EVALUATION OF COOLANT CONCENTRATION ON THE MACHINIABILITY OF CARBON STEEL DURING END MILLING T. R. ANBARASAN THANGAVELU

Transcription

1 EVALUATION OF COOLANT CONCENTRATION ON THE MACHINIABILITY OF CARBON STEEL DURING END MILLING T. R. ANBARASAN THANGAVELU This project report submitted in partial fulfillment of the requirement for the Degrees of Master of Mechanical Engineering (Advanced Manufacturing Technology) Faculty of Mechanical Engineering Universiti Teknologi Malaysia June, 2007 ii

2 This thesis is dedicated to my parents, my brothers and sisters. iv

3 ACKNOWLEDGEMENT I would like to express my sincere gratitude and grateful appreciations to my supervisor, Associate Professor Dr. Safian bin Sharif, for his invaluable guidance, advice, encouragement and help throughout the project. Without his support and advice, this project would not be successfully completed. My special thanks goes to Mr. Amrifan S Mohruni for giving me guidance and support throughout the experimentation and data analysis. v

4 ABSTRACT In machining, cutting tools are used to remove unwanted material from the surface of a workpiece. This operation will transform the mechanical energy into thermal energy, generating heat at a small location. The generated heat transferred into the workpiece, the removed material, the environment and also the tool. This directly affects the tool life, the cutting performance and the quality of the products especially the surface finish. The cutting fluid is used to act as the coolant to reduce the generated heat and as lubricant to reduce the friction during the cutting process. This study explores the influence of coolant concentration on tool life, surface roughness of the product and the cutting force during end milling of mild steel S50C. High Speed Steel end mill of 4 flutes was used at various cutting conditions in the investigation. A design of experiment was planned, whereby the coolant concentration with cutting speed and feed being the factors and tool life, surface roughness and cutting forces were treated as responses. Mathematical models on the above responses were established based on the experimental results. The results of this experiment show that coolant concentration significantly affects the tool life at certain milling condition especially lower cutting speed and lower feed. At higher feed or cutting speed conditions, the coolant concentration or the coolant itself does not have any impact on the tool life. Coolant concentration does not directly affects the surface roughness but its reaction with feed does influence the results. The influence of coolant concentration on cutting force is not significant in this experimentation. vi

5 ABSTRAK Dalam pemesinan, mata alat digunakan untuk memisahkan bahan yang tidak diperlukan daripada permukaan bahan kerja. Dalam operasi ini tenaga mekanikal akan diubahbentuk ke tenaga haba, yang mana dihasilkan pada sesuatu tempat yang tertumpu. Haba yang dihasilkan akan diserap oleh bahan kerja, bahan yang dipisahkan, persekitaran dan mata alat. Ini seterusnya akan memberikan kesan terhadap jangahayat mata alat, prestasi pemotongan dan kualiti produk yang dihasilkan terutama kekasaran permukaan yang dihasilkan. Bendalir pemotong digunakan sebagai bahan pendingin yang mengurangkan haba yang dihasilkan dan juga sebagai bahan pelincir untuk mengurangkan geseran semasa proses pemotongan. Kajian ini cuba menilai pengaruh kepekatan bendalir pemotong terhadap jangkahayat mata alat, kekasaran permukaan produk dan seterusnya tenaga pemotongan semasa proses pemotongan bahan kerja mild steel S50C. Mata alat High Speed Steel dengan 4 flute digunakan dalam beberapa keadaan pemotongan dalam experimen ini. Satu rekabentuk eksperimen dirancang dimana kepekatan bendalir pemotong, kelajuan pemotongan dan suapan dijadikan faktor-faktor eksperimen, jangkahayat mata alat, kekasaran permukaan produk dan tenaga pemotongan dijadikan sebagai hasil eksperimen. Model-model matematik terhadap hasil experimen dibentuk dari keputusan yang diperolehi. Keputusan experimen menunjukkan bahawa kepekatan bendalir pemotong memberi kesan yang ketara terhadap jangkahayat mata alat pada keadaan pemotongan tertentu terutamanya apabila keadaan kelajuan pemotongan dan suapan yang rendah. Apabila kelajuan pemotongan atau suapan yang tinggi, kepekatan bendalir pemotong tidak memberi kesan terhadap jangkahayat mata alat. Kepekatan bendalir pemotong juga mempunyai reaksi dengan suapan dan memberi kesan terhadap kekasan permukaan produk. Kepekatan bendalir pemotong tidak kesan terhadad tenaga pemotongan. vii

6 TABLE OF CONTENT CHAPTER TITLE PAGE DECLARATION OF SUPERVISOR TITLE PAGE DECLARATION OF AUTHOR DEDICATION ACKNOWLEDGEMENT ABSTRACT ABSTRAK TABLE OF CONTENT LIST OF SYMBOLS LIST OF TABLES LIST OF FIGURES LIST OF APPENDICES i ii iii iv v vi vii viii xii xiii xiv xviii CHAPTER 1 INTRODUCTION Importance of study Background of study Objectives Expected results 4 viii

7 CHAPTER 2 LITERATURE REVIEW Basic Machining Theory Basic machining process Milling End milling Cutting tools Materials Machinability of carbon steel Types of Coolant and its application Effect of coolant concentration 21 CHAPTER 3 METHODOLOGY Design of experiment Parameter setting and responses Cutting tool used Work material Coolant Equipment CNC machining centre Toolmaker microscope Surface roughness measurement Coolant concentration measurement Tool wear image capturing 33 ix

8 CHAPTER 4 EXPERIMENT RESULTS AND DISCUSSION Impact of Machining conditions on Tool Wear Coolant Concentration of 5% versus 10% on 34 Tool Wear Feed of 0.05mm/tooth versus 0.15mm/tooth on 39 Tool Wear Cutting speed of 30m/min versus 100m/min on 43 Tool Wear DOE analysis on Tool life (V B = 0.02mm) Impact of Machining conditions on Surface 53 Roughness Coolant Concentration of 5% versus 10% on 53 Surface roughness Feed of 0.05mm/tooth versus 0.15mm/tooth on 54 Surface roughness Cutting speed of 30m/min versus 100m/min on 55 Surface roughness DOE analysis on Surface roughness Impact of Machining conditions on Cutting Force Coolant Concentration of 5% versus 10% on 61 Cutting Force Feed of 0.05mm/tooth versus 0.15mm/tooth on 62 Cutting Force x

9 4.3.3 Cutting speed of 30m/min versus 100m/min on 63 Cutting Force DOE analysis on Cutting Force 64 CHAPTER 5 CONCLUSION 69 REFERENCES 71 APPENDICES 73 xi

10 LIST OF SYMBOLS MQL - Minimum Quantity Lubricant f CS CC - feed (mm/tooth) - Cutting speed (m/min) - Coolant concentration DOE - Design of Experiment V B CH - Tool wear - Chipping µch - Micro chipping C HSS TiN - Carbon - High speed steel - Coated with Titanium Nitrate TiCN - Titanium Carbonitride TiAlN - Titanium Aluminium Nitrite TiAlCrN - Titanium Aluminium Cromium Nitrite PVD PCB PCD - Physical Vapour Deposition Printed Circuit Board - Polycrystalline diamond ASTM - American Society for Testing and Materials AISI JIS -The American Iron and Steel Institute Japanese Industrial Standards xii

11 LIST OF TABLES Table Title Page Table 3.1 DOE experiment plan 24 Table 3.2 Chemical composition of work material S50C 25 Table 3.3 Physical properties of work material S50C 26 Table 3.4 Typical Physical & Chemical Characteristics 27 Table 3.5 Specification of the CNC machining Center MH 700s 29 Table 3.6 Toolmaker microscope equipment specification 30 Table 3.7 Taylor-Hobson Surface Roughness Tester equipment 31 specification Table 4.1 Tool life for CC of 5% and 10% at various cutting condition 37 Table 4.2 Tool life for feed of 0.05mm/tooth and 0.15mm/tooth at various 42 cutting condition Table 4.3 Tool life for CS 30m/mim and 100m/min at various cutting 46 condition xiii

12 LIST OF FIGURES Figure Title Page Fig.2.1 Basic cutting mechanism 6 Fig.2.2 Machining and Chip formation 6 Fig 2.3 Machining processes 7 Fig 2.4 Milling processes 8 Fig 2.5 End milling 9 Fig 2.6 Vertical milling Machines 10 Fig 2.7 critical factor of End Milling 11 Fig 2.8 Specific purpose end mills 12 Fig 2.9 : 2 common classification of ferrous alloys by structure and 16 commercial name or application Fig 2.10 Coolant applications 19 Fig 3.1 Input and output variables of process 22 Fig 3.2 Cutting tool side and top view 25 Fig 3.3 Milling system 28 Fig 3.4 Toolmaker microscope 30 Fig 3.5 Taylor-Hobson Surface Roughness Tester 31 Fig 3.6 The principles of refractometers 32 Fig 3.7 Hand Refractometer N-20E 33 xiv

