Nail Making Machine

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FINAL YEAR PROJECT REPORT

UNIVERSITY OF NAIROBI DEPARTMENT OF MECHANICAL AND MANUFACTURING ENGINEERING PROJECT NO. JMO/01/2012

PROJECT REPORT TITLE: DESIGN OF A NAIL MAKING MACHINE SUITABLE FOR THE LOCAL COTTAGE INDUSTRY

This project report is submitted in partial fulfillment of the requirement for the award of the degree of Bachelor of Science in Mechanical Engineering.

Submitted by: FELIX ARINGO OLALA

F18/1873/2007

NGAO THOMAS KATIKU

F18/1860/2007

Project supervisor: DR. J. M. OGOLA May 2012

DECLARATION The content of this document is the original work based on our own research and to the best of our knowledge it has not been presented elsewhere for academic purposes.

FELIX ARINGO OLALA

F18/1873/2007

Signed………………………………….

Date: ……………………………

NGAO THOMAS KATIKU

F18/1860/2007

Signed…………………………………...

Date: ………………………………

This project is submitted as part of the Examiners Board requirement for the award of the degree of Bachelor of Science in Mechanical and Manufacturing Engineering from the University of Nairobi.

Project supervisor: DR. J. M. OGOLA Signed ………………………………….

Date: ……………………………….

i

DEDICATION This project is dedicated to our parents for their love and support during our studies.

ii

ACKNOWLEDGEMENTS We wish to express our sincere gratitude to our project supervisor, Dr. J. M. Ogola for his insight and guidance throughout the undertaking of this project. Our gratitude also goes to Eng. Michael Thubi of Numerical Machining Complex for his constant support while developing the Autodesk Inventor drawings and simulations. We are further grateful to Prof. Oduori, for the support he gave us and the Department of Mechanical & Manufacturing Engineering for providing the working environment and the Autodesk Inventor software at the laboratory for our use. Finally, we thank God Almighty for giving us the strength, good health and the opportunity to undertake this project.

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TABLE OF CONTENTS

DECLARATION ......................................................................................................................... i DEDICATION ............................................................................................................................ ii ACKNOWLEDGEMENTS ....................................................................................................... iii TABLE OF CONTENTS ........................................................................................................... iv LIST OF TABLES .................................................................................................................... vii LIST OF FIGURES .................................................................................................................. viii ABSTRACT ............................................................................................................................... ix CHAPTER 1: INTRODUCTION ............................................................................................ 1 1.1.

NAILS, NAIL MAKING AND NAIL MAKING MACHINE ........................................ 1

1.1.1.

Nails .......................................................................................................................... 1

1.1.2.

Nail Making .............................................................................................................. 1

1.1.3.

Nail Making Machine ............................................................................................... 1

1.2. PROBLEM STATEMENT .................................................................................................. 2 1.3. STUDY OBJECTIVE .......................................................................................................... 3 CHAPTER 2: LITERATURE REVIEW ................................................................................. 4 2.1

Definition ......................................................................................................................... 4

2.2

Background ...................................................................................................................... 4

2.3 Applications of nails.............................................................................................................. 5 2.4 Classification of nails ............................................................................................................ 5 2.5 Design.................................................................................................................................... 6 2.6 Raw Materials ....................................................................................................................... 7 2.7 The Manufacturing process ................................................................................................... 7 2.8 The Future ............................................................................................................................. 8 iv

CHAPTER 3: METHODOLOGY ........................................................................................... 9 3.1. A Survey of Nail Making Machines Currently Being Used In the Cottage Industry ........ 10 3.1.1.

Current Nail Making Machine Designs .................................................................. 10

3.1.2.

Perfect Automatic Wire Nail making machine ....................................................... 11

3.1.3.

Nail making machine – USA .................................................................................. 12

3.1.4.

N6-E Nail Making Machine.................................................................................... 13

CHAPTER 4: DESIGN OF NAIL MAKING MACHINE.................................................... 15 4.1.

SELECTION OF MATERIALS .................................................................................... 15

4.1.1.

Head Punch and Cutting materials .......................................................................... 16

4.1.2.

Crankshaft Material ................................................................................................ 16

4.1.3.

Fastener Materials ................................................................................................... 17

4.1.4.

Pulley Material ........................................................................................................ 18

4.1.5.

Bearing Material ..................................................................................................... 18

4.1.6.

Die block Material .................................................................................................. 19

4.1.7.

Flywheel Material ................................................................................................... 19

4.1.8.

Nail collector material............................................................................................. 19

4.2.

SELECTION OF MANUFACTURING METHODS FOR PARTS ............................. 20

4.3.

DESCRIPTION OF PARTS OF DESIGNED NAIL MAKING MACHINE................ 21

4.3.1.

POWER/DRIVING SYSTEM ................................................................................ 21

4.3.2.

WIRE FEEDING SYSTEM ................................................................................... 29

4.3.3.

NAIL HEAD FORMING SYSTEM....................................................................... 31

4.3.4.

NAIL CUTTING SYSTEM .................................................................................... 34

4.3.5.

MACHINE FIXTURE SYSTEM ........................................................................... 39

4.3.6.

NAIL EXIT SYSTEM ............................................................................................ 39

4.4.

WORKING PRINCIPLE OF INNOVATION ............................................................... 40 v

CHAPTER 5: DETERMINATION OF TECHNICAL AND ECONOMIC VIABILITY .... 43 5.1. TECHNICAL VIABILITY OF NAIL MAKING MACHINE .......................................... 43 5.1.1.

Performance ............................................................................................................ 43

5.1.2.

Environment ............................................................................................................ 43

5.1.3.

Maintenance ............................................................................................................ 44

5.1.4.

Aesthetics ................................................................................................................ 44

5.1.5.

Safety ...................................................................................................................... 44

5.2. ECONOMIC VIABILITY OF THE NAIL MAKING MACHINE ................................... 45 CHAPTER 6: CONCLUSION AND RECOMMENDATIONS ........................................... 48 6.1.

CONCLUSION .............................................................................................................. 48

6.2.

RECOMMENDATIONS ............................................................................................... 49

REFERENCES .......................................................................................................................... 50 APPENDICES ........................................................................................................................... 51

vi

LIST OF TABLES Table 4.1: Mechanical Properties of carbon steel grade ............................................................... 17 Table 4.2: Bearing materials and their properties ......................................................................... 18 Table 4.3: Dimensions of standard V-belts according to IS: 2494 - 1974 .................................... 24 Table 4.4: Standard pitch lengths of V-belts according to IS: 2494 - 1974.................................. 24 Table 5.1: Total Initial investment ................................................................................................ 46 Table 5.2: Operation costs ............................................................................................................ 46 Table 5.3: Cash flow per month .................................................................................................... 47

vii

LIST OF FIGURES Figure 2.1: Classification of nails ................................................................................................... 5 Figure 3.1: Model of Nail making machine from Punjab, India ................................................... 11 Figure 3.2: Nail making machine from USA ................................................................................ 12 Figure 3.3:N6-E Nail Making Machine ........................................................................................ 13 Figure 4.1: Flywheel ..................................................................................................................... 21 Figure 4.2: Belt-Pulley free body diagram ................................................................................... 26 Figure 4.3: Crankshaft .................................................................................................................. 27 Figure 4.4: Bearing ....................................................................................................................... 27 Figure 4.5: Connecting rod ........................................................................................................... 28 Figure 4.6: Roller .......................................................................................................................... 29 Figure 4.7: Cam ............................................................................................................................ 30 Figure 4.8: Cam and roller system ................................................................................................ 30 Figure 4.9: Nail head punch .......................................................................................................... 31 Figure 4.10: Cutting die lever ....................................................................................................... 34 Figure 4.11: Cutting die lever analysis ......................................................................................... 35 Figure 4.12: Cutting die free body diagram .................................................................................. 35 Figure 4.13: Cutting dies............................................................................................................... 36 Figure 4.14: Graph of displacement, x verses time ...................................................................... 38 Figure 4.15: Nail exit plate ........................................................................................................... 39

