Rapid Plastics - Injection Molding's Basics
By Jon T Smith
Injection molding is a manufacturing technique for making parts from both thermoplastic and thermosetting plastic materials. Heated, fluid plastic is injected at high pressure into a mold, which is the opposite of the desired product shape. Injection molding is widely used for manufacturing a variety of parts, from the smallest component to entire body panels of car.The process of injection molding can be described in four simple steps. These include Plasticizing, Injection, Chilling, and Ejection. Each of these steps is different from the other and the right procedure is required for the successful completion of the total process.
These steps can be discussed as follows:
Plasticizing - It involves the conversion of the polymer material from its normal hard granular form at room temperatures, to the liquid which is necessary for injection at its correct melting temperature.
Injection - This is the stage during which this melt is introduced into a mold to completely fill a cavity or cavities.
Chilling - It is the act of removing heat from the melt to convert it from a liquid consistency back to its original rigid state.
Ejection - The ejection phase is the last phase where the removal of the cooled, molded part from the mold cavity is done.
Pelletized or powdered materials that are used in injection molding machines are mostly:
- Acrylonitrile-Butadiene-Styrene (ABS)
The use of these basic steps in sequence or as a cycle is the process of injection molding done to obtain or manufacture parts. Cycle time usually ranges from 10 to 100 seconds and are controlled by the cooling time of the melted plastic. The melted plastic comes from hard plastic pellets that are fed into the hopper of the injection-molding machine. The pellets or plastic powder is melted inside the machine and then forced into the mold through a nozzle by a long screw within a heated cylinder. It is the most common method of production, with some commonly made items including bottle caps and outdoor furniture. Injection molding typically is capable of tolerances.
Plastic molding applications are used in medical field like components for blood analyzer equipments, heart pump parts, orthopedic devices and custom knee braces. In automotive engineering it is used for mechanical levers, gears, gaskets and switches. It is also used for aerospace, automotive, avionics and computer components.
Rapid Prototyping - EMS USA provides rapid prototyping services, such as Stereolithography (SLA), rapid tooling, and rapid manufacturing.
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