13 Fig 3.8 Zeiss Video Microscope 33 Fig 4.1 Tool wear at 5% coolant concentration 34 Fig 4.2 Tool wear at 10% coolant concentration 35 Fig 4.3 Pictures of failed tools, A chipping, B Microchip, 35 C- normal wear Fig 4.4 Tool wear at for CC of 5% and 10% for low CS and low feed 36 Fig 4.5 Tool wear at for CC of 5% and 10% for high CS and high feed 36 Fig 4.6 Tool life for CC of 5% and 10% at various cutting condition 37 Fig 4.7 Tool wear at for CC of 5% and 10% at various cutting condition. 38 Fig 4.8 Tool wear at for CC of 5% and 10% at various cutting condition. 38 Fig 4.9 Tool wear at for feed of 0.05mm/tooth vs. 0.15mm/tooth 39 (CC 5%, CS 30). Fig 4.10 Tool wear at for feed of 0.05mm/tooth vs. 0.15mm/tooth 39 (CC 10%, CS 30). Fig 4.11 Tool life for Feed of 0.05mm/tooth vs. 0.15mm/tooth 40 (CC 5%, CS 100). Fig 4.12 Tool life for Feed of 0.05mm/tooth vs. 0.15mm/tooth 41 (CC 10%, CS 100). Fig 4.13 Tool life for feed of 0.05mm/tooth and 0.15mm/tooth at 41 various cutting condition. Fig 4.14 Tool life for CS 30m/mim and 100m/min 43 (at CC5%, feed 0.05mm/tooth). Fig 4.15 Tool life for CS 30m/mim and 100m/min 43 xv

14 (at CC 10%, feed 0.05mm/tooth). Fig 4.16 Tool life for CS 30m/mim and 100m/min 44 (at CC 5%, Feed 0.15mm/tooth). Fig 4.17 Tool life for CS 30m/mim and 100m/min 45 (at CC10%, feed 0.15mm/tooth). Fig 4.18 Tool life for CS 30m/mim and 100m/min at various 45 cutting condition. Fig 4.19 DOE for tool life results 47 Fig 4.20 Pareto chart of the standardized effects 48 Fig 4.21 Normal probability plot of the standardized effects 49 Fig 4.22 Main effects plot 49 Fig way and 3 way interactions 50 Fig way and 3 way interactions graph 50 Fig 4.25 Estimated coefficients for tool life mathematical model 51 Fig 4.26 Response optimizer for Tool life 51 Fig 4.27 Surface roughness at conditions coolant concentration 53 5% and 10% Fig 4.28 Surface roughness at conditions feed 0.05mm/tooth and mm/tooth Fig 4.29 Surface roughness at conditions cutting speed 30m/min 55 and 100m/min Fig 4.30 Significant factors affecting the Surface roughness 56 Fig 4.31 Pareto chart of the standardized effects 57 xvi

15 Fig 4.32 Normal Probability Plot of the standardized effects 57 Fig 4.33 Main Effects plot for Surface roughness 58 Fig way and 3 way interactions between factors for Surface 59 roughness Fig 4.35 Interactions plot between factors for surface roughness 59 Fig 4.36 Estimated coefficients for surface roughness formula 60 Fig 4.37 Response optimizer for surface roughness 60 Fig 4.38 : Cutting force at conditions coolant concentration 5% 61 and 10% Fig 4.39 Cutting Force at conditions feed 0.05mm/tooth and mm/tooth Fig 4.40 Surface roughness at conditions cutting speed 30m/min 63 and 100m/min Fig 4.41 Significant factors affecting the Cutting force 64 Fig 4.42 Pareto chart of the standardized effects 64 Fig 4.43 Normal Probability Plot of the standardized effects 65 Fig 4.44 Main Effects plot for Cutting Force 66 Fig 4.45 Interactions between factors for cutting force 66 Fig 4.46 Interactions plot between factors for cutting force 67 Fig 4.47 Estimated coefficients for surface roughness formula 67 Fig 4.48 Response optimizer for Cutting Force 68 Fig 4.49 Response optimizer for all responses 70 xvii

16 LIST OF APPENDICES Appendix Title Page Appendix 1 Experiment results for Tool Wear 74 Appendix 2 Experiment results for Surface roughness 77 Appendix 3 Experiment results for Cutting force 80 Appendix 4 Tool Before cut 83 Appendix 5 Tool #1 CS 30, Feed 0.05, CC 5% 84 Appendix 6 Tool #2 CS 100, Feed 0.05, CC 5% 86 Appendix 7 Tool #3 CS 30, Feed 0. 15, CC 5% 87 Appendix 8 Tool #4 CS 100, Feed 0.15, CC 5% 88 Appendix 9 Tool #5 CS 30, Feed 0.05, CC 10% 89 Appendix 10 Tool #6 CS 100, Feed 0.05, CC 10% 90 Appendix 11 Tool #7 CS 30, Feed 0.15, CC 10% 91 Appendix 12 Tool #8 CS 100, Feed 0.15, CC 10% 92 Appendix 13 Tool #9 CS 65, Feed 0.10, CC Appendix 14 Tool #10 - CS 65, Feed 0.10, CC Appendix 15 Tool #11 - CS 65, Feed 0.10, CC Appendix 16 Tool #12 - CS 65, Feed 0.10, CC Appendix 17 Tool #13 CS 30, Feed 0.05, CC Dry 97 Appendix 18 Tool #14 CS 30, Feed 0.05, CC Dry 98 xviii

17 xix

18 CHAPTER 1 INTRODUCTION 1.1 Importance of study A recent survey on world output of machine tools by 28 major producing countries shows that these countries produced $51.8 billion US dollars worth of machine tools in 2005 [1]. A machine tool here is defined as a powerdriven machine, powered by an external source of energy. The machine tool is designed specifically for metalworking either for cutting, forming, physicochemical processing, or a combination of these techniques [1]. This shows how vast is metalworking industries, furthermore this statistics covers only the industries that are directly involved in producing machine tools. There are numerous other industries that are related directly and indirectly which are worth huge magnitude in dollar values and have significant affect towards the global economics. Today, almost all industries one way or another related and dependant on metalworking. The metalworking varies from extraction of precious metals to make jewelry, building more efficient electronics, and for industrial and technological applications from construction to shipping containers to rail, and air transport. Without metalworking, goods and services would cease to move around the globe. Machining is a major part of metalworking that plays important role in metal cutting and forming. In machining, the machine tools especially cutting tools play an important role. This is because of their roles in producing shapes and forms. Their importance is not only in technical aspects but financial too due to 1

19 their cost. Their performance and tool life is very much an important criteria to every cost conscious management. This study involved the analyzing of the important factors that contribute to the efficiency of cutting tool during end milling of carbon steel using High Speed Steel (HSS) tool. Improving the efficiency of the machining performance and the quality of product produced was explored. 1.2 Background of study In machining, cutting tools are used to remove material from the surface of a less resistant body of a work-piece. Though the geometry of cutting tools varies from each type of metal removing process, the basic fundamentals are the same. Through relative movement and application of force the removal process takes place. This operation will transform the mechanical energy into thermal energy, generating heat at small location which will affect the tool life, the cutting performance and the quality of the product. Cooling of this area is very critical in machining to have longer tool life and improve product quality. Here, end milling is chosen as the area of study to determine the impact of process parameters and cutting fluid concentration on the performance of a cutting tool as well as the surface roughness and the cutting force. The tool life performance of the cutting tool is determined through the wear of cutting edge. The wear is a product of the material properties of tool such as wear resistance and the adverse impact of the cutting operation itself. During cutting process, the tool is subjected to load, friction and high temperature. Adhesion, abrasion, diffusion, oxidation and fatigue during the cutting operation will cause tool to wear. 2

20 The cutting fluid is used to act as the coolant to reduce the generated heat between the workpiece and tool and also as the lubrication agent to reduce the friction at the tool-chip interface. The correct selection of cutting fluid and the optimum concentration have a great impact on the overall performance of the cutting tool. Cutting fluid concentration has impact on causing too much foaming, rusting of workpiece and poor tool life. N. R. Dhar et. al. [2], investigated the effect of Minimum Quantity Lubricant (MQL) on temperature, tool wear and product quality in turning AISI 9310 steel. They concluded that MQL was better than dry cutting as it reduced cutting temperature and produced better surface finish and dimension accuracy. In another study also by N.R. Dhar et. al., [3] on the effects of cryogenic cooling on temperature, tool wear, surface roughness and dimensional deviation in turning AISI 8740 steel by coated carbides, indicated that the cryogenic cooling by liquid nitrogen jets provided lesser tool wear, better surface finish and higher dimensional accuracy as compared to dry and wet or the conventional flood machining. The above studies [2,3] are the examples of today s trend moving away from conventional flood or wet machining. One of the arguments put forward on conventional wet machining is that it fails to penetrate into the chip-tool interface, thus cannot remove the heat effectively. The reason behind is that the addition of extreme pressure additives in cutting fluids does not ensure penetration on the coolant. It is also claimed that cutting fluid is costly and causing serious threat to the environment due to its complex chemical compositions. There may some truth in all these claims but in wet machining, an area is seriously overlooked in these studies is the correct type and optimum concentration of cutting fluid. This area has a lot of potential as the cutting fluid industries grow rapidly and producing better environmentally friendly and better performance cutting fluids. 3