viii

ABSTRACT The objective of the research was to design a nail making machine that is cost effective for the cottage industry, to prepare a computer simulation model of the designed nail making machine and to determine the technical and economic viability of the new innovation. A survey of nail making machines currently used in the local cottage industry was carried out to establish how much they cost and their source. This was to give an overview on the need to have a cheaper design which is simple and cost effective. This involved collection of resources from different sources, visits to various industries to obtain important data for the project and having a guideline on the steps involved in the design. Among the sources of information looked at is the internet, reference books from the library and consultant engineers in the industry. From the survey, it was found out that the nail making machines currently in use in the country are very few and were imported from USA, China or India and they came at a cost of between Kshs. 600,000 and Kshs. 5,000,000. For this reason, they are only purchased by well established companies. A design of nail making machine innovation was then made using the Autodesk Inventor design software. A technical and economic evaluation of the design were carried out in terms of performance, environmental factors, maintenance, aesthetics/ergonomics, size and weight, safety and cost. The designed nail making machine costs about Kshs.95,324 to produce. From this project, it was shown that it is economical to manufacture the new design of nail making machine locally since the Kshs. 95,324 is much lower than the imported machines that cost more than Kshs. 600,000.

ix

CHAPTER 1: INTRODUCTION 1.1. NAILS, NAIL MAKING AND NAIL MAKING MACHINE

1.1.1. Nails Nails are pin-shaped, sharp objects of hard metal or alloy used as fasteners. They are typically made of steel, often dipped or coated to prevent corrosion in harsh conditions or improve adhesion. This also helps to add to its aesthetics (decorative appearance) in addition to improving the gripping strength. Ordinary nails for wood are usually of soft, low carbon or mild steel while those for concrete are harder. Nails are driven into the work piece by a hammer, nail gun or an explosive charge and they hold materials together by friction in the axial direction and shear strength. Nails are used for various purposes and industries ranging from building and construction to carpentry. It is for this reason that the types of nails are many and varied. 1.1.2. Nail Making Wire is drawn through a series of dies to reduce it to the required diameter. The end of the wire is gripped and punched in a die with the shape of the nail head. It forms a head which is knurled for easy hitting while driving it into the work piece to be fastened. After this, depending on the length of the nail required, the wire is severed with a die that is formed in the shape of the sharp point. The complete nail at this stage goes through a collecting tray ready to be passed to the next stage which involves coating. 1.1.3. Nail Making Machine The major operations performed by a nail making machine include head forming, wire cutting and wire feeding. In head forming, there is the use of the nail head punch which is knurled at the tip. It derives its motion from the crankshaft which is driven by the motor. In the design of the head punch, strength should be considered, i.e. it should be able to hit the wire without surface abrasions 1

and should withstand high impact loads. It should also be hard enough to avoid chipping of the hitting surface. In wire cutting, the cutting dies are shaped in a way as to achieve the pointed ends of the nails. They should be strong and harder than the nail wire. During cutting, there are shearing forces which lead to the formation of the pointed end. The cutting dies, are timed so as to give way to the nail head punch. Wire feeding involves pushing the wire into the die block by a cam. The motion of the cam is tapped from the nail head punch support or from the crankshaft itself. The main consideration for this operation is on the timing in order to get the right length of the nail at the right time.

1.2. PROBLEM STATEMENT Nail making machines come at a price ranging from Kshs 600,000 – 5,000,000, inclusive of tax. This has led to the following problems: i.

Locking out potential players in the cottage industry

ii.

High cost of imported nails

iii.

Nail making machines imported at a high cost

With the design and development of a nail making machine which can be manufactured locally, the above problems will be eliminated. This will also lead to the achievement of industrialization as stipulated in the vision 2030.

2

1.3. STUDY OBJECTIVE This project aims to design a nail making machine suitable for the local cottage industry. Specifically, the objectives are as follows:i)

To carry out a survey of nail making machines currently used in the local cottage industry.

ii)

To design a nail making machine that is cost effective for the cottage industry.

iii)

To prepare a computer simulation model of the designed nail making machine.

iv)

To determine the technical and economic viability of the new innovation.

3

CHAPTER 2: LITERATURE REVIEW 2.1 Definition A nail consists of a metal rod or shank, pointed at one end with a formed head at the other that can be hammered into pieces of wood or other materials to fasten them together. Steel is the main material used in nail making. Aluminum, brass and other metals can also be used. The surface can be coated or plated to improve its corrosion resistance, gripping strength, or decorative appearance. The head, shank, and point may have several shapes based on the intended function of the nail 2.2 Background Before the 19th century, nails were manufactured by blacksmiths. Iron wire was placed on an anvil and one end was tapered with the flat side of the hammer to about an inch from the end to form the sharp edge of the nail. A notch was cut in the rod using the sharp end of the hammer. The sharpened end of the rod was then thrust into a tapered hole in the anvil and snapped off the short nail. The end of the nail was then flattened with four or five quick strikes of the hammer and popped out of the anvil hole with a quick, upward strike at the point. This is where nail making has evolved from. Nails may have been used in Mesopotamia as early as 3500 B.C. and were probably made of copper or bronze. Later, iron was used to make nails. Early nails were shaped, or forged, with hammers. They were usually made one at a time, and were consequently scarce and expensive. By the 1500s a machine was developed which produced long, flattened strips of iron, called nail rods. These strips could then be cut into lengths, pointed, and headed. Two early nail-making machines were patented by Ezekial Reed of the United States in 1786 and Thomas Clifford of England in 1790. These machines cut tapered pieces from flat iron sheet, then flattened the head. In rural areas, black-smiths continued to make nails from wrought iron right into the 20th century. The first machine to make nails from metal wire was introduced in the United States in about 1850, and this technique is now used to make most of the nails today. 4

2.3 Applications of nails Nails are on normal occasions used for joining pieces of wood or for fastening other materials to wood. Nails are simply hammered into place and are held there by friction. Some nails have roughened shanks so that they will hold better. Nails are used extensively in the residential housing construction. The average wood frame house uses between 20,000 and 30,000 nails of various types and sizes.

There is a tremendous variety of nails, since they are used for so many different purposes. The ordinary all-purpose nails used are called common nails. Finishing nails, used in furniture and cabinetwork, have very small heads that do not show on the finished work. Nails are available in different lengths and gauges, or diameters. Most nails have notches, or grooves, near the head so that they will hold better. Some have screw-like threads for extra holding power. Specially hardened nails, designed to be driven into concrete or masonry, have longitudinally grooved shanks for a tight grip. There are also special double-headed nails for nailing temporary structures.

2.4 Classification of nails

Figure 2.1: Classification of nails

5

Though not well defined, nails are categorized into three on the basis of their length. In general nails that are less than 1 inch (2.54 cm) in length are called tacks or brads. Nails 1-4 inches (2.54-10.16 cm) in length are called nails, while those over 4 inches (10.16 cm) are some-times called spikes. Box nails are wire nails similar to common nails except that they have thinner shanks and are not to be used for dimensional lumber framing construction requiring common nails. This is because box nails do not have as thick a shank as a common nail for a given penny size and as such have less holding power. Box nails are typically used on thinner wood material (like wood boxes) to reduce splitting. Upholstery nails are used to decorate furniture and are used to give the final touch in many different types of furniture.

2.5 Design The shank of a nail is usually designed to be round and smooth. Shanks with serrations, annular grooves, spiral flutes, or helical threads are used when a stronger, more permanent grip is required. Thermoplastic coatings may also be added to the shaft. These coatings heat up through friction while the nail is being driven, then quickly cool and set to lock the nail in place. The diameter of the shank is determined by the type of nail. The most typical nail point is a foursided tapered cut called a diamond point. Other nails may have a blunter point to prevent splitting certain woods. Chisel points, barbed points, needle points, and many others are sometimes used on specialty nails. There are special nails for tile roofing, hardwood flooring, shingles, rain gutters, wall board, sheet metal, and concrete. Some nails are designed to be driven by air-powered nail guns rather than by a hammer. There have even been new nails designed for specific applications in the aerospace industry.

