Which process uses a thermoplastic sheet formed by heating and drawing onto a mould with vacuum to yield shallow parts?

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

Answer: (A)

Vacuum forming is the process where a thermoplastic sheet is heated until soft and then clamped over a mold. A vacuum pulls the sheet against the mold surface, forming shallow, hollow shapes. After it cools, the part is trimmed from the sheet. This method is ideal for large, shallow parts with relatively uniform thickness, like trays or enclosures, because it uses a simple mold and provides smooth surface detail. It differs from blow moulding, which forms shapes by expanding a heated tube with air pressure inside a mold; extrusion, which pushes material through a die to make continuous profiles; and line bending, which locally heats along a line to bend a sheet without a full mold.