21 This study is not venturing on which is the better method cooling for machining but rather concentrate on better machining performance could be achieved if optimum concentration is used. 1.3 Objectives This study involves the establishment of design of experiment (DOE) plan with 3 factor 2 level factorial design, whereby the input variables are the feed (f), cutting speed (CS) and the coolant concentration (CC) during end milling process of medium carbon steel using High Speed Steel (HSS) tool. The output variables are tool wear, the surface roughness of the workpiece and the cutting force. The main objectives of this study are: i to establish the relationship between coolant concentration with the tool wear, surface roughness and cutting force during end milling carbon steel. ii to determine the optimum condition of coolant concentration and machining parameters for tool life and surface finish. iii to establish mathematical models for cutting force, surface roughness and tool life when end milling carbon steel 1.4 Expected results Higher feed and cutting speed should increase the tool wear. This is expected as more mechanical energy is transformed into thermal energy thus causing adverse effect on the cutting tools. Reducing the generated heat during cutting can extend the tool life. Increase in coolant concentration may improve the performance of the tool and should plateau at certain concentration as additional increase in concentration may not improve the tool performance. This is probably due to coolants are designed to perform best at specific concentration. Overly diluted coolant may reduce tool life as its function as lubricant will not be effective, and too much concentrated coolant results in using more coolant than necessary which will be a waste to the process. 4

22 CHAPTER 2 LITERATURE REVIEW 2.1 Basic machining theory The major development of machining started in 1760s when large metal cylinders and other high accuracy parts were required for building the steam engines. After more than a century, in mid 1880s, the focus and effort in manufacturing has started to shift from developing basic machine tools and producing highly accurate parts to reducing machining costs and cutting new types of metals and alloys [4]. Today, the mechatronics age, integrated manufacturing systems is far more advanced in metal cutting technology is taking over the individual, stand along conventional machining which as used since the turn of the century. Also today there are many new alloys have been developed to meet the increasing demand required for better material characteristics to perform under severe conditions with stress, temperature and corrosion. The machining processes are also pushed to cope up with demanding changes to produce better and accurate products. This has developed machining technology tremendously, however the basics remain the same. Fundamentally, machining involves a metal cutting tool, which takes a form of a large angled wedge, which is driven asymmetrically into the work material, to remove a thin layer from a thicker work material body [5] as shown in Fig 2.1, 5

23 Thin layer removed The cutting tool High temperature Work material Fig.2.1 Basic cutting mechanism In spite of the diversity of the geometry of machining operations, the basic mechanism of chip formation is essentially the same for all cutting processes, such as turning, drilling, milling or thread cutting. The layer that is being removed must be thin to enable the tool and work to withstand the imposed stress. The material is removed in the form of chips. The chips are produced by the cutting tool which moves along the workpiece with a relative velocity and with a depth of the cut. The tool shears the chip along a shear plane. The chip thickness is related to the rake angle and the shear plane angle, as shown in Fig 2.2 Fig.2.2 Machining and Chip formation 6

24 2.2 Basic machining process Most machining operations can be grouped as processes, which remove metal from a material. Machining operations involve power driven machine tool to shape metal as required. Turning, milling, grinding and drilling are some of the conventional machining processes. There are new non-conventional machining processes which are advanced using electrical discharge, electro chemical erosion as laser cutting to shape metal work pieces. These advanced machining processes will not be discussed in this study. The traditional machining processes are grouped into various ways but here they are grouped into two groups, which are cutting and grinding. Cutting generally involves single point cutting or multipoint cutting tools whereas the grinding is considered as abrasive process. The breakdown of the machining processes are shown in Fig 2.3 Traditional Machining Cutting Abrasive cylindrical shape Various shapes Bonded Loose Turning Milling Grinding Abresive jet machining Drilling Planning Shapping Fig 2.3 Machining processes 7

25 2.3 Milling Milling is used to machine components requiring intricate geometries. Depending on the machining requirements, different milling configurations; such as slab milling, face milling, and end milling, can be utilized ( Fig 2.4). Fig 2.4 Milling processes In peripheral milling or slab milling, the cutting tool has teeth located on the periphery of the cutter body. The axis of cutter rotation is generally in a plane parallel to the work-piece surface to be machined. In face milling the cutting tool is on a spindle working perpendicular to the workpiece during the cutting. The milled surface is located on the periphery and face of the cutter. Whereas for the end milling, the cutting tool rotate vertically with the work piece. The cutting teeth are located on both the end face and the periphery of the cutter body [5]. 8

26 2.4 End milling In end milling, the cutter rotates with a fixed speed, while the workpiece is moved. The end milling is one of common and frequently used metal cutting form. Fig 2.5 represents the basic end milling process. Fig 2.5 End milling Generally, the column - and - knee type machines are extensively used for most milling operations. For end milling, a vertical - spindle column - and - knee type machine is used. The primary components of this machine are the worktable, saddle, knee, and head. The workpiece to be machined is attached to the worktable, which moves horizontally (left and right). In turn, the worktable is supported by the saddle, which also moves horizontally (in and out). The vertical movement of the table (up and down) is controlled by the knee. This component 9

27 allows the user to change the depth of cut. Finally, the head houses the spindle and different cutters. Fig 2.6 Vertical milling machines The basic components of a vertical milling machines (Fig 2.6) include in are as follows: Work table, on which the workpiece is clamped using the T-slots. The table moves longitudinally with respect to the saddle. Saddle, which supports the table and can move transversely. Knee, which supports the saddle and gives the table vertical movements for adjusting the depth of cut. Overarm in horizontal machines, which is adjustable to accommodate different arbor lengths. Head, which contains the spindle and cutter holders. In vertical machines the head may be fixed or vertically adjustable. The critical factors such as the rotating speed, the sending speed or feed and depth of cut that effect the whole cutting process are listed in Fig

28 Fig 2.7 Critical factor of end milling The rotating speed, the cutting depth and sending speed are very important and they are affected by the materials, the shapes and the roughness of the surface and etc. Generally, in order to get the low roughness, the cutting depth must be set to small, and the sending speed must be set to low. 2.5 Cutting tools The cutting tools vary based on the specific purpose of cutting preference. The various types of end mill are given below: Solid End Mill Ball End Mill Tapered End Mill Roughing End Mill Shell End Mill Fig 2.8 illustrates some of the end milling operates in the metal cutting industries. 11

29 Fig 2.8 Various types of end milling operations Solid end mills are the most generic type of milling cutter and they are suitable for light and medium cutting. The end of the solid end mill is perpendicular to the axis of the cutter. The solid end mill has either two or four flutes though it is possible to have more. Number of flutes on a milling cutter strongly influences the cutter s usage. Ball end mill has a hemispherical end. The radius of the hemispherical end and end mill body are equal. Half round channels can be easily machined by ball end mills. Ball end mills are also used for die making to make complex internal curves. Usually, ball end mills are solid and two fluted. Tapered end mill is similar to a standard end mill except that the tool itself is tapered (thicker at the top than at the bottom). It s also used for die making when a specific angle edge cut is custom. Roughing end mills are used for 12

30 roughing, or removing greater amount of metals quickly. It is similar to a standard end mill that has threaded cutting edges. Normally these types of mills have four flutes. Shell end mills look like solid end mills with only the shell and center removed. Shell end mills are larger than solid end mills and suitable for larger work piece. It gives a clear finish with less chatter. [5] End mill tools are traditionally been made from high speed steel, but are now mostly made of tungsten carbide, a rigid and wear-resistant material, usually pressed from carbide powder into rods, which are then ground into blanks of industry-standard sizes. There are a variety of end mill tools being made and used nowadays. High carbon steel tools are made from high carbon steel, an improvement on plain carbon steel due to the hardening and tempering capabilities of the material. These tools can be used on wood or metal, however they have a low tolerance to excessive heat which causes them to lose their strength, resulting in a soft cutting edge. High speed steel (HSS) is a form of tool steel where the material is much more resistant to heat. They can be used for drilling of metal, hardwood, and most other materials at greater cutting speed than high carbon steel tools and have largely replaced them in commercial applications. Cobalt steel alloys are variations on high speed steel which contain more cobalt in them. Their main advantage is that they hold their hardness at much higher temperatures, as such they are used for drilling stainless steel and other hard materials. The main disadvantage of cobalt steels is that they are more brittle than standard HSS. In the early 1990's, use of coatings to reduce wear and friction (among other things) became more common. Most of these coatings are referred to by their chemical composition, such as: TiN (Coated with Titanium Nitrate) 13

