside the mold. Internal cooling lines (often filled with water) help speed up this process. 6. Mold Opening: Once the part is solid, the clamping unit opens the two halves of the mold. 7. Ejection: Ejector pins push the finished part out of the mold, and the cycle begins again. |
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Anatomy of the Mold The Mold: The "heart" of the process and is usually CNC machined from steel or aluminum. Cavity & Core: The "A-side" (cavity) usually creates the outer, cosmetic surface, while the "B-side" (core) creates the internal features. Sprue & Runners: These are the channels that lead the molten plastic from the machine's nozzle into the specific part cavities. Gate: The small opening where the plastic actually enters the part cavity. Draft: A slight taper on the walls of the part (usually 1-2 degrees) that allows it to slide out of the mold without getting stuck. |
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Common Materials & Applications Different plastics are chosen based on the required strength, flexibility, or heat resistance of the final product. ABS Tough, impact-resistant LEGO bricks, car dashboards, electronic housings Polypropylene (PP) Chemical resistant, flexible Food containers, medical syringes, living hinges Polycarbonate (PC) Transparent, very strong Safety goggles, bulletproof glass, lenses Nylon (PA) High wear resistance, strong Gears, bearings, zip ties Polyethylene (PE) Durable, moisture-proof Milk jugs, plastic bags, toys |
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Advantages of Plastic Injection Molding High Speed: Ideal for producing thousands or millions of identical parts. Low Waste: Excess plastic in the runners can often be reground and recycled. High Detail: The extreme pressure allows for very intricate shapes and textures. Low Labor Cost: The process is almost entirely automated.
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 Information for inventorsPre-Production Process1. You need to discuss your idea with a patent attorney; they can help you with the legal requirements of the patent office. Be very careful of sharing your new idea before those legal requirements are met. Our staff is always happy to assist and advise inventors with their inventions. 2.Peliton will sign a non-disclosure agreement, so you will feel comfortable knowing that your product or invention is protected. 3.Technical Drawings - Our company has the ability to produce technical drawings,(work load permitting) or refer you to someone in your area who can do them for you. 4.Prototype - Peliton will work with you to develop a prototype of your product. 5.We will then guide you through a complete cost analysis. The cost will be based on your 3-D drawings, the weight and volume of the part, your assembly requirements, the number of parts you need and the time frame of production. Remember, tooling drives production costs. A one-cavity mold only makes one part at a time, so you get fewer parts per hour than with a multi-cavity mold, but a one-cavity tool is cheaper. Lower the cost of your product by producing more cavities. It's a trade off between your tooling budget and your production budget. Peliton is a company committed to getting your custom molded products into production as quickly and economically as possible.
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