6

2.6 Raw Materials Most nails are made of steel. Aluminum, copper, brass, bronze, stainless steel, nickel silver, monel, zinc, and iron are also used. Galvanized nails are coated with zinc to give them added corrosion resistance. Blued steel nails are subjected to a flame to give them a bluish oxide finish that provides a certain amount of corrosion resistance. So-called cement-coated nails are actually coated with a plastic resin to improve their grip. Some brads are given a colored enamel coating to blend in with the color of the material they are fastening. 2.7 The Manufacturing process

Wire Rod

Wire Drawing

Inspection

Descaling

Acid picking

Nail Making

Packaging

Polishing

Delivery

Figure 2.2: Nail manufacturing process

Wire is drawn from a coil and fed into the nail-making machine where it is gripped by a pair of gripper dies. The shape of the head of the nail has been machined into the end of the dies. While the dies clamp the wire in place, the free end of the wire is struck by a mechanical hammer. This deforms the end of the wire into the die cavity to form the head of the nail. With the wire still clamped in the dies, a set of shaped cutters strike the opposite end of the nail, forming the point and cutting the nail free from the rest of the wire coming off the coil. The dies open and an expelling mechanism knocks the nail into a collection pan below the machine. The free end of the wire is drawn from the coil and fed into the machine. The cycle then begins again. 7

2.8 The Future The demand for mass-produced commodity nails is dependent on the fluctuations in the construction industry, which varies with the economy. Demand for these nails is also subject to competition from foreign manufacturers, further reducing profits. In Kenya, nail production has not been embraced as the nail making machine is unaffordable. With the growth of the population and the economy, demand for housing is increasing and this consequently leads to an increase in demand for nails. Demand for these nails is also subject to competition from foreign manufacturers, further reducing profits. Desirable features of a nail making machine include: i.

Smooth operation

ii.

Less wear and tear

iii.

Low maintenance cost

iv.

High durability

v.

High efficiency

8

CHAPTER 3: METHODOLOGY The mission of this project was to design a cheap and affordable nail making machine for the cottage industry in Kenya. With the completion of this project we hope that our nail making machine design will be used widely throughout the cottage industry in Kenya. We also hope that by domestically manufacturing the nail making machine, the price of the machine will be drastically reduced and this will allow creation of job opportunities within the sector in addition to contributing towards the realization of the vision 2030. Initially, we made a factory visit to some nail industries in Kenya e.g. Wire Products in Athi River and Devki Steels in Ruiru where we found that the existing machines had been imported mainly from India. We also gathered literature from a number of resources regarding existing machine designs from other countries that manufacture them like China, USA and India. With this knowledge, we then developed design matrices to determine what made a reliable nail making machine and which features and mechanisms we would modify in order to come up with an affordable nail making machine. We thereafter developed CAD drawings using Autodesk Inventor of the same. The objective of this project will be achieved through the subsequent completion of the goals including analyzing all existing nail making design products and determining which one can easily be fabricated using the locally available materials and machines, producing a computer simulation using Autodesk Inventor and then determining the overall quality of the nail making machine e.g. in terms of cost of production.

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3.1. A Survey of Nail Making Machines Currently Being Used In the Cottage Industry Today’s technology offers many different nail making machine designs available for purchase by the manufacturing and the building industry. These machines are produced overseas by a wide variety of companies in countries like India, China and USA. The different available machines are designed for production of different nail designs. E.g. there are different machines for producing box nails, screw nails, finishing nails, cut flooring etc. and different machines for different inches of nails. Our main focus on the same was on the nail making machines that are small and efficient. Our secondary task was to decide on a machine design that most closely fit the needs of the Kenyan building and manufacturing sectors at a reasonable expenditure. 3.1.1. Current Nail Making Machine Designs The first step to evaluating nail making machine design was to find out what products were currently available in the industry. We asked around and realized that the nail manufacturers were very few. We found out that Devki Steels in Ruiru and Wire Products in Athi River were the only manufacturers of nails around. We started our research by visiting Devki Steels Ltd to view the machines they had. We met the maintenance engineer who gave us a history of how the company started making nails, imported mainly from India. He demonstrated the nail making process to us and the range of nails that they handle. We discovered that the company does not manufacture roof nails. He said they were some of the most expensive machines approximating at about US $ 8,000 and together with the shipping costs and taxes it would come to over US $ 10,000. He said that it was due to this that only a few companies could afford the machine but still with the very high cost it would only follow that the nails are manufactured and sold at a high cost. This, he said, was the reason for the unfair competition from nails imported as they came cheaper which led to them not being able to work on a full capacity as the demand was lower for locally manufactured nails. We then did an online research for nail making machines that are currently being imported mainly from India, China and USA. Our search led us to the following designs.

10

3.1.2. Perfect Automatic Wire Nail making machine This is a model which is manufactured in Punjab, India.

Figure 3.1: Model of Nail making machine from Punjab, India

It is simple and sturdy in design and is made from high grade casting & steel. There is a range of them which can produce flat head nails, pop nails, round head nails, lost head nails, counter sunk head nails, from copper, aluminium & brass Wires. Its main crank is directly driven by motor and side-shafts are driven by four bevel gears to ensure correct and permanent adjustment of the cutting tool. The length and thickness of the nails is adjustable. All tools are easily accessible and can be quickly changed. Its main and side shafts are fitted with bushes to ensure long life. All cams, gears, rollers, roller pins are made from highquality steel properly heat-treated and grounded for long lasting. The wire end from coil passes through straightening rollers and fed intermittently in the gripping dies, which close firmly allowing heading punch to press the head of the nails, then grip loosened and required length of the nail is fed constantly, where it is cut by cutting tools leaving ample stock for the head of the next nail. Thus ready nail is ejected by the ejector. The operations are repeated in each revolution. This goes at Kshs. 166,000 before adding the shipping costs. This would therefore get to over Kshs. 300,000. 11

3.1.3. Nail making machine – USA

This is an invention from United States of America.

Figure 3.2: Nail making machine from USA

Just like the upper one, it also involves the application of a main shaft and side cams. These act as the main power transmission system to the dies. It however differs from the above in several respects which enable to operate at a higher speed.

12

The features of this machine resides in driving the reciprocating heading ram by means of a balanced flywheel and crank construction which enables the crankshaft to be driven at a higher speed in complete balance, in spite of the rapidity with which the ram forms the nail heads. The machine also provides a continuously rotating ejector for positively clearing the cut nails from the machine with the ejector operating in perfect timed relation with the heading ram. Other features of the machine include a mechanism for operating the wire grippers by means of preloaded torsion members which cause the grippers to firmly hold the wire during the heading operation, with provision for unloading the gripping members only when the wire is being fed after the heading operation. These are the main differences between this machine and the one from Punjab, India.

3.1.4. N6-E Nail Making Machine

Figure 3.3:N6-E Nail Making Machine

This nail making machine is also manufactured in USA. In this case, the wire form wire coil passes through straightening rolls and fed intermittently into the gripping dies which close firmly head of the nail. The grip is loosened now and the required length of wire is fed forward. Then the cutting tools cut the point a little forward of the grip 13

leaving sufficient wire projecting to form the head of the next nail. This sequence of operations is repeated at each revolution of the machines and the nails are produced constantly.

The frame of the machine is rigid; all moving parts are of ample dimensions and precisely made from quality material which ensures the smooth running of machine in spite of high rate of output. The wire feed is actuated by means of gears mounted on one side shaft which moves the feed slide through connecting rod. The bush bearings are made from special metals and provided with continuous approach of oil which ensures the smooth running and long life. This comes at a cost of Kshs. 400,000.

