SUMMER TRAINING PROJECT REPORT
India Yamaha Motor Pvt. Ltd.
SUBMITTED BY SAHIL MATHUR B.TECH MECHANICAL
SESSION: 2009-2013
Continental Institutes Of Engineering and Technology,Jalvehra(Punjab)
(Affiliated to Punjab Technical University, Jalandhar) PREFACE As a part of course curriculum of Bachelor of Technology we were asked to undergo 6 weeks summer training in any organisation so as to give us exposure to practical skill and competence to get us familiar with various activities taking place in the organisation.
I have put my sincere efforts to accomplish my objectives within the stipulated time. I have worked to my optimum potential to achieve desired goals. Being neophytes in the highly competitive world of technology, I came across some difficulties to make my objective a reality. With the kind help and genuine interest and the guidance of my supervisor. I tried my level best to conduct a research to gain a thorough knowledge about the project. I put the best of my efforts to bring out this piece of work. If anywhere something is found unacceptable or unnecessary to the theme; valuable suggestions are thankfully acknowledged.
Thanks and regards
Yours sincerely Sahil Mathur ACKNOWLEDGEMENT
I would like to express my gratitude to all the people who provided me with support and guidance throughout the course of my summer internship program.
Firstly I wish to thank Mr. Mahajan (Head-Plant Production), Mr. Subhash Chowdhry (Head-Machining dept.) for giving me an opportunity to undergo summer training at YAMAHA MOTOR INDIA Pvt. Ltd.,19/6 Mathura Road, Faridabad. I am also deeply indebted to Mr. Parvinder Gupta of Head Cylinder dept. without the supervision and continued guidance of whom it wouldn’t have been possible to complete this project.
I would also like to thank Mr. C.V. Sharma for providing me this wonderful opportunity to work with the YAMAHA family.
(SAHIL MATHUR) INDEX
1) Preface
2) Acknowledgement
3) Chapters:- Chapter 1 – Introduction
Chapter 2 - Manufacturing
Chapter 3 – Gear Hobbing
Chapter 4 – Cam Shaft
Chapter 5 – Heat Treatment
Chapter 6 – Electroplating
4) Bibleography CHAPTER 1 – INTRODUCTION
OVERVIEW - INDIAN AUTOMOBILE INDUSTRY
Over a period of more than two decades the Indian Automobile industry has been driving its own growth through phases. The entry of Suzuki Corporation in Indian passenger car manufacturing is often pointed as the first sign of India turning to a market economy. Since then the automobile sector witnessed rapid growth year after year. By late-90's the industry reached self reliance in engine and component manufacturing from the status of large scale importer.
With comparatively higher rate of economic growth rate index against that of great global powers, India has become a hub of domestic and exports business. The automobile sector has been contributing its share to the shining economic performance of India in the recent years. With the Indian middle class earning higher per capita income, more people are ready to own private vehicles including cars and two-wheelers. Product movements and manned services have boosted in the sales of medium and sized commercial vehicles for passenger and goods transport. Side by side with fresh vehicle sales growth, the automotive components sector has witnessed big growth. The domestic auto components consumption has crossed rupees 9000 crores and an export of one half size of this figure Overview Of Automobile Industry The Indian automobile industry is going through a technological change where each firm is engaged in changing its processes and technologies to sustain the competitive advantage and provide customers with the optimized products and services. Starting from the two wheelers, trucks, and tractors to the multi utility vehicles, commercial vehicles and the luxury vehicles, the Indian automobile industry has achieved tremendous amount of success in the recent years.
As per Society of Indian Automobile Manufacturers (SIAM) the market share of each segment of the industry is as follows:
The market shares of the segments of the automobile industry
Consistent growth and dedication have made the Indian automobile industry the second- largest tractor and two-wheeler manufacturer in the world. It is also the fifth-largest commercial vehicle manufacturer in the world. The Indian automobile market is among the largest in Asia.
