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.
Plastic extrusion is used to create a
multitude of different products ranging from garbage bags to plastic
tubing. Extrusion comes in three different forms; direct, indirect and
hydrostatic which all have their pros and cons. The type of extrusion we
are studying is direct extrusion, also known as forward extrusion, and
is the most popular of the three forms of extrusion. It is the process
of moving material through a die of the desired shape of the
cross-section. An extruder works by melting down plastic pellets, called
resin, that are then forced down a barrel by a screw where they
continue to melt and are finally pushed out through a die that gives
them their final shape. The extrusion process can be continuous,
potentially producing any desired length of material, or semi continuous
to produce many pieces of material. The process may be hot or
cold.(Crawford, R., 1998)
1.2 Statement of the Problem
All over the globe, and in recent time
plastics have made a benchmark in virtually all areas of
industrialization. In Nigeria, the use of plastic both for domestic and
industrial purpose cannot be neglected. It is widely seen in our
environment that plastic waste constitutes largest percentage of waste
products. There is a need to design a cost effective plastic extruding
machine. Successful completion of this project will create new job
opportunities in Nigeria.
1.3 Aim of the project
The aim of the project is to design and
fabricate a cost effective plastic extruding machine used to produce a
hollow pipes for domestic and industrial purpose.
1.4 objectives of the project
The objectives of this project will include the following;
i. Design consideration of a low cost pipe extruding machine.
ii. CAD modeling of the proposed machine with solid works
iii. Fabrication and testing of the proposed extruder.
1.5 Methodology to be adopted
The methodologies to be used in this
project are classified into the three stages; firstly, literature review
of the existing design will be researched, followed by the design
calculations and CAD engineering models with Solidworks, then the final
stage which will be fabrication and testing. In the construction stage,
materials will be sort locally in Nigeria, material/weight reductions
will be put into consideration