Which process uses air blown into an extruded tube with moulds on either side closing to form hollow products?

• A. Blow moulding
• B. Vacuum forming
• C. Compression moulding
• D. Line bending

Answer: (A)

This question is about how hollow plastic parts are made using air pressure inside an extruded tube. In extrusion blow molding, melted plastic is formed into an elongated tube called a parison. The mold halves close around this tube, trapping the parison inside. Air is then blown into the tube, expanding the molten plastic outward so it takes the shape of the mold cavity. As the film of plastic cools, it solidifies into a hollow part like a bottle or container. This description—an extruded tube expanded by air inside closed molds on both sides—fits blow molding exactly.

That’s different from vacuum forming, which uses a heated sheet pulled into a mold by vacuum; compression molding, which involves placing preheated material into a mold and pressing it to shape (no extruded tube or internal air); and line bending, which bends sheet stock along edges to form shapes, not hollow objects formed by blowing air.