The key players like Hindustan Motors, Maruti Udyog, Fiat India Private Ltd, Tata Motors, Bajaj Motors, Hero Motors, Ashok Leyland, Mahindra & Mahindra have been dominating the vehicle industry. A few of the foreign players like Toyota Kirloskar Motor Ltd., Skoda India Private Ltd., Honda Siel Cars India Ltd. have also entered the market and have catered to the customers’ needs to a large extent.
History of the Organization
Yamaha's history goes back over a hundred years to 1887 when Torakusu Yamaha founded the company, which began producing reed organs. The Yamaha Corporation in Japan (then Nippon Gakki Co., Ltd.) has grown to become the world's largest manufacturer of a full line of musical instruments, and a leading producer of audio/visual products, semiconductors and other computer related products, sporting goods, home appliances and furniture, specialty metals, machine tools, and industrial robots.
The Yamaha Motor Corporation, Ltd., begun on July 1, 1955, is a major part of the entire Yamaha group, but is a separately managed business entity from the Yamaha Corporation. The Yamaha Motor Corporation is the second largest manufacturer of motorcycles in the world. Yamaha Motor Corporation owns its wholly-owned subsidiary in the U.S. called Yamaha Motor Corporation, USA, that is handling not only motorcycles, but also snow mobiles, golf carts, outboard engines, and water vehicles, under the brand name of Yamaha as well.
In 1954 production of the first motorcycles began, a simple 125cc single- cylinder two-stroke. It was a copy of the German DKW design, which the British BSA Company had also copied in the post-war era and manufactured as the Bantam.
The first Yamaha, the YAI, known to Japanese enthusiasts as Akatombo, the "Red Dragonfly", established a reputation as a well-built and reliable machine. Racing successes helped boost its popularity and a second machine, the 175cc YCI was soon in production.
The first Yamaha-designed motorcycle was the twin-cylinder YDI produced in 1957. The racing version, producing 20bhp, won the Mount Asama race that year. Production was still modest at 15,811 motorcycles, far less than Honda or Suzuki.
By 1960 production had increased 600% to 138,000 motorcycles. In Japan a period of recession followed during which Yamaha, and the other major Japanese manufacturers, increased their exports so that they would not be so dependent on the home market.
To help boost export sales, Yamaha sent a team to the European Grand Prix in 1961, but it was not until the 1963 season that results were achieved.
After the Korean War the American economy was booming and Japanese exports were increasing. In 1962 Yamaha exported 12,000 motorcycles. The next year it was 36,000 and in 1964 production rose to 87,000. In 1963 Yamaha had produced a small batch of 250CC road racing motorcycles for sale, the air-cooled, twin-cylinder TDI. Ever since then Yamaha has built and sold motorcycles that could be raced successfully "straight out of the crate", and as a consequence Yamaha machines have won more road races than any other make, exposing Yamaha to a good deal of publicity.
The first overseas factory was opened in Siam in 1966 to supply Southeast Asia. In 1967 Yamaha production surpassed that of Suzuki by 4,000 at 406,000 units. Yamaha established a lead with the introduction of the first true trail bike "the 250cc single-cylinder DTI". The company also developed a two-liter, six-cylinder, double overhead-camshaft sports car unit for Toyota Motor. This proved helpful when Yamaha produced their own high- performance four-stroke motorcycles.In 1969 Yamaha built a full size road racing circuit near their main factory at Iwata.
By 1970 the number of models had expanded to 20 ranging from 50cc to 350cc, with production up to 574,000 machines, 60% of which were for export. That year Yamaha broke their two-stroke tradition by launching their first four-stroke motorcycle, the 650cc XSI vertical twin modeled on the famous Triumph twins.
In 1973 production topped one million (1,000,000) motorcycles per year for the first time, leaving Suzuki way behind at 642,000 and catching up on Honda's 1,836,000. During the 1970's Yamaha technicians concentrated on development of four-stroke models that were designed to pass the ever- increasing exhaust emission laws and to be more economical than the two- strokes that had made Yamaha's fortune. Over the years Yamaha produced some less successful motorcycles:
The TX750 twin of 1972.