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CHAPTER 4: DESIGN OF NAIL MAKING MACHINE 4.1.SELECTION OF MATERIALS When selecting the materials from which the different components of the nail making machine is to be made, we first defined the requirements that are associated with its performance when in service and with its manipulation into the shape of the product. The machine will work at a speed of approximately 1400rpm and this requires that the fatigue strength of the moving components be high. The overall weight of the machine is big due to the flywheel, die block and other components. This requires that the mountings be able to hold that weight for a long period. Due to the movement of the dies and the punch from the motor through the crankshaft, there exists vibrations in the machine that have to be taken note of during the design of the nail making machine. Impact forces are experienced on the nail head punch and the cutting dies for nail formation and wire severing respectively, the material of the two components must, therefore take those forces for a long time without fail. They should also be hard and strong to avoid surface abrasions or chipping off. Secondly, we obtained a balance between these requirements and the properties and other characteristics of the materials that are available with regard to the economic considerations as per the project objectives. The flywheel, for example, could be made from carbon fiber material and employ magnetic bearings but this is not used in this design due to the availability and cost of those materials. Manufacturing methods contribute to the cost of the machine so while designing, we considered parts that are easily and cheaply machined. The main material chosen for the nail making machine is mild steel. This is used in the mountings, L section beams and frame structures. It has the following properties:i)

In mild steel composition, other than maximum limit of 0.02 carbon in the manufacture of carbon steel, the proportions of manganese, copper and silicon are fixed, while the proportions of cobalt, chromium, niobium, molybdenum, titanium, nickel, tungsten, vanadium and zirconium are not.

15

ii)

A high amount of carbon makes mild steel different from other types of steel. Carbon makes mild steel stronger and stiffer. However, the hardness comes at the price of a decrease in the ductility of this alloy.

iii)

Carbon atoms get affixed in the interstitial sites of the iron lattice and make it stronger.

iv)

Density is 7.85 gm/cm3

v)

Young's modulus, is 210 Mpa

vi)

It has ferromagnetic properties, which make it ideal for manufacture of and motors

vii)

The high amount of carbon also makes mild steel vulnerable to rust.

These factors make steel be suitable as the main material of the nail making machine.

4.1.1. Head Punch and Cutting materials High strength carbon steel is used for the nail head punch and the cutting dies. These have to be hardened to be able to take the impact forces. In addition to that, they should be able to deform the low carbon mild steel for the nail wire. The nail wire mild steel has a composition of 0.05% to 0.26% carbon content with up to 0.4% manganese content. 4.1.2. Crankshaft Material The crankshaft is the main connection and transmitter of power from the motor to the nail head punch hence it should have the following properties for it to work well. It should have:i)

High strength

ii)

Good machinability

iii)

Low notch sensitivity factor

iv)

Good heat treatment properties

v)

High wear resistant properties

16

For ordinary shafts, the material used is carbon steel of grades 40C 8, 45C 8, 50C 4 and 50C 12. The mechanical properties of these grades of carbon steel are given in the table below:Indian standard

Ultimate tensile

Yield Strength, MPa

designation

strength, MPa

40 C 8

560 – 670

320

45 C 8

610 – 700

350

50 C 4

640 – 760

370

50 C 12

700 Min.

390

Table 4.1: Mechanical Properties of carbon steel grade

4.1.3. Fastener Materials Bolts and nuts for the nail making machine can be made from carbon steel or alloy steel. Carbon steel is the cheapest and most common bolt material. Most hardware stores around sell carbon steel bolts, which are usually zinc plated to resist corrosion. The typical ultimate strength of this bolt material is 379Mpa. Alloy steel is a high-strength carbon steel that can be heat treated up to 2.068 GPa. However, it is not corrosion resistant and must therefore have some type of coating to protect it from corrosion.

17

4.1.4. Pulley Material For the pulleys, the most preferred material is cast iron. This is chosen due to the following properties. Tensile strength – this is about 483Mpa. Compressive strength is high and can be almost as high as that of mild steel. Cast iron also shows resistance to deformation. 4.1.5. Bearing Material Bearings should have properties like good fatigue strength, comformability, embedability, antiscoring, corrosion resistance and thermal conductivity. From the following table of bearing materials and their properties, it can be noted that there is not one material with all the above hence a trade-off has to be made to get a material with the best combination of properties.

Bearing material

Fatigue strength

Tin base babbit

Poor

Lead base babbit

Comformability

Embedability

Antiscoring

Good

Excellent

Excellent

Excellent

Poor

Poor to fair

Good

Good

Good to excellent

Fair to good

Poor

Lead bronze

Fair

Poor

Poor

Poor

Good

Fair

Copper lead

Fair

Poor

Poor to fair

Poor to fair

Poor to fair

Fair to good

Aluminium

Good

Poor to fair

Poor

Good

Excellent

Fair

Silver

Excellent

Almost none

Poor

Poor

Excellent

Excellent

Silver lead deposited

Excellent

Excellent

Poor

Fair to good

Excellent

Excellent

Table 4.2: Bearing materials and their properties

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Corrosion resistance

Thermal conductivity

From the above table and the design considerations of the nail making machine, the best choice is aluminium. This is due to its availability and good fatigue strength, corrosion resistance and thermal conductivity. 4.1.6. Die block Material The die block can be made of cast iron or cast steel. Cast iron is eliminated in this case due to its brittleness hence its inability to take repeated impact loads during head formation of the nail. 4.1.7. Flywheel Material Flywheels rotate at speeds of up to 60,000 rpm and this is the main consideration when choosing a material for the same. The force on a flywheel increases with speed and the energy a wheel can store is limited by the strength of the material from which it is made. If you spin a flywheel too fast you eventually reach a point where the force is so great that it shatters the wheel into fragments. Strong lightweight materials turn out to be the best for flywheels since they can spin fastest without breaking apart. Steel being the locally available material and cheap is used in this case. The spring can be purchased locally and the types made from annealed steel can be used. 4.1.8. Nail collector material This is made from sheet metal. It can be galvanized in order to prevent corrosion.

19

4.2.SELECTION OF MANUFACTURING METHODS FOR PARTS During the selection, we considered the size, shape of the components, required strength and the material from which it is to be made. In addition to this, we looked at the economics of quantity and cost, time allowed to manufacture the product and the locally and easily available manufacturing tools and machines. Putting all the above into consideration led us into selecting the best manufacturing method for each component. The frames and mountings of the machine made from L-channels and square pipes and blocks are simply machined. In this case, a power saw can be used to cut the parts into the required sizes and shapes. This method is cheap and faster especially given the number of parts that are supposed to be cut. It is also fast hence reduces the time for manufacture of the machine. The flywheel is big and machining would be difficult and time consuming. The most preferred method of manufacturing would therefore be casting. The number of steel furnaces is small locally but the flywheels can easily be found from the hardware stores around. Due to its good machine ability, the nail collector made of iron sheet is simply machined using hack saws or using gas cutting method. It does not involve extensive machining. The material is also sufficiently ductile hence this allows for cold working without splitting. There are various methods for production of the crankshaft. One method is turning a piece of bar material on a lathe. It can also be made up of sections that are bolted together. Another method is by forging or casting. Forging would produce stronger crankshaft than casting but at a higher cost. It is also not readily available due to the expensive manufacturing equipment. This therefore leads us to the option of casting since it is cheaper and can easily be done without removing so much material at the machining stage. The die block could also be manufactured by casting since it is a little complicated. Various small components are held together by welding since most of them cannot be made as a single component. This would make the cost of fabrication by this method lower than that of casting.

20

4.3.DESCRIPTION OF PARTS OF DESIGNED NAIL MAKING MACHINE The designed nail making machine has six major systems namely: 1. Power/Driving system 2. Wire feeding system 3. Head forming system 4. Nail cutting system 5. Machine fixture system 6. Nail exit system. 4.3.1. POWER/DRIVING SYSTEM This provides the driving force for all the components of the machine. This system is composed of the motor, flywheel, pulley system, crankshaft and the connecting rod. 4.3.1.1.

Motor

The machine uses an a.c. motor with the following specifications:i)

1.5kW

ii)

1400 rpm

This will go with a wire of 12 S.W.G.(standard wire gauge) 4.3.1.2.