31 TiCN(Titanium Carbonitride), TiAlN (Titanium Aluminium Nitrite), and TiAlCrN (Titanium Aluminium Cromium Nitrite),. Titanium nitride is a very hard ceramic material, and when used to coat a HSS tool, can extend the cutting life by three or more times. A titanium nitride drill cannot properly be sharpened, as the new edge will not have the coating, and will not have any of the benefits the coating provided. TiAlN is another coating which is frequently used lately. It is considered superior to TiN. Advances in end mill coatings are being made, however, with coatings such as amorphous diamond and nanocomposite PVD coatings beginning to be seen at high-end shops Tungsten carbide is extremely hard, and can drill in virtually all materials while holding an edge longer than other bits. However, due to its high cost and brittleness, it is more frequently used only in smaller pieces screwed or brazed onto the tip of the bit. It is becoming common in job shops to use solid carbide drills, and in certain industries, most notably PCB drills, it has been common place for a long time. Polycrystalline diamond (PCD) is among the hardest of all tool materials and is therefore extremely wear resistant. The material consists of a layer of diamond particles, typically about 0.5 mm thick, bonded as a sintered mass to a tungsten carbide support. Bits are fabricated using this material by brazing small segments to the tip of the tool to form the cutting edges. These bits are typically used in the automotive, aerospace, and other industries to drill abrasive aluminum alloys, carbon fiber reinforced plastics and other abrasive materials. Diamond powder is used as an abrasive, most often for cutting tile, stone, and other very hard materials. Large amounts of heat are generated, and diamond coated drills often have to be water cooled to prevent damage to the bit or the workpiece. 14

32 2.6 Materials Steels can be classified by a variety of different system depending on the composition such as carbon, low alloy or stainless steel; the finishing method such as hot rolling, cold rolling; the microstructure such as ferrite, pearlitic and martensitic; the required strength level as specified in ASTM standards; the based on the heat treatment process such as annealing, quenching and tempering and thermo-mechanical processing and many more. The Fig 2.9 shows 2 common classifications of ferrous alloys by structure and commercial name or application. Carbon steel is a metal alloy containing 2 major elements, iron and carbon and other elements are present in very small quantities. The American Iron and Steel Institute (AISI) defines carbon steel as follows steel is considered carbon steel when no minimum content is specified or required for Chromium, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium as any other element to be added to obtain a desired alloying effect or does not exceed the maximum content for manganese (1.6%), silicon (0.6%), and copper (0.6%). Carbon steel is considered as the most frequently used steels. More than 85% of the steel produced and shipped in the United States is carbon Steel. The carbon content determines the 3 major groups of carbon steels, low carbon, medium carbon and high carbon. The largest category of this group is the low carbon steel, which contains up to 0.3% carbon. The typical usage is automobile body parts, the plate and wire products. Also used for stampings, forgings, seamless tubes and boiler parts. The ductility of low carbon steel can be easily manipulated for the usage like automobile body parts. 15

33 Fig 2.9 : 2 common classification of ferrous alloys by structure and commercial name or application. 16

34 The medium carbon steel is as similar as the low carbon steel except the carbon content ranges from 0.3% to 0.6% and the manganese content from 0.6% to 1.65%. This steel has higher tensile strength and low ductility than the low carbon steel. The application for this type of carbon steel includes farm equipment, engine components, gears and structural fixtures. These components needs to be very strong and durable yet not brittle. The medium carbon steel meets this requirement. The medium carbon steel is also will hold up many cycles of stress and strain such as in the engine parts enduring a lot of loading and unloading. Brittle materials will not be able to withstand this and result in mechanical failures overtime. Material that is too soft will result in extreme elongation if subjected to high temperature. The higher the carbon content, the lower the elongation at high temperatures. The high carbon steel contains 0.6% to 1.00% with manganese content ranging from 0.3% to 0.9%. High carbon steels are used for spring material and high strength wires. This steel is with best hardness, strength and least ductility. The application for this type of steel is in tools, drills saws knife blades and bearings. Ultra high carbon steel is experimental alloys containing 1.25% to 2.0% carbon. More than 2 % carbon content, the alloy will be considered cast iron. 2.7 Machinability of carbon steel The characteristics of steel such as hardness, chemistry, microstructure, mechanical state and hardening characteristics affect the machinability of the material. For example the machinability of most of the materials decreases with increasing hardness. By increasing the hardness, the cutting forces are increased and the high temperatures and stresses lead to plastic collapse of the cutting edge. Thus affecting the tool efficiency. 17

35 The low carbon steels are with very low level of carbon and very ductile, they tend to adhere to the tool during the machining. This increases the difficulty of breaking chips and results in build up edge formation, which in turn will lead to poor surface finishing. The medium carbon steels are harder than the low carbon steels. They tend to yield higher cutting forces, as a result the medium carbon steels are machined at lower cutting speeds than the low carbon steels. Speed should be progressively decreased as the carbon content is increased. There is also less chip breaking difficulties and build up edge formations on medium carbon steel compared to low carbon steel. High carbon steels contain a higher content of carbon which makes them harder than the low or medium carbon steel. The cutting speed and feed rates are lower for high carbon steel. [6] 2.8 Types of coolant and its application Almost all machining processes produce heat and friction which will potentially damage the cutting tools as well as the surface finish of the product. To reduce the friction, transfer the heat and to remove metal particles away from the cutting zone normally cutting fluids are used. Heat formation in machining involves two important processes, firstly generation of heat during the deformation of the metal by the tool and secondly friction during the movement of chips between the work-piece and the cutting tool. 18

36 It is very important to provide cutting fluids to reduce the friction and remove heat as rapidly as possible. There are basically 3 types of cooling or lubrication applications practiced by the industries nowadays. They are; 1) Flood/wet cooling A common type of cooling where by the whole work piece and cutting tool are flooded with cutting fluid using pipes, hose and nozzle. 2) Minimal Quantities Lubricant Cutting fluid is atomized by a jet of air and the mist is directed at the cutting zone. 3) Cryogenic cooling Highly pressurized nitrogen gas blown on cutting area. There is also dry cutting practiced by certain industries where no coolant is used for metal cutting processes. Fig 2.10 shows schematic views of the different applications of cutting fluid during machining. Fig 2.10 Coolant applications 19

37 Practically all cutting fluids presently in use fall into one of four categories: Straight oils Soluble oils Semi-synthetic fluids Synthetic fluids Straight oils are non-emulsifiable and are used in machining operations in an undiluted form. They are composed of a base mineral or petroleum oil and often contains lubricants such as fats, vegetable oils and esters as well as additives such as Chlorine, Sulphur and Phosphorus. Straight oils provide the best lubrication and the poorest cooling characteristics among cutting fluids. Soluble oil fluids form an emulsion when mixed with water. The concentrate consists of a base mineral oil and emulsifiers to help produce a stable emulsion. They are used in a diluted form (usual concentration = 3 to 10%) and provide good lubrication and heat transfer performance. They are widely used in industry and are the least expensive among all cutting fluids. Semi-synthetic fluids are essentially combination of synthetic and soluble oil fluids and have characteristics common to both types. The cost and heat transfer performance of semi-synthetic fluids lay between those of synthetic and soluble oil fluids Synthetic fluids contain no petroleum or mineral oil base and instead are formulated from alkaline inorganic and organic compounds along with additives for corrosion inhibition. They are generally used in a diluted form (usual concentration = 3 to 10%). Synthetic fluids often provide the best cooling performance among all cutting fluids [7]. 20

38 2.9 Effect of coolant concentration There are a various reasons on why the cutting fluids are used in metal machining, majority is for as improving the tool life, reducing work-piece thermal deformation, improving surface finish and flushing away chips from the cutting zone. The correct type of coolant and correct concentration is very critical to the performance of the cutting process. Ezugwu et al [8] had a study made on the effect of coolant concentration on the machinability of nickel-base Nimonic C263 alloy. The study involved the use of triple coated carbide insert at various coolant concentration and under various cutting speed. Analysis of the recorded data shows that tool performance during machining is dependent on coolant concentration. they found that 6% coolant concentration gave the best overall performance as effective combination of cooling and lubrication functions during machining. 21

39 CHAPTER 3 METHODOLOGY 3.1 Design of experiment An experimental design involves making purposeful changes of the inputs (factors) to a process (or product) in order to observe the corresponding changes in the outputs (responses). Fig 3.1 illustrates the fundamental concepts. Normally the objectives of Design of Experiments (DOE) will be 1) To determine which factors have an influential effect on the response 2) To determine the appropriate settings of the influential factors for optimization of the response 3) To determine the appropriate settings of the influential factors for minimization of the response s variability 4) To determine the appropriate settings of the influential factors for maximization of the response s robustness versus the noise factors Fig 3.1 : Input and output variables of process 22