The TX500 double overhead-camshaft, four-valve per cylinder, twin of 1973.
The XS750 shaft-drive, double overhead-camshaft, three cylinder of 1976.
And the XS Eleven, four-cylinder of 1977, was at the time the biggest bike produced by a Japanese manufacturer.
Other four-strokes were more successful, notably.
The XT500 single-cylinder trail bike of 1976.
And the XS350 single overhead-camshaft, twin.
Yamaha motor vehicles:
Two wheelers
Yamaha Vmax
Yamaha Tmax Utility vehicles
Yamaha-G16-Ultima
Yamaha Rhino700FI Auto4x4
Yamaha YFZ450R ATV
Yamaha Snowmobile
Watercraft
Yamaha Waverunner
COMPANY PROFILE
About India Yamaha Motor Pvt. Ltd.
Yamaha made its initial foray into India in 1985. Subsequently, it entered into a 50:50 joint-venture with the Escorts Group in
1996. However, in August 2001, Yamaha acquired its remaining stake becoming a 100% subsidiary of Yamaha Motor Co., Ltd,
Japan (YMC). In 2008, Mitsui & Co., Ltd. entered into an agreement with YMC to become a joint investor in the motorcycle manufacturing company "India Yamaha Motor Private
Limited (IYM)".
IYM operates from its state-of-the-art-manufacturing units at
Surajpur in Uttar Pradesh and Faridabad in Haryana and produces motorcycles both for domestic and export markets. With a strong workforce of more than 2,000 employees, IYM is highly customer-driven and has a countrywide network of over 400 dealers. Presently, its product portfolio includes VMAX
(1,679cc), MT01 (1,670cc), YZF-R1 (998cc), Fazer (153cc), FZ-
S (153cc), FZ16 (153cc), YZF-R15 (150cc), Gladiator Type SS &
RS (125cc), Gladiator Graffiti (125cc), G5 (106cc), Alba (106cc) and Crux (106cc).
Bikes produced in India Yamaha Motor Pvt. Ltd. :
Yamaha Vmax
Yamaha MT 01 Yamaha YZF R1
Yamaha R15
Yamaha Fazer
Yamaha FZ S
Yamaha FZ16 Yamaha YBR 100
Yamaha Alba
Yamaha Gladiator
Yamaha G5 Yamaha Crux CORE COMPETENCIES
We put customers first in everything we do. We take decisions keeping the customer in mind.
Challenging Spirit
We strive for excellence in everything we do and in the quality of goods & services we provide. We work hard to achieve what we commit & achieve results faster than our competitors and we never give up.
Team-work
We work cohesively with our colleagues as a multi-cultural team built on trust, respect, understanding & mutual co-operation. Everyone's contribution is equally important for our success.
What is Kando?
Kando is a Japanese word for the simultaneous feeling of deep satisfaction and intense excitement that people experience when they encounter something of exceptional value.
CORPORATE GOVERNANCE Basic Corporate Governance Policies Yamaha Motor Co., Ltd. (the “Company”) recognizes that corporate governance is an important tool to ensure disciplined management and maximize long-term corporate value. Based on this realization, the Company has been striving to speed up management decision-making; make the accountability system clearer; develop a transparent system of director selection and remuneration; and establish an internal control system. Because the Company considers corporate governance one of its most important management issues, measures to further strengthen corporate governance — such as improving supervisory functions — are being planned. At the same time, the Company will enhance Investor Relations services, in order to build on the relationship of trust with its shareholders and investors. Organizations and Systems for Management Decision-Making, Business Execution and Supervision
1) Directors and the Board of Directors
The Company has introduced an Executive Officer system to expedite business execution. It then strengthened management supervision by clarifying the respective roles of Executive Officers and the Board of Directors. Executive Officers are responsible for “business execution” itself, while the Board of Directors is charged with “approving the basic policies of the Yamaha Motor Group and supervising the Group’s business execution.” The Company’s Articles of Incorporation stipulate that the number of Directors shall not be more than fifteen (15). As of March 25, 2009, there were eleven (11) Directors, four (4) of whom are Outside Directors. The Board of Directors will in principle meet once every month, and whenever else it may be necessary. Directors and Executive Officers will serve one-year term, a period limited to assure accountability.
