What is used for mass production of plastic parts by injecting heated plastic and extracting parts?

• A. Extrusion
• B. 3D Printing
• C. Injection Molding
• D. Casting

Answer: (C)

Injecting heated plastic into a mold and then ejecting the finished part is injection molding. In this process, plastic is melted, forced under pressure into a reusable mold cavity, cooled, and then the part is released. This setup is ideal for mass production because the same mold can produce countless identical parts with tight tolerances, and automation lets many parts be made quickly in a single production run. The other methods don’t fit the scenario: extrusion makes continuous shapes like pipes or sheets rather than discrete parts; 3D printing builds parts layer by layer and is slower for high-volume output; casting involves pouring liquid material into a mold and is typically slower and less efficient for large quantities.