Flywheel

Figure 4.1: Flywheel

This is a heavy wheel attached to the rotating crankshaft to smooth out delivery of power from the motor to the nail head punch through the crankshaft. The rotating mass is used to maintain 21

the speed of nail making machine while the machine releases or receives energy at a varying rate, i.e. as the nail head punch hits the nail to form the head and while the cutting dies are severing the nail wire. The motor starts at a low speed and accelerates and while the flywheel also accelerates, it stores energy which it gives back to the crankshaft as the speed decreases. The inertia of the flywheel opposes and moderates fluctuations in the speed of the engine and stores the excess energy for intermittent use. The amount of energy stored in a flywheel is proportional to the square of its rotational speed, πœ” as seen in the equation below; 1 𝐸 = πΌπœ”2 2 Where: E is the energy stored ω is the angular velocity I is the moment of inertia of the mass about the center of rotation. The moment of inertia is the measure of resistance to torque applied on a spinning object (i.e. the higher the moment of inertia, the slower it will spin when a given force is applied). The moment of inertia for a solid cylinder is

,

Where m denotes mass and r denotes a radius. Energy is transferred to a flywheel by applying torque to it, thereby causing its rotational speed, and hence its stored energy, to increase. Here, the actual shearing and forming are done in only a fraction of the operating cycle. During the longer, non-active period, the speed of the flywheel is built up slowly by the motor. When the press is operating, most of the required energy is provided by the flywheel. Its ability to deliver energy at rates beyond the motor makes it good for the nail making machine. From the basic laws of physics, the flywheel will store more energy if it has either a higher moment of inertia (more mass or mass positioned further from its centre) or if it spins at a

22

higher speed and since the kinetic energy of a spinning object, E, is related to the square of its angular velocity, speed has a much bigger effect than moment of inertia. The standard dimensions of a rectangular sunk key for a shaft of diameter 1.5 inches are as follows: Width of key = 0.375 inches Thickness of key = 0.1875 inches 4.3.1.3.

Pulley system

This is composed of the belt drive and pulleys. The rotary motion of the motor is transferred to the crankshaft through the belt and two pulleys, one at the motor shaft and the other at the crankshaft. The v-belt is suited for the nail making machine for the following reasons:i.

It is the cheapest power transmission utility

ii.

Does not require axial alignment.

iii.

Easy installation and removal

iv.

Quiet operation

v.

Cushion the motor and bearings against load changes.

V-belts are made of fabric and cords and molded in rubber while the pulleys are made of cast iron in order to reduce the overall weight of the machine.

23

From Indian standards, the dimensions are as below.

Type of belt

Power ranges in kW

Minimum pitch diameter of pulley (mm)

Top width (mm)

Thickness (mm)

Weight per meter length (N)

A

0.7 – 3.5

75

13

8

1.06

B

2 – 15

125

17

11

1.89

C

7.5 – 75

200

22

14

3.43

D

20 – 150

355

32

19

5.96

E

30 - 350

500

38

23

-

Table 4.3: Dimensions of standard V-belts according to IS: 2494 - 1974

From this and with a motor rating of 1.5kW, the suitable choice is class A with a pitch length of 1255mm. For the pitch length, the standards for class A are as in the table below:

Type of

Standard pitch lengths of V-belts in mm

belt

A

645, 696, 747, 823, 848, 925, 1001, 1026, 1051, 1102, 1128, 1204, 1255, 1331, 1433, 1458, 1509, 1560, 1636, 1661, 1687, 1763, 1814, 1941, 2017, 2068, 2093, 2195, 2322, 2474, 2703, 2880, 3084, 3287, 3693. Table 4.4: Standard pitch lengths of V-belts according to IS: 2494 - 1974

With the consideration on the distance from the motor shaft to the crankshaft pulley and the above standard pitch lengths of V-belts for class A, the suitable length is 1560mm.

24

The v-belt speed can be calculated as follows:𝑣 = πœ”π‘Ÿ =

=

2πœ‹π‘ π‘Ÿ 60

2πœ‹ × 1400 × 0.03 60 = 4.398 π‘š/𝑠

The diameter of the driven pulley (crankshaft pulley), d2 is calculated as follows: 𝑁1 𝑑2 = 𝑁2 𝑑1 Where N1 and N2 are the angular speeds of the motor and driven pulleys respectively and d1 and d2 are the diameters of the motor and driven pulleys respectively. 𝑑2 =

=

𝑁1 𝑑1 𝑁2

1400 × 60 350

= 240π‘šπ‘š The driven pulley at the crankshaft will therefore have a diameter of 240mm. With the chosen belt pitch length of 1560mm, the distance between the driven and driving pulleys is computed as below:

25

Motor pulley

Driven Pulley α

X Figure 4.2: Belt-Pulley free body diagram

𝑆𝑖𝑛 𝛼 =

π‘Ÿ2 − π‘Ÿ1 π‘₯

=

𝑑2 − 𝑑1 2π‘₯

𝐿 = πœ‹ π‘Ÿ2 + π‘Ÿ1 + 2π‘₯ +

π‘Ÿ2 − π‘Ÿ1 π‘₯

1560 = πœ‹ 120 − 30 + 2π‘₯ +

2

120 − 30 π‘₯

2

2π‘₯ 2 + 150πœ‹ − 1560 π‘₯ + 902 π‘₯ = 536.84π‘šπ‘š

26

4.3.1.4.

Crankshaft

This can be described as an off-centre connection that takes energy from a rotating wheel. Its primary function is to convert rotary motion from the motor to a reciprocating motion required for the head formation by the nail head punch. It can be forged from a steel bar through roll forging or cast in ductile steel. The crankshaft carries high torsion loads and needs to have high fatigue strength. It should also have a good hardness to resist surface abrasion and wear by the parts attached to it. For the nail making machine, the crankshaft will be composed of pieces of shafts attached together as shown below.

Figure 4.3: Crankshaft

This is to reduce on the cost that could be incurred during casting. 4.3.1.5.

Bearings

The bearings are used between the crankshaft and the machine frame to maintain separation between the two components. This serves to reduce frictional resistance due to relative motion between contact surfaces.

Figure 4.4: Bearing

27

They should be lubricated in order to reduce friction and wear between the sliding parts of the bearing, dissipate the heat that arises during the nail cutting process, protect the bearing surfaces from water, dirt, etc or to prevent corrosion of the bearing surfaces. The lubrication process forms part of the regular maintenance measures and oil or light grease is used for this purpose. 4.3.1.6.

Connecting rod

The motor rotates the crankshaft which transmits the motion to the nail head punch. In order to do this and maintain the nail head punch motion on a straight line, the connecting rod is used. This is attached to the crankshaft with bushes between them to avoid wear and tear on the two components.

Figure 4.5: Connecting rod

Together with the crank, they form a simple mechanism that converts rotary motion into linear motion. Since the connecting rod is rigid, it may transmit either a pull or a push thus the crankshaft can be used while pushing and pulling the nail head punch through both halves of a revolution. The connecting rod is linked to the crankshaft by a bush. The most commonly used bushes are split bushes. Without the bushes, the connecting rod and the crankshaft would wear out necessitating replacement which is expensive and time wasting. With the bush in place, this effect is eliminated as it undergoes the wear and tear instead. For this reason, the bush should have a good high load bearing material. The split bushes used in the nail making machine can be cast thus reducing machining time. For this machine, the bush is made from bronze and requires regular lubrication. 28

4.3.2. WIRE FEEDING SYSTEM The basic function of this system is to provide the machine with the raw material for nail making, i.e. the wire. It comprises various components as illustrated all of which play particular roles in the nail making process. They are:4.3.2.1.

The Rollers

The nail wire is normally kept and moved in rolls. During uncoiling, therefore, there is the tendency of the wire not to be straight. This could cause a problem during head forming as the wire could buckle. To avoid this, the rollers are used. They have a function of straightening the wire as it enters the die block and to remove the effect on the wire due to case hardening since this would necessitate large cutting forces and cause fast wear and tear on the cutting dies.

Figure 4.6: Roller

The rollers used in the machine are five in number placed two on one side of the wire and three on the other. They are mounted on two metallic slabs which can be easily separated and closed by the use of a bolt with a wing nut during the initial feeding of the wire into the machine. 4.3.2.2.