40 Factorial designs allow for the simultaneous study of 2 or more treatment factors. Performing an experiment, by varying the levels of the factors simultaneously rather than one at a time, is efficient in terms of time and cost. It also allows for the study of interactions between the factors. Interactions are often the driving force in the process. Without the use of factorial experiments, important interactions may remain undetected. A two level by three factors, full factorial design was planned for this study on the effects of coolant concentration on the machinability of carbon steel during end milling. The input variables or the factors for this design plan are the feed and cutting speed and the coolant concentration. The output variables or the responses will be the tool life, surface roughness of the machined part and the cutting force. The minimum number of runs for 1 replication will be 8 runs. 4 center point runs are added to the experiments which resulted in 12 minimum runs or treatments are carried out in this study. The experiment plan is shown in Table Parameter setting and responses The parameter settings are Feed :- 0.05mm/tooth as low level and 0.15mm/tooth as the high level Cutting speed :- 30m/min as the low level and the 100m/min as the high level Coolant concentration :- 5% as the low level and 10% as the high level. 23

41 Table 3.1 DOE experiment plan StdOrder RunOrder CenterPt Blocks Feedrate Cutting Speed Coolant Concen Cutting tool Used The constant factors for the experiment are the end mill which specified as High Speed Steel, 4 flute, 10mm diameter, Helix Angle = 30 o and Rake Angle = 10 o Fig 3.2 shows the cutting tool top and side view. 24

42 Fig 3.2 Side and top view of the end mill 3.4 Work Material The work piece used is AISI 1148, JIS S50C, Medium carbon steel, 30mm X 10mm X 5mm for the end milling experiment and 15mm X 10mm X 5mm block for the cutting force experiment. This medium carbon steel has good machinability and mechanical strength. The general application of this material is punch holders, die holders, guide plates, backing plates jigs and fixtures. Tables 3.2 and 3.3 shows the chemical composition and physical properties of the work material. Table 3.2 Chemical composition of work material S50C C Fe Mn Si S50C 0.5% 98.5% 0.7% 0.3% 25

43 Table 3.3 Physical properties of work material S50C Density 7.75g/cc Hardness, Rockwell C 58 Hardness after tempering at 200 C Hardness, Brinell 210 Tensile strength, Ultimate 650 mpa Tensile strength, Yield 340 mpa Elongation at Break 20% Reduction at Break 40% Modulus of elasticity Modulus of elasticity at elevated Temp 195 GPa 177 GPa 3.5 Coolant The coolant used is ECO COOL 68 CF2 a low-mineral oil, watermiscible coolant designed for multi-purpose use on cast iron, steel and nonferrous materials. Ecocool 68 CF 2 produces a long-life, stable and finely dispersed beige opalescent emulsion when mixed with water. Ecocool 68 CF 2 is free of nitrite and PTBBA(4-tert-Butylbenzoic acid) and contains no substances designated as hazardous. The benefits of using Ecocool 68 CF 2 includes - High emulsion stability - Good cooling and lubrication - Excellent Tool life - Outstanding detergency - Excellent corrosion protection - Low foaming tendency 26

44 Ecocool 68 CF 2 recommended concentrations as below; - Normal machining operation - 3-5% - Difficult machining operations - up to 10% - Grinding - 2-3% The typical physical & chemical characteristics of EcoCool 68 CF 2 are listed in Table 3.4. Table 3.4 Typical Physical & Chemical Characteristics Properties Unit Value Norm Test Density at 15 C Kg/l ASTM D 1298 Color 1.5 ASTM D 1500 Viscosity at 20 C mm²/s 210 ASTM D 445 Viscosity at 40 C mm²/s 65 ASTM D 445 ph-value of the emulsion / DIN water / 10% 9.4 DIN ph-value of the emulsion / DIN water / 5% 9.3 DIN Corrosion Test (chip/filter test) / 5% 0-0 IP 287 Foam Test (water hardness 3 d) / 5% minutes 3 AFNOR D Foam Test (water hardness 15 d) / 5% minutes 300/190 AFNOR D Reserve Alkalinity up to ph = 7 ml 0.1 n 175 FLP* HCl Reichert wear test / DIN water / 5% mm² 27.7 FLP* Refractometer / Fluid Tester factor 1.05 FLP* 27

45 3.6 Equipment CNC machining centre End milling tests were carried out on a MAHO MH 700 S CNC machining centre as shown in Fig 3.3. The machine specification is shown in Table 3.5 Fig 3.3 Milling system 28

46 Table 3.5 : Specification of the CNC machining Center MH 700s Description Technical Data 1) Working Range A long horizontal longitudinal axis (X axis) 700mm A long vertical axis, headstock traverse (Y axis) 500mm Horizontal traverse axis (Z axis) 600mm A axis ± 20º B axis ± 360º Maximum table load Carrying capacity, approx 100 kg 2) Work spindles Tool Mounting Clamping force of tool clamping device, ISO Type B clamping journal 3) Spindle speed and feed rates Work spindle speed, directly programmable Correcting of directly programmable speed (override) Feed rates directly programmable along X, Y and Z axes Rapid traverse a long X, Y and Z axes Reduced feed and rapid traverse rates (override) along X, Y and Z axes 4) Tool changer with disk magazine Number of Machine stations Tool diameter max All stations occupied Maximum tool diameter with Automatic double changer working Maximum tool length (from spindle speed) Tool weight, maximum Compressed air connection, approx. 5) Electrical Equipment Voltage Frequency Total connected load of machine with cooling lubricant system 600 liters 6) Weights and Space requirements Weight of machine (including vertical milling head, circular table, tool changer, cabin and switch cabinet) Approx Machine dimension Length Width Height ISO kN rpm % m/min 10 n/min % mm 100 mm 80 mm 315 mm 10 kg 6 7 bar 220 / 380 V 50 / 60 V 36.0 k VA 5950 kg 4034 mm 5550 mm 2475 mm 29

47 3.6.2 Toolmaker microscope A toolmaker microscope (Fig 3.4) was used to measure the tool wear after every interval after every observation point of the run. The machine specification is listed in Table 3.5 Fig 3.4 Toolmaker microscope Table 3.6 Toolmaker microscope equipment specification Brand Manufacture Voltage : Nikon : Japan : 100V 120V/1A 220V 240V/0.5A Working Range : X axis - 52 mm Y Axis 52 mm Lens : Magnification 10X 30

48 3.6.3 Surface roughness measurement The surface roughness after end milling was measured using a Taylor- Hobson Surface Roughness Tester (Fig 3.5). This tester combines advanced technology with high precision and value for efficient measurement of surface finish in the workshop, inspection room or laboratory. The instrument is usable handheld on horizontal, vertical and inclined surfaces or bench mounted with accessories for batch measurement or laboratory applications. The pick-up holder is mounted on a slide for vertical adjustment and can also be rotated to different measuring positions, including right-angled measurement. Table 3.7 shows the equipment specification. Fig 3.5 Taylor-Hobson Surface Roughness Tester Table 3.7 Taylor-Hobson Surface Roughness Tester equipment specification Model : Surtronic 3+ Manufacture Lc : UK : 0.25mm, 0.8mm & 2.5mm Accuracy : 0.01 µm 31

49 3.6.4 Coolant concentration measurement The coolant concentration was measure using a hand refractometer model ATAGO N- 20E. The principles of refractometer are summarized in Figure 3.6. The detection is done by utilizing the refractive phenomenon produced on the boundary of the prism and sample. The refractive index of the prism is much larger than that of the sample. If the sample is thin, the angle of refraction is large see line "A" because of the large difference in refractive index between the prism and the sample. If the sample is thick, the angle of refraction is small seeing line "B" because of the small difference in refractive index between the prism and the sample. The hand held refractomer used is shown in Fig 3.7 Fig 3.6 The principles of refractometer 32

50 Fig 3.7 Hand refractometer N-20E Tool wear image capturing Zeiss Video Microscope(Fig 3.8) was used to observe and capture the image of the tool wear at high magnification. Fig 3.8 Zeiss Video Microscope 33

51 CHAPTER 4 EXPERIMENT RESULTS AND DISCUSSION 4.1 Influence of machining conditions on tool wear Coolant concentration of 5% versus 10% on tool wear Fig 4.1 Tool wear at 5% coolant concentration Figure 4.1 shows the graphical relationships of tool wear against cutting time at various coolant concentrations and cutting speed. The actual experiment results for tool wear is available in Appendix 1. At low coolant concentration, failure mode of chipping (Fig 4,.3) occurs at the cutting condition of high cutting speed/low feed and the low cutting speed/high feed combinations before it reaches the average 0.2mm tool wear criteria. This phenomenon is reduced with higher coolant concentration (Fig 4.2) whereby no chipping was observed at low cutting speed/high feed combinations and only microchip was observed for high cutting speed/low feed combination, this microchip was observed when tool wear reached the 0.2mm criteria. 34