2) Executive Personnel Committee
In August 2001, the Company established the Executive Personnel Committee as an advisory body of the Board of Directors, in order to improve transparency in nominating candidates for Director and Executive Officer, and to determine the remuneration for these officers. The Committee is comprised of President and Chief Executive Officer, some other Directors of the Company, and some Outside Directors. It deliberates on candidates for Director and Executive Officer, the remuneration and bonus system and the overall direction of governance.
3) Internal Auditing
The Company established an Internal Control Auditing Division (consisting of twenty-four (24) staff members as of March 25, 2009), under the direct control of the President and Chief Executive Officer. The Division audit, based on annual audit plans, the appropriateness, reasonableness, and efficiency of business execution at the Company and each Group company, and submits evaluations and makes proposals
4) Yamaha Motor’s Corporate Governance System and Internal Control System (As of March 25, 2010) CHAPTER 2- MANUFACTURING
IYM's Manufacturing facilities comprises of 2 state-of-the-art Plants at - Faridabad (Haryana) and Surajpur (Uttar Pradesh). Currently 10 models roll out of the two Yamaha Plants. The infrastructure at both the plants supports production of motorcycles and it's parts for the domestic as well as oversees market. At the core are the 5-S and TPM activities that fuel our agile Manufacturing Processes. We have In- house facility for Machining, Welding processes as well as finishing processes of Electroplating and Painting till the assembly line. The stringent Quality Assurance norms ensure that our motorcycles meet the reputed International standards of excellence in every sphere. As an Environmentally sensitive organization we have the concept of "Environment-friendly technology" ingrained in our Corporate Philosophy. The Company boasts of effluent Treatment plant, Rain water - Harvesting mechanism, a motivated forestation drive. The IS0-14001 certification is on the anvil - early next year. All our endeavors give us reason to believe that sustainable development for Yamaha will not remain merely an idea in pipeline. We believe in taking care of not only Your Motoring Needs but also the needs of Future Generations to come.
RAW MATERIAL:-
The primary raw materials used in the manufacture of the body of motorcycle are metal, plastic and rubber. The motorcycle frame is composed almost completely of metal, as are the wheels. The frame may be overlaid with plastic. The tires are composed of rubber. The seat is made from a synthetic substance, such as polyurethane. The power system consists of a four-stroke engine, a carburetor to transform incoming fuel into vapor, a choke to control the air-fuel ratio, transmission, and drum brakes. The transmission system contains a clutch, consisting of steel ball flyweights and metal plates, a crankshaft, gears, pulleys, rubber belts or metal chains, and a sprocket. The
electrical system contains a battery, ignition wires and coils, diodes, spark plugs, head-lamps and taillights, turn signals and a horn.
A cylindrical piston, made of aluminum alloy (preferred because it is lightweight and conducts heat well), is an essential component of the engine. It is fitted with piston rings made of cast iron. The crankshaft and crankcase are made of aluminum. The engine also contains a cylinder barrel, typically made of cast iron or light alloy
THE MANUFACTURING PROCESS- 1. Raw materials as well as parts and components arrive at the manufacturing plant by truck or rail, typically on a daily basis. As part of the just-in-time delivery system on which many plants are scheduled, the materials and parts are delivered at the place where they are used or installed. 2. Manufacturing begins in the weld department with computer- controlled fabrication of the frame from high strength frame materials. Components are formed out of tubular metal and/or hollow metal shells fashioned from sheet metal. The various sections are welded together. This process involves manual, automatic, and robotic equipment. 3. In the plastics department, small plastic resin pellets are melted and injected into molds under high pressure to form various plastic body trim parts. This process is known as injection molding. 4. Plastic and metal parts and components are painted in booths in the paint department using a process known as powder-coating (this is the same process by which automobiles are painted). A powder-coating apparatus works like a large spray-painter, dispersing paint through a pressurized system evenly across the metal frame. 5. Painted parts are sent via overhead conveyors or tow motor (similar to a ski lift tow rope) to the assembly department where they are installed on the frame of the motorcycle. A motorcycle engine.
