ABSTRACT
Mechanical engineering laboratory of Federal University of Minna, Nigeria requires extrusion machine that can be used for teaching and learning of PVC extrusion process. The teaching and learning of PVC extrusion are rarely thought using extrusion machines that help to bridge the gap between engineering graduate in industry and student learning in the university. Against this background, a need emerges for the design, and fabrication of laboratory PVC extrusion machine. The laboratory PVC extrusion machine is a machine that could be used to produce thermoplastics pipes. The PVC pipe is done by forcing the resin (PVC melt) to flow through an opening annular die. It is necessary to produce the pipe with indigenous technology to meet increasing demands of pipe usage in our homes such as, portable water sewage and electrical conduit pipes. The design of extrusion machine involves selection of specified drives, feeding and control systems. The drives used were spur gears, screw shaft, thrust bearing and electric motor. The required power for the machine was 6.93 kW with power scale up factor of 0.122 and gearing ratio of 2:1. The feeding system is cylindrical barrel of diameter 770mm and hopper with electrical control switch for control purpose. The machine is designed analytically and modelled using Pro- Engineer software before being fabricated. The compression ratio used for the design of the machine was 8:1 with extruder length being 1120 mm. The maximum shear stress for the extruder design was 17.1 k�/m2 with extrusion pressure of 7.7 � �/m2. The design extruder circumference speed was 1.2 �/� with plastic flow rate of 1m/s. The velocity drop at die inlet was 0.1 . Drag or volumetric flow rate of the PVC melt from the extruder was 0.0009 m3/s.The mass flow rate of the PVC melt was 7.9kg/s. The pipe produced by the machine is 40mm diameter. The pipe was bent in structure due to lack of automated temperature controller system in the machine and a plate to slide on to avoid deformation due to its weight. The machine efficiency is 51% and it was fabricated with locally sourced materials. The use of this machine for practising PVC extrusion process will boost student’s knowledge of extruding process.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Historical Background of the Study
According to Crawford (2000), manufacturing methods basically involve operations such as cutting, forging and casting. As time progressed, less readily available natural materials, such as ores, are converted into metals and also pass through a secondary mechanical working stage to be turned into something good and useful for mankind. The method chosen for a particular application will depend on many factors on the material being formed, the shape of the end-product, the market size, etc. And the methods available are continually increasing in number as new types of market demands mean that new manufacturing methods have to be developed to meet special needs (Crawford, 2000). Many of these new methods are hybrids of existing methods and they enable new shapes to be created with unique functionality or more attractive economics, therefore extrusion is one of the manufacturing methods called forming that does base on this fact.
Natural polymers have been with human beings since the beginning of time and began to be chemically modified during the 1800s to produce a number of materials. The manufacture of synthetic polymers has started since the early twentieth century. During World War II, the polymer industry has continued to grow increasingly and since then it has evolved into one of the fastest growing industries in the world. For the year 2000, nearly 200 million tons of synthetic polymeric materials, or plastics, were produced throughout the world to satisfy the ever increasing market demands (Griskey, 1995 and Carraher, 2003). Compared to other materials, polymers have plenty of advantages such as light weight, corrosion-resistance, and ease of manufacture. Plastic materials can be classified into two general classes, thermosets and thermoplastics. Unlike thermosets which cannot be reprocessed once the product is formed, thermoplastics can be reprocessed many times through certain approaches. Thermoplastics occupy more than 80% of the commercial polymer products in the world due to its advantage of being re-processable (Throne, 2004). Likewise, polyvinyl chloride (PVC) pipes a thermoplastic type of plastic have been considered as the ideal candidates for fulfilling the increasing market needs.
1.2 Statement of the Study
Presently in mechanical engineering laboratory of Federal University of Minna, Nigeria there is no extrusion machine that can be used for practicing extrusion process. Therefore, there is a need to understand the theoretical aspect of manufacturing process of PVC pipe forming by practical procedure. Teaching and learning of manufacturing process such as PVC extrusion will be effective if they are well supported with practical. The teaching and learning of PVC extrusion are rarely thought using machines that bridge the gap between working in industry and learning in the university. Against this background a need emerges for the design, and fabrication of laboratory PVC extrusion machine using locally sourced material.
1.3 Justification and Significance of the Study
Extrusion is a metal forming process that is employed in thermoplastic forming of pipes, tubes, wires etc. This process forces metal or plastic to flow through a shaped opening die under pressure (Dhar, 2005). The material is plastically deformed under compression in the die cavity. The process can be carried out hot or cold depending on ductility of the material. The tooling cost and setup is expensive for the extrusion process, but the actual manufactured part cost is inexpensive when producing significant quantities of extrusion products. Various materials can be extruded by this process and they are aluminium, copper, steel, magnesium, and plastics but aluminium, copper and plastics are most suitable for extrusion. This study is based on plastic extrusion of pipes.
Plastics are so widely used today, because it is almost inevitable due to its relatively low cost or their lightness or their ready availability in many colours. These are important factors; there are few applications where they would be sufficient justification for using plastics. For instance, in the automotive industry, where weight saving is a commendable objective to save energy. Plastics can be mechanically formed into complex shapes at very high speed at relatively low temperatures. This means that manufacturing costs are low, which is key requirement in any successful business. Thus the contributions to energy savings are more likely to come from the lower fuel bill at the manufacturing stage than at the end-user stage. The additional attributes of lightness, colour fastness, flexibility, chemical resistance, electrical insulation and so on, are bonus factors that are to be welcomed and can be put to good use in specific applications of plastics.
The driving force in any production environment is the tight control of the manufacturing process. To gain such control, the design, industrial, production and material engineering departments must generate effective process plans to manufacture products like thermoplastics and also to have worked on the formal design of the product. Production engineering need to be involved in product design cycle of polyvinyl chloride (PVC) pipe which could be available for home and industrial use. Extrusion is useful to produce PVC pipe in mass production in industry for instance the use of automated extrusion machine in Imurat International Ltd, Minna has helped producing thousands of quality PVC pipes per week. Therefore carrying out a research on production of PVC pipe would help in linking classroom understanding nature of extruding/forming process of thermoplastic to the industrial design application of the thermoplastics extrusion. The study undergoes process planning and design of PVC pipe within our environment. The pipe produced could be used to pass sewage and also to collect rain water in our homes.
1.4 Aim and Objectives of the Study
The study aims to design and develop a laboratory model of thermoplastic extrusion machine that can be used to demonstrate extrusion process to the student. The machine can also be used by practising technologist in the school of engineering workshop.
The objectives of this thesis are to:
i. design of polyvinyl chloride pipe laboratory extrusion machine
ii. fabricating of polyvinyl chloride pipe laboratory extrusion machine
1.5 Scope of the Study
This study covers the process planning and design of mono-extrusion die for thermoplastic or PVC pipe production. The study uses basic design specification for gear and shaft for power transmission. In the study, the die is designed based on annular cross section approach which serves as outlet for producing the PVC pipe. The study uses forward extrusion approach; hence Pro-Engineer is used for 3-Dimessional modelling of the laboratory extrusion machine. Failure analysis of the shaft is also carried out. Therefore, the laboratory extrusion machine is designed and fabricated for mechanical engineering student as a means of carrying-out workshop practise.
This material content is developed to serve as a GUIDE for students to conduct academic research
DESIGN AND FABRICATION OF POLYVINYL CHLORIDE PIPE LABORATORY EXTRUSION MACHINE
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