52 Fig 4.2 Tool wear at 10% coolant concentration Chipping Micro Chipping Normal wear Fig 4.3 Image of the failed tools, A chipping, B Micro chipping, C- normal wear At cutting conditions of low cutting speed/low feed, the tool life seems to be prolonged for both the low or high coolant concentration levels. The differences are only obvious at the initial period of tool wear. The tool wear rate for the initial period of cutting seems to show the differences, for low cutting speed, low feed and low coolant concentration, the tool wear) is 0.028mm/min (0.072mm/2.57min), nearly 366% higher than the low cutting speed, low feed and high coolant concentration, which is mm/min (0.020mm/2.57min). The tool wear rate, anyway converges at the later part of the cutting as though the coolant concentration has no effect on the wear rate, as shown in Fig

53 Fig 4.4 Tool wear for CC of 5% and 10% for low CS and low feed At the cutting condition of high cutting speed and high feed the above phenomena seems to be showing the opposite trend, the tool wear rate at the initial period does not show any differences between low and high coolant concentration but the tool wear rate seems to diverge at the later stage of cutting (Fig 4.5). Fig 4.5 Tool wear for CC of 5% and 10% for high CS and high feed 36

54 Fig 4.6 Tool life for CC of 5% and 10% at various cutting condition. The tool life comparison at various cutting conditions for both the coolant concentration of 5% and 10% are displayed in Fig 4.6 and Table 4.1. For the low cutting speed/low feed conditions, coolant concentration seems to have no effect or minimal effect on the tool life. For high cutting speed/high feed the tool life improved 33% at 10% coolant concentration. For high feed, low cutting speed there is 68% increase in tool life with coolant concentration of 10% whereas at the low feed, high cutting speed, the increase in tool life is 250% for cutting condition with coolant concentration of 10%. Table 4.1 Tool life for CC of 5% and 10% at various cutting condition Cutting Condition Feed 0.05mm/tooth Cutting speed 30m/min Feed 0.15mm/tooth Cutting speed 30m/min Feed 0.05mm/tooth Cutting speed 100m/min Feed 0.15mm/tooth Cutting speed 100m/min Tool life at CC of 5% (failure mode) 42.6 (V B ) 3.4 (CH) 0.8 (CH) 1.2 (V B ) Tool life at CC of 10% (failure mode) 41.2 (V B ) 5.7 (V B ) 2.8 (µch) 1.6 (V B ) Change -3% +68% +250% +33% 37

55 Fig 4.7 Tool wear for CC of 5% and 10% at various cutting condition. Fig 4.8 Tool wear for CC of 5% and 10% at various cutting condition Feed of 0.05mm/tooth versus 0.15mm/tooth on tool wear 38

56 Fig 4.9 Tool wear for feed of 0.05mm/tooth vs. 0.15mm/tooth (cc 5%, CS 30). At lower cutting speed and low coolant concentration the change in feed shows significant difference, low feed having high tool life and low tool wear (Fig 4.9). Fig 4.10 Tool wear for feed of 0.05mm/tooth vs. 0.15mm/tooth (cc 10%, CS 30). Comparing the same conditions at high coolant concentration/low cutting speed, the difference in feed shows similar results, low feed having high tool life and low tool wear (Fig 4.10) 39

57 Fig 4.11 Tool life for Feed of 0.05mm/tooth vs. 0.15mm/tooth (cc 5%, CS 100). For high cutting speed/low coolant concentration, tool life is low for both the high feed or low feed conditions, though the low feed caused the tool to fail first with chipping (Fig 4.11). The initial tool wear for low feed is low compared to the high feed condition, the following tool wear for both conditions seems to have the same rate as in Fig

58 Fig 4.12 Tool life for Feed of 0.05mm/tooth vs. 0.15mm/tooth (cc 10%, CS 100). Fig 4.13 Tool life for feed of 0.05mm/tooth and 0.15mm/tooth at various cutting condition. Table 4.2 Tool life for feed of 0.05mm/tooth and 0.15mm/tooth under various cutting condition 41

59 Cutting Condition Coolant concent. 5% Cutting speed 30m/min Coolant Concent. 10% Cutting speed 30m/min Coolant Concent. 5% Cutting speed 100m/min Coolant Concent. 10% Cutting speed 100m/min Feed 0.05mm/tooth (failure mode) 42.6 (V B ) 41.2 (V B ) 0.8 (CH) 2.8 (µch) Feed 0.15mm/tooth (failure mode) 3.4 (CH) 5.7 (V B ) 1.2 (V B ) 1.6 (V B ) Change -92% -86% +50% -43% An increase of 200% in feed from 0.05mm/tooth to 0.15mm/tooth reduces the tool life to about 90% for both low cutting speed/low coolant concentration and low cutting speed/high coolant concentration. Whereas at high cutting speed/low coolant concentration, the tool life improved 50% and the opposite happens with high coolant concentration/high cutting speed whereby tool life reduced about 43%. The overall result is shown in Table Cutting speed of 30m/min versus 100m/min on Tool wear 42

60 Fig 4.14 Tool life for CS 30m/mim and 100m/min (at CC5%, feed 0.05mm/tooth). Fig 4.15 Tool life for CS 30m/mim and 100m/min (at CC10%, feed 0.05mm/tooth). Figs 4.14 and 4.15 show similar trend as the feed above, at low coolant concentration/low feed low cutting speed, higher tool life and lower tool wear were 43

61 obtained as compared to high cutting speed at same condition. At high coolant concentration similar trend was observed. Fig 4.16 Tool life for CS 30m/mim and 100m/min (at CC 5%, Feed 0.15mm/tooth). At higher feed/low coolant concentration (Fig 4.16), or higher feed/higher coolant concentration (Fig 4.17), the tool wear was high hence tool life was very low. Though the tool life was better for higher coolant concentration conditions. 44

62 Fig 4.17 Tool life for CS 30m/mim and 100m/min (at CC10%, feed 0.15mm/tooth). Fig 4.18 Tool life for CS 30m/mim and 100m/min at various cutting condition. Table 4.3 Tool life at CS 30m/mim and 100m/min under various cutting condition 45

63 Cutting Condition Coolant Concent. 5% Feed 0.05mm/tooth Coolant Concent. 10% Feed 0.05mm/tooth Coolant Concent. 5% Feed 0.15mm/tooth Coolant Concent. 10% Feed 0.15mm/tooth Cut. speed 30m/min (failure Mode) 42.6 (V B ) 41.2 (V B ) 3.4 (CH) 5.7 (V B ) Cut. speed 100m/min (failure Mode) 0.8 (CH) 2.8 (µch) 1.2 (V B ) 1.6 (V B ) Change -98% -93% -65% -72% As shown in Table 4.3 an increase about 230% in cutting speed from 30m/mim to 100m/min reduced the tool life to about 100% for both low feed, low coolant concentration and low feed, high coolant concentration. Whereas at high feed, low coolant concentration and high feed, high coolant concentration conditions caused the tool life to reduce about 70%. M Rahman et. al. [9] reported in similar findings when end milling titanium alloy. They found that at high speed the coolant has less effect on the tool life. The coolant tends to be vaporized and forms a blanket that renders the coolant accessing to the toolchip interfaces. This explains why at high cutting speed conditions, the coolant has less impact on the tool life. The actual pictures of tool wear at each conditions are available in the Appendixes 4 through 18 46

64 4.1.4 DOE analysis on tool life (V B = 0.02mm) DOE analysis results on 3 factor 2 level, the cutting speed, feed and coolant concentration being the factors whereas the tool life as the response are discussed in this section. Factorial Fit: Tool life Act versus CS, Feed, CC Estimated Effects and Coefficients for Tool life Act (coded units) Term Effect Coef SE Coef T P Constant CS Feed CC CS*Feed CS*CC Feed*CC CS*Feed*CC Ct Pt S = 0.1 R-Sq = % R-Sq(adj) = % Fig 4.19 DOE for tool life results Using value of less 0.05 for significant level, all factors are significant in affecting the results of this experiment as shown in Fig

65 Fig 4.20 Pareto chart of the standardized effects The above pareto chart in Fig 4.20 and probability plot in Fig 4.21 confirm that all the three factors are significant and there are interactions between them which are also significant. 48

66 Fig 4.21 Normal probability plot of the standardized effects Fig 4.22 Main effects plot The main effects plot, Fig 4.22 shows the both the feed and cutting speed have greater influence on the Tool life compared with the with coolant concentration. 49

67 Analysis of Variance for Tool life Act (coded units) Source DF Seq SS Adj SS Adj MS F P Main Effects Way Interactions Way Interactions Curvature Residual Error Pure Error Total Fig 4.23 : 2 way and 3 way interactions The results with p value less than 0.05 shows there is 2 way interactions between all the 3 factors as well 3 way interactions (Fig 4.23). Fig 4.24 : 2 way and 3 way interactions graph The interaction plot in Fig 4.24, shows that the 2 way interactions between cutting speed and feed is very significant compared to the rest. 50