6. The engine is mounted in the painted frame, and various other components are fitted as the motorcycle is sent down the assembly line. 7. Wheels, brakes, wiring cables, foot pegs, exhaust pipes, seats, saddlebags, lights, radios, and hundreds of other parts are installed on the motorcycle frame. A Honda Gold Wing motorcycle, for example, needs almost as many parts to complete it as a Honda Civic automobile.
QUALITY CONTROL:- At the end of the assembly line, quality control inspectors undertake a visual inspection of the motorcycle's painted finish and fit of parts. The quality control inspectors also feel the motorcycles with gloved hands to detect any bumps or defects in the finish. Each motorcycle is tested on a dynamometer. Inspectors accelerate the motorcycle from 0-60 mph. During the acceleration, the "dyno" tests for acceleration and braking, shifting, wheel alignment, headlight and taillight alignment and function, horn function, and exhaust emissions. The finished product must meet international standards for performance and safety. After the dyno test, a final inspection is made of the completed motorcycle. The motorcycles are boxed in crates and shipped to customers across North America and around the world.
THE FUTURE
Motorcycles remain popular and the collecting and riding of antique models is just as popular as riding the new versions. While sleek, new versions will continue to be produces, A motorcycle transmission and disc brake system. it is anticipated that the value of older models will continue to rise. Manufacturing New Value
On the left is a conventional aluminum cylinder with a steel liner for the inner wall. On the right is the Yamaha "DiASil Cylinder" that needs no liner or cylinder wall plating. As a unit well suited to the mass- production of high-performance, low-cost cylinders, the DiASil Cylinder manufacturing technology was successful transferred to our manufacturing base in Indonesia.
TRANSFERRING TECHNOLOGY OVERSEAS:-
In 2004 Yamaha Motor successfully developed for the first time in the world a mass-production method for an all-aluminum (sleeveless, un- coated) cylinder named the "DiASil Cylinder" (*1). The production method for this DiASil Cylinder is in fact the fruit of Yamaha's advanced die-casting technology known as the "CF (controlled filling) Aluminum Die Casting Technology" that we have been developing for some years now. Conventional aluminum cylinders for motorcycles have either a cast steel sleeve or nickel plating on the inner wall of the cylinder to improve resistance to abrasion and prevent piston freeze-up. With Yamaha's DiASil Cylinder no liner or plating is needed (see photo). That makes this a mass-production aluminum cylinder with excellent cooling performance as well as nearly full recycle-ability at the end of its product life. This is another example of how Yamaha's philosophy of customer- oriented product creation is firmly implanted in our manufacturing technology as well. As a high-performance, low-cost cylinder that can be mass-produced, the DiASil Cylinder is a very effective manufacturing technology for the ASEAN region, one of the largest motorcycle markets in the world. When it came time for Yamaha to launch a new flagship model for the ASEAN market, the "T135," plans were initiated for it to use the DiASil Cylinder, and at the same time a project was launched to transfer its high-level manufacturing technology to the Yamaha manufacturing base in Indonesia. Staff from Japan and Indonesia worked together on this project and cleared one hurdle after another until the production of these cylinders was successfully started in Indonesia. Now many customers in the ASEAN region who rely on motorcycles in their daily lives are benefiting from the performance and cost efficiency of the world's first all-aluminum cylinder.
*1 DiASil: The name DiASil stands for Die casting Aluminum-Silicon alloy. An even distribution of hard silicon particles in this alloy greatly increases the abrasion resistance of the aluminum.