The Cam

This offers a controlled wire entry into the die block which ensures that the correct length of the wire is fed depending on the size of nail required. It also ensures uniformity of the nails in size.

29

Figure 4.7: Cam

As can be shown in the diagram below, the cam is profiled in such a way that it moves the wire by a certain distance in every revolution.

Figure 4.8: Cam and roller system

The cam presses the wire against the roller hence grasps it. The surface (gripping surface) is hardened to prevent fast wear and tear and to ensure that a considerable force is generated do pull the wire from the rotating roll which is placed next to the machine. After pushing the wire into the die block to the required length (2 inches in this case) the cam rotates freely and the wire is left stationary. This is the time during which the nail is cut and the wire hit to form the head for the next nail. The cam drive is attached to the nail head punch where it draws its motion. 4.3.2.3.

The nail feeder support

It is attached to the die block and carries five straightening rollers and a single roller which helps to grip the wire as it is being pushed by the cam. It also acts as the support of the wire as it goes into the machine.

30

4.3.3. NAIL HEAD FORMING SYSTEM This system forms the wire tip hence making it conform to the required shape of the nail head. The nail head forms the hitting surface when using the nail as a fastener. The major component of this system is the nail head punch. 4.3.3.1.

Nail head punch

The function of this is to hit the wire tip hence making it conform to the required shape of the nail head. Its tip is knurled to form the surface necessary for providing friction while using the nail. It is made of high carbon, heat-treated steel for strength and durability. The heat treatment helps prevent chipping or cracking caused by repeated blows on the cut wire. It needs to be strong and sturdy. It should be hard to prevent cracking and chipping during hitting. It is connected to a support which transfers motion from the crankshaft through the connecting rod.

Figure 4.9: Nail head punch

The auxiliary components which support and guide the nail head punch include; die block, wire gripper, nail guide and the nail head punch cover. Force required to forge the nail head can be calculated as below:Stress, 𝜍 is given by: 𝜍 =

πΉπ‘œπ‘Ÿπ‘π‘’ π΄π‘Ÿπ‘’π‘Ž

Making force the subject of the formula, πΉπ‘œπ‘Ÿπ‘π‘’ = π‘†π‘‘π‘Ÿπ‘’π‘ π‘  ∗ π΄π‘Ÿπ‘’π‘Ž Area of wire acted upon by the force of the nail head punch is given by: π΄π‘Ÿπ‘’π‘Ž =

πœ‹π‘‘ 2 4

, where d is the diameter of the wire 31

π΄π‘Ÿπ‘’π‘Ž =

πœ‹(0.118∗2.5∗10−2)2 4

= 7.055 ∗ 10−6 M2

The yield strength of mild steel is, 𝜍 = 248 MPa ∴ The force 𝑃 = 248 ∗ 106 ∗ 7.03539 ∗ 10 − 6 = 1749.7 𝑁 = 1750 𝑁 The density of the nail head punch material is 7.85g/cm3 The linear speed of the nail head punch can be calculated as follows:The motor speed is 1400 rpm From ω =

2πN 60

N=1400 r.p.m Then ω =

2∗π∗1400 60

= 146.6 rad/sec

From v = ωr, r =1.5x2.54x10-2 =0.0381m The linear speed of the nail head punch is v =146.6x0.0381 = 5.585m/s The momentum of the nail head punch is given by Momentum = mv,

where

m = mass v = linear velocity

The mass of the nail head punch can be estimated as follows. Mass = πœŒπ‘‰ ,

where

𝜌 = density V = volume

The minimum force required to forge the nail is 1750N as determined above. Putting a safety factor of 2, the actual force imparted on the nail wire is 1750X2 = 3500N.

32

4.3.3.2.

Die block

The wire passes through the die block and is hit to form the nail head on the front side. The front end of the die block where the wire emerges is in the shape of the nail head. The die block also houses the gripper which is operated by the motion of the nail head punch. 4.3.3.3.

Wire gripper

During the forging of the nail head, there is need to hold the wire tightly to prevent it from receding during the formation of the nail head. This is because of the large force involved while forging the head. It is timed in such a way that it releases the wire immediately the head is formed to allow more wire to be fed into the machine. 4.3.3.4.

Rail guide

The primary function of this is to align the nail head punch with the central axis of the machine so that it always hits the nail at the required position without deflection. It also offers support to the nail head punch (forms the nail head punch rest) 4.3.3.5.

Nail head punch cover

By construction, the nail head punch would deflect in a vertical direction upon punching the nail head. To prevent this, the nail head punch cover is employed to restrict this deflection.

33

4.3.4. NAIL CUTTING SYSTEM This severs the wire with the head already formed from the rest of the wire. Its components include the nail cutting die, cutting die lever, sliding roller, cutting die head rail and the return spring. 4.3.4.1.

Sliding roller

This slides on the surface of the nail head punch and remains on the same position lengthwise as the head punch reciprocates. The sides of the nail head punch are profiled such that when the head punch is at extreme backward position, the nail cutting dies are at the cutting position. The sliding rollers enable this motion with ease as the friction is reduces. 4.3.4.2.

Cutting die lever

This is to drive the nail cutting dies. They push the cutting dies to the cutting position and are themselves pushed back by the return spring.

Figure 4.10: Cutting die lever

The Stress due to the Bending Moment that the cutting die levers must overcome is calculated as follows: The bending stress is given by πœπ‘π‘’π‘›π‘‘π‘–π‘›π‘” = Where and

𝑀 𝐼

𝑑

∗2

𝑀 = 𝑑𝑕𝑒 π‘šπ‘Žπ‘₯π‘–π‘šπ‘’π‘š 𝑏𝑒𝑛𝑑𝑖𝑛𝑔 π‘šπ‘œπ‘šπ‘’π‘›π‘‘, 𝑑 = π‘‘π‘•π‘–π‘π‘˜π‘›π‘’π‘ π‘  π‘œπ‘“ 𝑑𝑕𝑒 π‘π‘’π‘Žπ‘š

34

𝐼 = 𝑑𝑕𝑒 π‘šπ‘œπ‘šπ‘’π‘›π‘‘ π‘œπ‘“ π‘–π‘›π‘’π‘Ÿπ‘‘π‘–π‘Ž

The moment of inertia I is given by,

𝐼=

𝑏𝑑 3 12

=

2×2.54 ×10 −2 ×(2 ×2.54 ×10 −2 )3 12

= 5.55 × 10−7

Computing the stress due to the bending moment: The cutting die lever can be modeled as a simply supported beam as illustrated in the diagram below:

P

𝐿 2

L Figure 4.11: Cutting die lever analysis

This can be represented in a free body diagram as follows

P P

R1

R2 Figure 4.12: Cutting die free body diagram

R1 and R2 are the reactions at the ends due to the central load P

35

From the balance of clockwise and anti clockwise moments, R1 and R2 are found to be: 𝑅1 = 𝑅2 = 1750 𝑁 The resulting bending moment will be maximum at the center where P acts and is given by: π‘€π‘šπ‘Žπ‘₯ = 1750 × 8 × 2.54 × 10−2 = 355.6 ≅ 356 π‘π‘š The stress due to the maximum bending moment experienced at the centre of the cutting die levers is given by, πœπ‘π‘’π‘›π‘‘π‘–π‘›π‘” π‘šπ‘Žπ‘₯ =

𝑀 𝑑 356 2 × 2.54 × 10−2 × = × = 16.27 × 106 ≅ 16.3 π‘€π‘ƒπ‘Ž 𝐼 2 5.55 × 10−7 2

The cutting die levers should be designed to overcome this stress i.e. the levers should have higher bending stress strength so that the nail machine does not fail due to this stress. This is the same stress that is transferred to the screw hence the screw is designed to overcome this. 4.3.4.3.

Nail cutting die

Immediately after the nail head formation, the nail head punch moves back as the nail is moved forward by the cam. The cutting die levers then close in pushing the cutting die which cuts the wire which then falls on the exit plate. The cutting die become blunt after some time hence need to be sharpened from time to time.

