DESIGN AND FABRICATION OF A COST EFFECTIVE PLASTIC EXTRUDING MACHINE. A RESEARCH PROJECT MATERIAL ON MECHANICAL ENGINEERING
CHAPTER 1
INTRODUCTION
1.1 Extrusion process
The extrusion process began in the 1800s by preheating the metal and forcing it through a die via a hand driven plunger known as squirting (Rauwendaal, C., 2001). Extrusion is now possible for metals, polymers, ceramics and concrete. Plastic extrusion began in the 1930s and the continuous process has been applied to manufacturing at high volume. Plastics have been very popular in the modern world because of its low cost and ease of manufacturing.
Plastic extrusion is a deformation process used to produce long, straight, semi-finished plastic product such as plate, solid and hollow sections, tubes and wires and strips. The principle is very simple: under a high load, a billet is squeezed under closed container through a die, to give a desired product. It is commonly used industrially to produce domestic and industrial products such as, chairs, pipes etc.(Michaeli, W., 2003)
Extrusion process may involve many stages through a single hole die or multiple hole die to obtain the final shape of a component. Dies of appropriate shape and sizes are then required to impart the right shape and specified tolerance in their respective passes. A welding chamber die (bridge, spider etc.) under hot condition is common for extrusion of hollow component. Square dies for single and multi-hole extrusion under hot condition have been widely used. Continuous dies such as streamlined, conical, elliptical, hyperbolic and cosine dies are becoming important for manufacture of better plastic product, in plastic extrusion, the required shape of the product is produced with a die.
Extrusion through multiple hole dies, using a high capacity extrusion press is preferred for reasons of economy and high productivity.
Completion of this project will give us a great deal of knowledge of experience in the engineering field, knowledge of the extrusion process and troubleshooting skills for the future.