Extrusion moulding is described as...

• A. A mould is created from wood or epoxy resin
• B. A screw thread turns forcing the plastic material through a heater melting it, then acts as a ram and forces the plastic through a profile shape piece, the plastic solidifies and is moved along the conveyor belt
• C. A sheet of plastic is heated until it becomes soft and placed over the mould
• D. A tube of molten plastic is extruded between two halves of a mould

Answer: (B)

In extrusion moulding, plastic is melted and then forced to flow through a profile-shaped opening (a die) to form a continuous cross-section. The screw in the extruder both feeds and melts the plastic and pushes it through the die. As it exits, the material cools and hardens while being drawn away along a haul-off or conveyor, producing long shapes like profiles, pipes, or channels. This description matches extrusion most closely because it centers on melting, conveying through a profile die, and continuous movement away from the die.

The other descriptions refer to different processes: making a mould from wood or epoxy resin is about creating a mould rather than shaping material through a die; heating a sheet and draping it over a mould describes thermoforming; and extruding a tube between two halves of a mould resembles injection or blow moulding, not the continuous profile extrusion process.