Thinner and larger parts for next- generation engineering and manufacturing Aluminum is light and highly rust (oxidation) resistant and easily manufactured, which is why it is used abundantly in motorcycle and outboard motor parts. However, with conventional die casting methods (*2) it was The YZF-R6's difficult to manufacture aluminum parts that aluminum main frame were both large and thin-walled, and this (left) and magnesium remained a technological problem in the rear frame (above) industry. When Yamaha succeeded in the development of its exclusive CF Aluminum Die Casting Technology this important hurdle was finally cleared and the way was opened to next-generation mass production methods for aluminum parts. With this CF Aluminum Die Casting Technology, the number of pieces needed to make components like motorcycle frames can be greatly reduced along with their overall weight. This also simplifies the manufacturing and assembly processes. In 2007, Yamaha also succeeded in the development of a CF Magnesium Die Casting Technology that made it possible for Yamaha to introduce the world's first magnesium rear frame on a production model for our YZF-R6.
*2 Die casting: In this casting method, molten metal is forced into a metal mold (die) at high pressure.
Theoretical value production, an ongoing quest Industrial engineering is an analytical method used in analyzing work efficiency. In the factory where Yamaha motorcycles are assembled, a further advancement of this method is used to calculate how much time is theoretically needed to perform each job, and this has led to an exclusive concept we call "theoretical value production." In this concept, the theoretical figure is in effect time that consists purely of "value work." "Theoretical figures" are applied to all work processes in our efforts to further improve productivity in our factories. Removing organizational boundaries - Yamaha's System Supplier (SyS) system In Yamaha's motorcycle operations we have adopted a System Supplier (SyS) system that combines the organizational functions of development, manufacturing and procurement into single SyS units for each part or component. By removing the boundaries between these organizational bodies, the parts production process can be made simultaneous in ways that improve quality and reduce lead times, while also improving cost consciousness. At the same time, this system is involved in instruction and training of specialists in our motorcycle manufacturing bases around the world. CHAPTER 3 -GEAR HOBBING
Hobbing is a machining process for making gears, splines, and sprockets on a hobbing machine, which is a special type of milling machine. The teeth or splines are progressively cut into the workpiece by a series of cuts made by a cutting tool called a hob. Compared to other gear forming processes it is relatively inexpensive but still quite accurate, thus it is used for a broad range of parts and quantities. It is the most widely used gear cutting process for creating spur and helical gears] and more gears are cut by hobbing than any other process since it is relatively quick and inexpensive.
Process Hobbing uses a hobbing machine with two non-parallel spindles, one mounted with a blank workpiece and the other with the hob. The angle between the hob's spindle and the workpiece's spindle varies, depending on the type of product being produced. For example, if a spur gear is being produced, then the hob is angled equal to the helix angle of the hob; if a helical gear is being produced then the angle must be increased by the same amount as the helix angle of the helical gear. The two shafts are rotated at a proportional ratio, which determines the number of teeth on the blank; for example, if the gear ratio is 40:1 the hob rotates 40 times to each turn of the blank, which produces 40 teeth in the blank. Note that the previous example only holds true for a single threaded hob; if the hob has multiple threads then the speed ratio must be multiplied by the number of threads on the hob. The hob is then fed up into workpiece until the correct tooth depth is obtained. Finally the hob is fed into the workpiece parallel to the blank's axis of rotation. Up to five teeth can be cut into the workpiece at the same time. Oftentimes multiple gears are cut at the same time. For larger gears the blank is usually gashed to the rough shape to make hobbing easier. Modern hobbing machines, also known as hobbers, are fully automated machines that come in many sizes, because they need to be able to produce anything from tiny instrument gears up to 10 ft (3.0 m) diameter marine gears. Each gear hobbing machine typically consists of a chuck and tailstock, to hold the workpiece