Figure 4.13: Cutting dies

36

4.3.4.4.

Return spring

The levers do not have a return mechanism and the return spring is necessary. It pushes the cutting die holder which in turn pushes the levers back. Without being pushed back, the nail head punch would hit it hence causing breakage of the machine. A compression spring is used for this purpose. When the spring is compressed, the force it exerts is proportional to its change in length. The rate or spring constant of a spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve.

where x is the displacement vector – the distance and direction the spring is deformed from its equilibrium length. F is the resulting force vector – the magnitude and direction of the restoring force the spring exerts k is the rate, spring constant or force constant of the spring, a constant that depends on the spring's material and construction. This push is what is required to return the cutting dies to the open position in order to give space for the nail head punch to hit the nail head. Since force is equal to mass, m, times acceleration, a, the force equation for a spring obeying Hooke's law looks like:

37

X Amplitude

Period

Figure 4.14: Graph of displacement, x verses time

The displacement, x, is a function of time. The spring in this case stores potential energy which is then dissipated after the nail cutting levers have released the nail cutting die to push it back to the open position.

4.3.4.5.

Cutting die head rail

This houses the return spring and the cutting die holder. It holds the two in position to ensure that there is no sideways deflection while the machine is in operation.

38

4.3.5. MACHINE FIXTURE SYSTEM This comprises of the mountings to hold the machine in position. They are made from steel and should be strong enough to hold the machine in position. It should also be able to hold against the vibrations that occur during the cutting and head formation. On the lower foundation are L-shaped beams which can be screwed to the ground to make the machine more stable and resist the vibrations.

4.3.6. NAIL EXIT SYSTEM This is composed of a collector that directs the formed nails out of the machine for collection. It is made from sheet metal and has a slope downwards that enables the nails to easily slide out of the machine after being severed. It runs from the end of the nail head punch stroke and projects out of the machine. It should be wide enough to be able to collect nails that may jump while from the cutting dies.

Figure 4.15: Nail exit plate

39

4.4.WORKING PRINCIPLE OF INNOVATION

40

The innovation uses a motor which when started, rotates the crankshaft connected to it through a V-belt and pulley drive. The end of the crankshaft is attached to a flywheel in order to smooth out the motion of the crankshaft. The crankshaft is connected to the nail head punch through the connecting rod. The rotary motion of the crankshaft is converted to a reciprocating motion of the nail head punch support. This reciprocating motion of the nail head punch is used during the nail head formation as it intermittently hits the end of the nail wire. The motion of the nail head punch is also used by the nail cutting system. There exists push levers which push the cutting dies at one end once the nail head has been formed. At

the

opposite end of the push levers, there are rollers that slide on the sides of the nail head punch. These are included to reduce friction between the levers and the nail head punch contact surface. The sides of the nail head punch are profiled in such a way that as the nail head punch hits the wire to form the nail head, the cutting dies are fully open and while the nail head punch is at its extreme back position, the cutting dies sever the wire to form the nail. The wire feeding system also derives its motion from the nail head punch. The reciprocating motion of the nail head punch is converted to a rotary motion of the cam through an off-center pivot on the cam. The cam is placed side to side with a roller between which the wire passes. The roller rotates freely and provides the required pressure necessary for the cam to grip the wire. The gripping of the wire is necessary to pull more wire from the wire roll placed next to the machine. The cam is shaped in a way that during one rotation, only a fraction of the circumference of the cam grips the wire. This fraction is equal to the length of the nail to be cut. For the rest of the circumference of the cam, the cam rotates freely without feeding the wire and it is during this time that the cutting dies sever the nail wire and then the head punch forms the head. During the head formation, so much force from the nail head punch is used to forge the severed protruding end of the wire to conform to the nail head cavity on the die block. There is need therefore, to hold the wire during the forging to prevent it from receding. A wire gripping mechanism is introduced at the die block. A wire gripper is attached to the nail head punch from which it derives its to and fro motion. There is a small hole on the die block that goes up to the 41

wire groove in which a small metallic block is inserted. As the nail head punch advances, the nail gripper slides on the small block pushing it downwards against the wire hence providing the grip. Once the nail has been severed, it falls on a collecting tray made of sheet metal which directs it out of the machine. This collecting tray is sloping hence the nails move through it by gravity. This nail making machine can also be modified to produce nails of up to 3inches. This can be done by replacing the cam with another one of a different profile that feeds the required size of the nail. The innovation is different from existing machines since the driving system for major components notably the nail cutting system and the nail feeding system. The description of the working mechanism is as below:

42

CHAPTER 5: DETERMINATION OF TECHNICAL AND ECONOMIC VIABILITY 5.1. TECHNICAL VIABILITY OF NAIL MAKING MACHINE In the analysis of the nail making machine in terms of technical viability, we took into account factors such as performance, environmental factors, maintenance, aesthetics/ergonomics, size and weight and safety. These are outlined below: 5.1.1.

Performance

In Kenya, electrical power is supplied at a rating of 240V, 50Hz. The nail making machine will use a motor of 2Hp and 1400rpm. From this and a pulley reduction factor, the machine will operate at a rate of 350cycles per minute. With the production of one nail per cycle, the rate of production of nails will be 350 nails per minute. The nail making machine is designed to run continually for 12 hours. The crankshaft and the nail head punch are well lubricated in order to reduce the friction. Friction increases the temperature on the mating surfaces. With adequate lubrication, there is minimal friction on the components leading to minimum heat generation. Since the amount of heat generated is little, air-cooling is sufficient to run the machine for a long time without overheating. The nail making machine is also designed to produce 2 inch nails. However, provision of a cam with a different profile can enable it to produce nails of different sizes. In order to eliminate the vibrations occurring in the machine due to the reciprocating motion of the nail head punch and the rotational motion of the flywheel, vibration isolators can be installed together with the machine. 5.1.2.

Environment

The nail making machine can operate indoors and outdoors under normal working conditions. A motor insulation and protection is required to ensure that there is no sparking or arcing during operation due to the vibrations that are experienced during the operation of the nail making machine. The machine has a motor cage that ensures that the ingress of dirt dust and grease does not affect the operation of the nail making machine. 43

5.1.3.

Maintenance

Frequent lubrication of the nail making machine should be carried out. In addition to this general observation should be made i.e. to ensure that all the joints, bolts and nuts are well secured. For the above nail making machine innovation, maintenance takes a short time since it is smaller and most parts can be easily accessed. 5.1.4.

Aesthetics

The nail making machine is painted in blue and white to give it a fine finish. The color can also change according to customer specification. The various components are filleted to give them a better outlook. 5.1.5.

Safety

A guard rail is installed around the machine to prevent any injury that may arise due to pulling in of loosely hanging clothes, hair etc. All metal edges are also blunted out to prevent cuts and bruises in case they are accidentally knocked. In addition to that, L-channels at the base allow the machine to be screwed to the ground hence preventing too much vibration.

44

5.2. ECONOMIC VIABILITY OF THE NAIL MAKING MACHINE With the objective of designing a nail making machine suitable for the cottage industry in Kenya, it is of paramount importance to get a machine which can be fabricated locally. From the available materials and manufacturing methods, we chose cheap but appropriate combinations in order to get the most economically viable design. Considerations put in place in the design and choice of materials for the various parts of the nail making machine included the type, direction and amount of force involved, machinability and castability of the part material, cost of material and fabrication, material property and aesthetics. With the above total cost of manufacture of the nail making machine, it would be affordable for the cottage industry as opposed the imported machines that come at a cost of not less than 600,000. This is due to the fact that import tax is eliminated from this. It would in turn lead to a reduction of nail prices which would improve the competition from imported nails. Mass production of this machine would further lead in the lowering of the cost of production due to the benefit of economies of scale. Having made an investment for the nail making machine, the payback period can be computed as below. The following equation can be used in the calculation:𝐼 𝑛 𝑝=0 𝑅𝑝

− 𝐷𝑝

=1

Where Rp is the income during the period p; Dp is the operating cost during the period p; n is the payback period; and I is the initial investment made in period 0.