68 Estimated Coefficients for Tool life Act using data in uncoded units Term Coef Constant CS Feed CC CS*Feed CS*CC Feed*CC CS*Feed*CC Ct Pt Fig 4.25 : Estimated coefficients for tool life mathematical model Based on the above estimated coefficients in Fig 4.25, the mathematical model for the tool life, can be obtained as follows, Tool life = (CS) (feed ) (CC ) (CS*feed) (CS*CC) (feed*CC) ( CS*feed*CC ) Fig 4.26 : Response optimizer for Tool life 51

69 The response optimizer plot in Fig 4.26 shows the conditions to achieve maximum tool life. Increase in cutting speed and feed reduces the tool life tremendously. A similar study by K.A. Abou-El-Hossein et al. [10] on tool life of coated carbides in end milling of different mould steels showed similar results. In their study, carbide coated inserts were used in end milling of four different high speed steel tool, feed rate, axial and radial depths remained constant whereas the speed was varied to 4 levels for each material. The results show an increase in cutting speed generally causes a reduction in tool life. 52

70 4.2 Influence of machining conditions on surface roughness Coolant concentration of 5% versus 10% on surface roughness The coolant concentration seems to have little impact on the surface roughness at low cutting speed/low feed and high cutting speed/high feed. The actual experiment results for surface roughness is available in Appendix 2. The high feed, low cutting speed condition and lower coolant concentration seems to have better surface roughness, but the opposite is observed at low feed and high cutting speed conditions as shown in Fig 4.27 below. Fig 4.27 : Surface roughness at conditions coolant concentration 5% and 10% 53

71 4.2.2 Feed of 0.05mm/tooth versus 0.15mm/tooth on surface roughness There is a significant difference in the surface roughness for low feed and high feed conditions. The differences are more significant at high cutting speed conditions. Low feed provides low surface roughness at all conditions except at the low cutting speed, low coolant concentration condition, (Fig. 4.28). Fig 4.28 : Surface roughness at conditions feed 0.05mm/tooth and 0.15mm/tooth Shi Hyoung Ryu et al.,[11] in his roughness and texture generation on end milled surfaces study concluded that feedrate has a important role on surface profile generation. This study slightly differ, as they used feedrate and pick feed as the factors and remained the cutting speed as constant. Nevertheless low feedrate with large pick feed shows better surface roughness than that at high feedrate and small pick feed. Another influential factors considered in this study is also the tool run out and setting error which is important for final surface texture. 54

72 Dae Kyun Baek et al. [12, 13] reported that the surface roughness is sensitive to the feedrate and the run-out errors of the inserts when conducting a face milling investigation They mentioned when the feedrate is lowered, both the maximum surface roughness value and the arithmetic mean surface roughness value decreased Cutting speed of 30m/min versus 100m/min on Surface roughness The impact of cutting speed on surface roughness shows similar results as the feed. The differences are more significant at the high feed conditions as shown in Fig Fig 4.29 : Surface roughness at conditions cutting speed 30m/minand 100m/min Babur Ozcelik, et al. [14] included spindle speed, feedrate, depth of cut and step over as machining conditions when conducting a statistical modeling of surface roughness in high-speed milling. Interestingly this study was carried out under wet cutting conditions. Final mathematical model established indicated that spindle speed has 55

73 greater influence than feedrate on surface roughness. The feedrate had interactions with speed and depth of cut that are also significant. Similar interaction is also obvious in this study especially between cutting speed and feed as well as the feed and coolant concentration DOE analysis on surface roughness The DOE analysis on surface roughness (Fig 4.30) shows the significant factors affecting the surface roughness are the cutting speed and feed. Coolant concentration has very little impact. Factorial Fit: Surface roughness versus CS, Feed, CC Estimated Effects and Coefficients for Surface roughness (coded units) Term Effect Coef SE Coef T P Constant CS Feed CC CS*Feed CS*CC Feed*CC CS*Feed*CC Ct Pt S = R-Sq = 99.52% R-Sq(adj) = 98.22% Fig 4.30 : Significant factors affecting the Surface roughness 56

74 Fig 4.31 : Pareto chart of the standardized effects Fig 4.32 : Normal Probability Plot of the standardized effects 57

75 The Pareto Chart (Fig 4.31) and Normal probability plot (Fig 4.32) show the significant factors affecting the surface roughness are cutting speed, feed. There is 2 way interactions between cutting speed and feed and between feed and coolant concentration. The significant effect of feed and coolant concentration on surface roughness, makes the coolant concentration itself a significant factor. Fig 4.33 : Main Effects plot for Surface roughness Results show that the cutting speed and feed have greater impact on surface roughness than the coolant concentration. There is curve significant in this factors as the center points away from the corner point lines as shown in Fig

76 Analysis of Variance for Surface roughness (coded units) Source DF Seq SS Adj SS Adj MS F P Main Effects Way Interactions Way Interactions Curvature Residual Error Pure Error Total Fig 4.34 : 2 way and 3 way interactions between factors for surface roughness Fig 4.35 : Interactions plot between factors for surface roughness The analysis of variance (Fig 4.34) and the interactions plot (Fig 4.35) show there are greater interactions between cutting speed and feed but mild interactions between feed and coolant concentration. 59

77 Estimated Coefficients for Surface roughness using data in uncoded units Term Coef Constant CS Feed CC CS*Feed CS*CC Feed*CC CS*Feed*CC Ct Pt Fig 4.36 : Estimated coefficients for surface roughness formula Based on the above estimated coefficients, a mathematical model is established for surface roughness, Surface roughness = (CS) 57.73(feed ) 0.24 (CC ) (CS*feed) (CS*CC) (feed*CC) ( CS*feed*CC ) Fig 4.37 : Response optimizer for surface roughness The response optimizer plot (Fig 4.37) shows conditions to achieve minimum surface roughness. 60

78 4.3 Influence of machining conditions on cutting force Coolant concentration of 5% versus 10% on cutting force The actual Experiment data for the cutting forces are available in the Appendix 4. Coolant concentration has no or little impact on the cutting forces, at all conditions investigated (Fig 4.38). Fig 4.38 : Cutting force at conditions coolant concentration 5% and 10% 61

79 4.3.2 Feed of 0.05mm/tooth versus 0.15mm/tooth on cutting force Fig 4.39 : Cutting force at conditions feed 0.05mm/tooth and 0.15mm/tooth Feed has more significant impact on the cutting force as compared to cutting speed. Higher feed recorded higher cutting force as shown in Fig The 200% increase in feed from 0.05 to 0.15mm/tooth increased the cutting force around 150%. 62

80 4.3.3 Cutting speed of 30m/min versus 100m/min on Cutting Force Fig 4.40 Surface roughness at conditions cutting speed 30m/minand 100m/min Results in Fig 4.40 indicates that cutting speed has less impact on the cutting force. Similar results were also true for coolant concentrations. 63

81 4.3.4 DOE analysis on Cutting Force Factorial Fit: Cutting force versus CS, Feed, CC Estimated Effects and Coefficients for Cutting force (coded units) Term Effect Coef SE Coef T P Constant CS Feed CC CS*Feed CS*CC Feed*CC CS*Feed*CC Ct Pt S = R-Sq = 99.68% R-Sq(adj) = 98.82% Fig 4.41 Significant factors affecting the Cutting force Fig 4.42 Pareto chart of the standardized effects 64

82 Fig 4.43 Normal Probability Plot of the standardized effects The DOE results, in Fig 4.41 and the Pareto Chart in Fig 4.42 and the Normal probability plot in Fig 4.43 show the significant factors affecting the cutting force are cutting speed and feed. There is no 2 way or 3 way interaction between or among the 3 factors. The effect of feed was most significant, followed by cutting speed. 65

83 Fig 4.44 : Main Effects plot for cutting force The feed have greater impact of cutting force than the cutting speed and coolant concentration. As the center point results are not at the center of a straight line if drawn from each corner points (Fig 4.44), indicates that the curve is significant and these relationships is not linear relationship. Analysis of Variance for Cutting force (coded units) Source DF Seq SS Adj SS Adj MS F P Main Effects Way Interactions Way Interactions Curvature Residual Error Pure Error Total Fig 4.45 : Interactions between factors for cutting force 66

84 Fig 4.46 : Interactions plot between factors for cutting force The analysis of variance in Fig 4.45 and the interaction plots in Fig 4.46 show that there is no significant interactions between cutting speed and feed or coolant concentration. Estimated Coefficients for Cutting force using data in uncoded units Term Coef Constant CS Feed CC CS*Feed CS*CC Feed*CC CS*Feed*CC Ct Pt Fig 4.47 : Estimated coefficients for surface roughness formula 67