or a spindle, a spindle on which the hob is mounted, and a drive motor. For a tooth profile which is a theoretical involute, the fundamental rack is straight-sided, with sides inclined at the pressure angle of the tooth form, with flat top and bottom. The necessary addendum correction to allow the use of small-numbered pinions can either be obtained by suitable modification of this rack to a cycloidal form at the tips, or by hobbing at other than the theoretical pitch circle diameter. Since the gear ratio between hob and blank is fixed, the resulting gear will have the correct pitch on the pitch circle, but the tooth thickness will not be equal to the space width. Hobbing machines are characterised by the largest module or pitch diameter it can generate. For example, a 10 in (250 mm) capacity machine can generate gears with a 10 in pitch diameter and usually a maximum of a 10 in face width. Most hobbing machines are vertical hobbers, which means the blank is mounted vertically. Horizontal hobbing machines are usually used for cutting longer workpieces; i.e. cutting splines on the end of a shaft. Hob
A gear hob in a hobbing machine with a finished gear. The hob is the cutter used to cut the teeth into the workpiece. It is cylindrical in shape with helical cutting teeth. These teeth have grooves that run the length of the hob, which aid in cutting and chip removal. There are also special hobs designed for special gears such as the spline and sprocket gears. The cross-sectional shape of the hob teeth are almost the same shape as teeth of a rack gear that would be used with the finished product. There are slight changes to the shape for generating purposes, such as extending the hob's tooth length to create a clearance in the gear's roots. Each hob tooth is relieved on the back side to reduce friction. Most hobs are single-thread hobs, but double-, and triple-thread hobs increase production rates. The downside is that they are not as accurate as single-thread hobs. This list outlines types of hobs:
. Roller chain sprocket hobs . Worm wheel hobs . Spline hobs . Chamfer hobs . Spur and helical gear hobs . Straight side spline hobs . Involute spline hobs . Serration hobs . Semitopping gear hobs Uses
Hobbing is used to make following types of finished goods:
. Cycloid gears (see below) . Helical gears . Involute gears . Ratchets . Splines . Sprockets . Spur gears . Worm gears
Hobbing is used to produce most throated worm wheels, but certain tooth profiles cannot be hobbed. If any portion of the hob profile is perpendicular to the axis then it will have no cutting clearance generated by the usual backing off process, and it will not cut well.
Cycloidal forms For cycloidal gears (as used in BS978-2 Specification for fine pitch gears) and cycloidal-type gears each module, ratio and number of teeth in the pinion requires a different hobbing cutter so the technique is only suitable for large volume production. To circumvent this problem a special war-time emergency circular arc gear standard was produced giving a series of close to cycloidal forms which could be cut with a single hob for each module for eight teeth and upwards to economize on cutter manufacturing resources. A variant on this is still included in BS978-2a (Gears for instruments and clockwork mechanisms. Cycloidal type gears. Double circular arc type gears). Tolerances of concentricity of the hob limit the lower modules which can be cut practically by hobbing to about 0.5 module. Gear cutting is the process of creating a gear. The most common processes include hobbing, broaching, and machining; other processes include shaping, forging, extruding, casting, and powder metallurgy. Gears are commonly made from metal, plastic, and wood.
PROCESS:-
Broaching For very large gears or splines, a vertical broach is used. It consists of a vertical rail that carries a single tooth cutter formed to create the tooth shape. A rotary table and a Y axis are the customary axes available. Some machines will cut to a depth on the Y axis and index the rotary table automatically. The largest gears are produced on these machines. Other operations such as broaching work particularly well for cutting teeth on the inside. The downside to this is that it is expensive and different broaches are required to make different sized gears. Therefore it is mostly used in very high production runs.
Hobbing Hobbing is a method by which a hob is used to cut teeth into a blank. The cutter and gear blank are rotated at the same time to transfer the profile of the hob onto the gear blank. The hob must make one revolution to create each tooth of the gear. Used very often for all sizes of production runs, but works best for medium to high.