45

Total initial investment (I) is given by; ITEM

COST

Nail making machine

95,324

Land and buildings

190,000

Vibration isolators

12,616

Wire coil stand

3,500

Weighing scale

4,000

Installation

25,000

TOTAL

330,440 Table 5.1: Total Initial investment

Operating costs (Dp) can be computed as follows: ITEM

COST

Nail wire

80,200

Packaging material

10,000

Operator

20,000

Labour

20,000

Mechanic

5,000

Security

5,000

Transport costs

30,000

Electricity

6,800

Water

700

TOTAL

177,700

Table 5.2: Operation costs

46

Cash inflow can be calculated as below: Production rating of the nail making machine innovation = 350 nails per minute. Total number of nails produced per month assuming 7 working hours per day and 20 working days per month = 350x60x7x20 = 2,940,000 nails. Number of nails in kilograms per month assuming a kg is approximately 481 nails = 6,112.3kg. Income from sale of nails produced per month assuming Kshs. 75 per kilogram = Kshs. 458,423. Cash flow is tabulated as below: Month 1

Month 2

Month 3

Month 4

Month 5

Month 6

Cash inflow (Rp)

230,000

350,000

458,423

458,423

458,423

458,423

Cash outflow (Dp)

170,200

177,700

177,700

177,700

177,700

177,700

Net cash inflow

59,800

172,300

280,723

280,723

280,723

280,723

cash 59,800

232,100

512,823

793,546

1,074,269

1,354,992

Cumulative flow

Table 5.3: Cash flow per month

From the formula above, I =

𝑛 𝑝=0 𝑅𝑝

− 𝐷𝑝

When n = 1 month, I = 337,940 ,

𝑛 𝑝=0 𝑅𝑝

− 𝐷𝑝 = 59,800 < I therefore n≠1

When n = 2 months, I = 337,940 𝑛 𝑝=0 𝑅𝑝

− 𝐷𝑝 = 232,100 < I therefore n≠2

When n = 3 months, I = 337,940 𝑛 𝑝=0 𝑅𝑝

− 𝐷𝑝 = 512,823 > I therefore n = 3

This shows that the payback period for the investment will be achieved in the third month of operation. This is therefore a worthy investment. 47

CHAPTER 6: CONCLUSION AND RECOMMENDATIONS 6.1.CONCLUSION The current design of the nail making machine has overall dimensions of 1588mm length, 635mm width and 804mm height. Focus is laid on the reduction of the bulk and overall price of the machine without compromising on the quality of the nails produced. To achieve this, the working mechanism of the nail making machine is designed so that the total number of moving parts is reduced to a necessary few. All motion of the nail making machine is conveyed from the crankshaft to the nail head punch via the connecting rod, and the nail head punch in turn drives the rest of the components, leading to a very simple yet sufficient design of the nail making. This modification aided by sufficient lubrication of the machine has also rendered the machine to be adequately air cooled without the necessity of an elaborate cooling system. Careful selection of materials is observed while considering their availability without compromising on the durability of the nail making machine once it is fabricated. On the subsequent implementation of the above design, the cottage industry will tend to develop having introduced a business opportunity. This is a blue ocean venture that will enable not only the creation of jobs within the cottage industry but will also, in line with vision 2030, boost the Kenyan economy. This would also come by way of reducing the cost of nails hence a percentage reduction of prices in the construction industry. This project is also aimed at cutting down the prices of nail making machines which are imported. By introducing this cheap and economical nail making machine into the Kenyan market, there would be competition with the imported machines and this would eventually lead to the reduction of nail prices. As is evident from the cost analysis of the nail making machine, it is much cheaper than the existing nail making machines and can be manufactured locally from the available materials. This makes it affordable for investors in the cottage industry.

48

Operation of the machine is possible under normal conditions as experienced in workshops. Good ventilation is however recommended as the machine is air cooled. Ingress of dust should be avoided by maintaining a clean working environment. This gives longer service life for the motor and eventual reduction in the cost of production. This nail making machine is found out to be economically viable as analyzed above. Its implementation has the potential of promoting the manufacturing industry in Kenya along with the creation of employment opportunities for the Kenyan people.

6.2.RECOMMENDATIONS

The nail making machine innovation can produce nails of between 2inches and 3inches. There is, however, a need for nails of other different sizes so there should be an innovation to this effect.

49

REFERENCES 1. Khurmi, R. S. (2004). A Textbook of Machine Design (14th ed., pp. 623 - 678). Eurasia Publishing House (PVT) LTD. 2. Darbyshire, A. (2008). Mechanical Engineering (2nd ed., pp. 283 – 290). Macmillan Publishers. 3. Kempster, M. H. A. (1984). Engineering Design III (1st ed., chap. 2 – 9). Macmillan India Ltd. 4. Singal, R. K. (2008). Fundamentals of Machining and Machine Tools (3rd ed., chap. 11). International Publishing House Pvt. Ltd 5. Khurmi R. S. (2004). Engineering Mechanics (19th ed., chap. 11). Rajendra Ravindra Printers (Pvt) Ltd. 6. Madara, M. O. (2004). Engineering Design (1st ed., pp. 145 - 147). Togo Press Ltd. 7. S., L. M. (2012). Advameg Inc. Retrieved from http://www.madehow.com/volume2/Nail.html 8. Maureen, K. P. (1997 - 2012). Glasglow Steel Nail Co. Ltd. Retrieved from http://www.glasglowsteelnail.com/nailmaking.html

50

APPENDICES APPENDIX 1: Cost evaluation of the Nail Making Machine COST PER NO.

ITEM

MATERIAL

QTY

Kg

Unit

TOTAL COST

1

Frame Mounting

MS

6

200

1,200

2

Frame Top length

MS

2

550

1,100

3

Frame Top width

MS

5

200

1,000

4

Frame Base length

MS

2

200

400

5

Frame Base width

MS

2

200

400

6

Crankshaft

Carbon steel

1

4,000

4,000

7

Connecting rod

MS

1

285

8

Crankshaft end lock plate

1

285

9

Bush

Bronze

10

Bearings

11

Bearing cage

12

Motor

13

Motor plate

MS

1

14

Pulley

Cast Iron

15

V-belt

-

990 100

100

2

100

200

Aluminium

2

2,000

4,000

MS

2

445

890

10,000

10,000

1,518

1,518

2

500

1,000

1

600

600

285

1

51

285

16

Flywheel

Steel

1

7,000

7,000

17

Nail head punch

Alloy steel

1

150

150

18

Nail head punch support

Carbon steel

1

7,500

7,500

19

Nail head punch cover

MS

1

285

703

703

20

Nail head punch rail

MS

1

285

1,193

1,193

21

Nail exit face plate

MS

1

285

1,951

1,951

22

Rollers

Cast Iron

6

400

2,400

23

Nail exit

Galvanized steel

1

250

250

24

Spring

Spring metal

2

300

600

25

Cam

Cast Iron

1

940

458

458

26

Cam driver

MS

1

285

728

728

27

Cutting die

Carbon steel

2

1,500

3,000

28

Cutting die lever

MS

2

285

2,584

5,168

29

Cutting die rail

MS

2

285

616

1,232

30

Cutting die rail end plate

MS

2

285

94

188

31

Cutting die roller

Alloy steel

2

300

600

32

Cutting die holder

MS

2

354

708

52

285

33

Die block

Cast Steel

1

7,477

7,477

34

Nail gripper

MS

1

30

30

35

Nail gripper driver

MS

1

285

199

199

36

Cam support

MS

1

285

330

330

37

Roller support

MS

1

285

747

747

38

Bolts and nuts

Alloy steel

20

70

1,400

39

Guard rail

MS

1

600

600

40

Nail feeder support

MS

1

2,410

2,410

41

Labor cost

15,904

42

Miscellaneous

5,000

TOTAL

285

95,324

53

APPENDIX 2: PART DRAWINGS

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

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