Injection Molding Process Steps: How Are Plastic Parts Produced?

1672906437 Injection Molding Process Steps

Successful custom injection molding requires process management that\’s guided by ability and precision timing. Tool and process engineers are front-and-center in the product and tool design phases, making decisions and guiding the steps necessary to ensure consistent and repeatable manufacturability of defect-free injection molded parts.

The upfront investment of time and knowledge by the joint team of engineers from the injection molded and OEM is crucial in informing the injection molding process, wherein the product and tool designs are brought together with project-specific resins. Breaking down injection molding step by step illustrates how all phases work together in an injection molding cycle to achieve successful outcomes.

1672906483 injection Molding Process02

  1. The tool closes, signifying the start of the injection molding cycle. Resin pellets are fed from a hopper into the barrel.
  2. The screw rotates to auger the pellets forward toward the tool. The resulting friction plus barrel heaters cause the pellets to melt. The screw is pushed forward and injects the material at the force and speed necessary to properly fill the tool cavity. During this step, it is imperative that displaced air escape through the vents and parting line designed into the tool for this purpose. Miscalculation or malfunction of these air release points could introduce defects and waste.
  3. After the tool cavity is filled, the resin must be allowed to cool. Water is cycled through the tool to keep a consistent temperature while the material hardens. Cooling times vary based on the plastic used and part thickness.
  4. While the injection-molded plastic part is cooling within the tool, the screw retracts and reloads with melt in preparation for the next injection. Heaters within the barrel screw keep the melt plasticized at its designated temperature.
  5. Once the molded material reaches its ideal ejection temperature, the tool opens, and the part is pushed out by the forward motion of the ejector rod and pins. The part can be extracted by a robot, manual operator, or falls freely into a bin underneath the tool.
  6. Sometimes, the molded parts have pieces attached called runners. Runners are simply extraneous material that gathers in the channels that the melt takes on its way to filling the tool cavity. Runners are either manually or robotically detached from the usable part, and usually ground and recycled to reduce costs and protect the environment. The injection-molded plastic parts are ready for inspection, packaging, and shipment.

Dongguan V1 Mold Technology CO., LTD. Is a wholly-owned subsidiary of the V1 group, which was founded in 2006. is an ISO, IAF, and IATF compliant company with over 15 years of experience in the design, production, processing, and manufacturing of plastic injection molds. We are committed to supplying our customers with robust automotive, medical, domestic appliances, electronics, commercial lighting, packaging injection molding products, and reliable services through our international commercial and production network.


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