Injection Molding Technology
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Conventional injection molding is the most widely used process for making plastics products. In that process heat and work- softened thermoplastic molding compounds are forced into a mold, where they are hardened by cooling. The original machines used a plunger and heaters to soften and move the molten compound to the mold (Figure 8.1 is a schematic diagram of such a machine). Modern injection machines use an extrusion type screw to mechanically heat and plasticize the compound and then inject the material into the mold. Those units are called reciprocating screw machines. Molding pressures of 5,000 psi commonly are used in reciprocating screw machines, and the mold must be able to withstand that force applied over the projected area of the part. Figure 8.2 is a schematic diagram of a reciprocating screw machine showing the several positions of the screw.
KeywordsFlexural Strength Impact Strength Injection Molding Injection Mold Flexural Modulus
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