What is the barrel and screw of an extruder?

Barrel: 

The barrel is a cylindrical housing through which the material being processed (such as plastic pellets or powder) is fed into the extruder. It provides a controlled environment for the material to be heated, melted, and transported through the extrusion process. Barrels are typically made of durable materials like steel or other alloys that can withstand high temperatures and pressures. They may also have heating elements along their length to melt the material more effectively.

Screw: 

The screw, also known as the extrusion screw or auger, is a rotating shaft housed within the barrel. Its primary function is to convey, compress, melt, and mix the material as it moves along the length of the barrel. The screw is typically designed with a helical flighting (grooves or threads) along its surface, which helps to move the material forward while also applying pressure to melt and homogenize it. The design of the screw can vary depending on the specific requirements of the extrusion process, such as the type of material being processed and the desired end product.