85 Based on the above estimated coefficients, the mathematical model for cutting force is as follows, Cutting force = (CS) (feed ) (CC ) (CS*feed) -0.04(CS*CC) 35.49(feed*CC) ( CS*feed*CC ) The above model could be further simplified based on the significant factors, Cutting force = (CS) (feed ) (CC ) Fig 4.48 : Response optimizer for Cutting Force The response optimizer plot in Fig 4.48 shows the conditions to achieve minimum cutting force 68

86 CHAPTER 5 CONCLUSION The results of experimental study carried out shows that for tool life, cutting speed, feed and coolant concentration are critical factors affecting the tool life. There are 2 way and 3 way interactions between these main effects which affecting the response. The relationship is a non-linear as the curvature is significant. The cutting speed and feed is more significant, impacting the tool life. The lower the cutting speed and the feed the higher the tool life is. Coolant concentration significantly affects the tool life improvement in certain milling condition especially at lower cutting speed and lower feed. At higher feed and cutting speed, the coolant concentration or the coolant itself does not have any impact on the tool life. For surface roughness the significant main effects are the feed and cutting speed. There are significant interactions between cutting speed and feed, feed and coolant concentration though coolant concentration does not directly affects the surface roughness, it reaction between feed does influence the results. The lower the speed and feed the lower is the surface roughness. The cutting force, which is directly influence the heat generated during cutting process which then impacts the tool life, cutting performance and product quality. The critical factor that affecting the cutting force is the feed. There are no significant interactions between any of the main effects. 69

87 Fig 4.49 : Response optimizer for all responses The optimum condition for this particular level of factors for all the expected three responses which are the maximum tool life, minimum surface roughness and minimum cutting force. To achieve this results the cutting speed has to be the lowest, the feed has to be lowest and coolant concentration has to be the highest. In actuality these conditions may not be the practical solution as the lower cutting speed and lower feed means longer cutting time, which translates to high cost. The higher coolant concentration also means higher cost and more effort to effluent treatment. A balance between these expected responses and the overall operational cost needs to be made. For example looking for allowable customer specification for surface roughness and achieve the minimum value will be a better choice rather than trying to achieve the lowest possible surface roughness. 70

88 REFERENCES 1. The 2007 World Machine-Tool Survey at a Glance, 2. N. R. Dhar, M. M.A Khan, A study on effects of Minimum Quantity Lubricant (MQL) on temperature, tool wear and product quality in turning AISI 9310 steel, N.R. Dhar, M Kamruzzaman, Effects of cryogenic cooling on temperature, tool wear, surface roughness and dimensional deviation in turning AISI 8740 steel by coated carbides, Jack A. Goldstone, Thoughts On The Industrial Revolution, HN9Goldstone.pdf 5. Metal cutting 4 th Edition, Edward M Trent, Paul K Wright, Butterworth Heinemann 6. David A. Stephenson, John S. Agapiou, Metal Cutting Theory and Practice, Marcel Dekker, Inc A tutorial on cutting fluids in machining, 8. E.O. Ezugwu1, J. Bonney1 and K.A. Olajire1, The Effect of Coolant Concentration on the Machinability of Nickel-Base, Nimonic C-263, Alloy 9. M Rahman, J Sun, Y.S. Wong, Z.G. Wang, K.S Neo, C.H, Effects of cooling supply strategies and cutting conditions on tool life in end milling titanium alloy. 2005, International Conference on leading Edge Manufacturing in 21 st Century K.A. Abou-El-Hossein, S Ramesh, M Hamdi, K Benyounis, Bashir M. Tool Life of coated carbides in end milling of different mould steels Shi Hyoung Ryu, Deok Ki Choi, Chong Nam Chu, 2006, Roughness and texture generation on end milled surfaces, International Journal of Machine Tools & Manufacture 46 (2006) Dae Kyun Baek, Tae Jo Ko, Hee Sool Kim, 2001, Optimization of feedrate in face milling operation using a surface roughness model, 71

89 International Journal of Machine Tools & Manufacture 41 (2001) Dae Kyun Baek, Tae Jo Ko, Hee Sool Kim, 1997, A dynamic surface roughness model for face milling, Precision Engineering, Babur Ozcelik, et al, The Statistical modeling of surface roughness in high-speed flat end milling, 2005, International Journal of Machine Tools & Manufacture 46 (2006)

90 APPENDICES Appendix 1 Experiment results for Tool Wear SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 10%, Feed 0.05, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 10%, Feed 0.05, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 10%, Feed 0.15, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 10%, Feed 0.15, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 7.5%, Feed 0.10, CS

91 SETTING STD CC % Feed Cut Machining Tool Wear N CS (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 7.5%, Feed 0.10, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 5%, Feed 0.05, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 5%, Feed 0.05, CS 100 SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 5%, Feed 0.15, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 5%, Feed 0.15, CS 30 SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 7.5%, Feed 0.10, CS

92 SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC 7.5%, Feed 0.10, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC DRY, 12 Dry Dry Feed 0.10, CS SETTING STD CC % Feed Cut Machining Tool Wear N rpm (mm/min) length time Flute 1 Flute 2 Flute 3 Flute 4 Avg 0 0 CC Dry, 1 Dry Dry Feed 0.05, CS

93 Appendix 2 Experiment results for Surface roughness SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 10%, Feed 0.05, CS SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 10%, Feed 0.05, CS SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 10%, Feed 0.15, CS SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 10%, Feed 0.15, CS 100 SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 7.5%, Feed 0.10, CS

94 SETTING STD CC % Feed (mm/min) N CS Cut length Machining time Surface roughness Avg CC 7.5%, Feed 0.10, CS SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 5%, Feed 0.05, CS SETTING STD CC % Feed (mm/min) N rpm Cut length Machining Surface roughness time Avg 0 0 CC 5%, Feed 0.05, CS 100 SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 5%, Feed 0.15, CS 100 SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 5%, Feed 0.15, CS 30 SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 7.5%, Feed 0.10, CS

95 SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC 7.5%, Feed 0.10, CS SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC DRY, 12 Dry Dry Feed 0.10, CS SETTING STD CC % Feed (mm/min) N rpm Cut length Machining time Surface roughness Avg CC Dry, 1 Dry Dry Feed 0.05, CS

96 Appendix 3 Experiment results for Cutting force SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 10%, Feed 0.05, CS SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 10%, Feed 0.05, CS SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 10%, Feed 0.15, CS SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 10%, Feed 0.15, CS SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 7.5%, Feed 0.10, CS

97 SETTING STD CC Feed % (mm/min) N CS Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 7.5%, Feed 0.10, CS SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 5%, Feed 0.05, CS SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 5%, Feed 0.05, CS 100 SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 5%, Feed 0.15, CS SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 5%, Feed 0.15, CS 30 SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 7.5%, Feed 0.10, CS

98 SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC 7.5%, Feed 0.10, CS SETTING STD CC % Feed (mm/min) N rpm Cut Machining length time Cutting Force Fy Fx Fz Ft 0 CC DRY, 12 Dry Dry Feed 0.10, CS SETTING STD CC Feed % (mm/min) N rpm Cut Machining Cutting Force length time Fy Fx Fz Ft 0 CC Dry, 1 Dry Dry Feed 0.05, CS

99 Appendix 4 Tool Before cut Tooth #1 Tooth #2 Tooth #3 Tooth #4 82

100 Appendix 5 Tool #1 CS 30, Feed 0.05, CC 5% Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #4 After Cut #5 After Cut #6 83

101 After Cut #6B 84

102 Appendix 6 Tool #2 CS 100, Feed 0.05, CC 5% Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 Tool 2 After Cut #1 Tool 2 Repeat 85

103 Appendix 7 Tool #3 CS 30, Feed 0. 15, CC 5% Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #2 86

104 Appendix 8 Tool #4 CS 100, Feed 0.15, CC 5% Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #2 After Cut #3 After Cut #3B 87

105 Appendix 9 Tool #5 CS 30, Feed 0.05, CC 10% Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #6 After Cut #7 88

106 Appendix 10 Tool #6 CS 100, Feed 0.05, CC 10% Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #4 89

107 Appendix 11 Tool #7 CS 30, Feed 0.15, CC 10% Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #4 90

108 Appendix 12 Tool #8 CS 100, Feed 0.15, CC 10% Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #3 91

109 Appendix 13 Tool #9 CS 65, Feed 0.10, CC 75 Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #5 92

110 Appendix `14 Tool #10 - CS 65, Feed 0.10, CC 75 Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #6 93

111 Appendix 15 Tool #11 - CS 65, Feed 0.10, CC 75 Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #3 After Cut #6 94

112 Appendix 16 Tool #12 - CS 65, Feed 0.10, CC 75 Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #3 After Cut #6 95

113 Appendix 17 Tool #13 CS 30, Feed 0.05, CC Dry Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #3 After Cut #6 96

114 Appendix 18 Tool #14 CS 30, Feed 0.05, CC Dry Tooth #1 Tooth #2 Tooth #3 Tooth #4 After Cut #1 After Cut #3 After Cut #6 97