Machining Spur may be cut or ground on a milling machine or jig grinder utilizing a numbered gear cutter, and any indexing head or rotary table. The number of the gear cutter is determined by the tooth count of the gear to be cut. To machine a helical gear on a manual machine, a true indexing fixture must be used. Indexing fixtures can disengage the drive worm, and be attached via an external gear train to the machine table's handle (like a power feed). It then operates similarly to a carriage on a lathe. As the table moves on the X axis, the fixture will rotate in a fixed ratio with the table. The indexing fixture itself receives its name from the original purpose of the tool: moving the table in precise, fixed increments. If the indexing worm is not disengaged from the table, one can move the table in a highly controlled fashion via the indexing plate to produce linear movement of great precision (such as a vernier scale). There are a few different types of cutters used when creating gears. One is a rack shaper. These are straight and move in a direction tangent to the gear, while the gear is fixed. They have six to twelve teeth and eventually have to be moved back to the starting point to begin another cut. A popular way to build gears is by form cutting. This is done by taking a blank gear and rotating a cutter, with the desired tooth pattern, around its periphery. This ensures that the gear will fit when the operation is finished.
Shaping The old method of gear cutting is mounting a gear blank in a shaper and using a tool shaped in the profile of the tooth to be cut. This method also works for cutting internal splines. Another is a pinion-shaped cutter that is used in a gear shaper machine. It is basically when a cutter that looks similar to a gear cuts a gear blank. The cutter and the blank must have a rotating axis parallel to each other. This process works well for low and high production runs. CHAPTER 4-CAMSHAFT
Material Camshafts can be made out of several different types of material. These include: Chilled iron castings: this is a good choice for high volume production. A chilled iron camshaft has a resistance against wear because the camshaft lobes have been chilled, generally making them harder. When making chilled iron castings, other elements are added to the iron before casting to make the material more suitable for its application. Billet Steel: When a high quality camshaft is required, engine builders and camshaft manufacturers choose to make the camshaft from steel billet. This method is also used for low volume production. This is a much more time consuming process, and is generally more expensive than other methods. However the finished product is far superior. When making the camshaft, CNC lathes, CNC milling machines and CNC camshaft grinders will be used. Different types of steel bar can be used, one example being EN40b. When manufacturing a camshaft from EN40b, the camshaft will also be heat treated via gas nitriding, which changes the micro-structure of the material. It gives a surface hardness of 55-60 HRC. These types of camshafts can be used in high-performance engines. Timing:-
The relationship between the rotation of the camshaft and the rotation of the crankshaft is of critical importance. Since the valves control the flow of air/fuel mixture intake and exhaust gases, they must be opened and closed at the appropriate time during the stroke of the piston. For this reason, the camshaft is connected to the crankshaft either directly, via a gear mechanism, or indirectly via a belt or chain called a timing belt or timing chain. Direct drive using gears is unusual because the frequently-reversing torque caused by the slope of the cams tends to quickly wear out gear teeth. Where gears are used, they tend to be made from resilient fibre rather than metal. In some designs the camshaft also drives the distributor and the oil and fuel pumps. Some General Motors vehicles also have the power steering pump driven by the camshaft. Also on early fuel injection systems, cams on the camshaft would operate the fuel injectors. An alternative used in the early days of OHC engines was to drive the camshaft(s) via a vertical shaft with bevel gears at each end. This system was, for example, used on the pre-WW1 Peugeot and Mercedes Grand Prix cars. Another option was to use a triple eccentric with connecting rods; these were used on certain W.O. Bentley-designed engines and also on the Leyland Eight. In a two-stroke engine that uses a camshaft, each valve is opened once for each rotation of the crankshaft; in these engines, the camshaft rotates at the same rate as the crankshaft. In a four-stroke engine, the valves are opened only half as often; thus, two full rotations of the crankshaft occur for each rotation of the camshaft. The timing of the camshaft can be advanced to produce better low end torque or it can be reduced to produce better high end torque. Duration Duration is the number of crankshaft degrees of engine rotation during which the valve is off the seat. As a generality, greater duration results in more horsepower. The RPM at which peak horsepower occurs is typically increased as duration increases at the expense of lower rpm efficiency (torque). Duration can often be confusing because manufacturers may select any lift point to advertise a camshaft's duration and sometimes will manipulate these numbers. The power and idle characteristics of a camshaft rated at .006" will be much different than one rated the same at .002". Many performance engine builders gauge a race profile's aggressiveness by looking at the duration at .020", .050" and .200". The .020" number determines how responsive the motor will be and how much low end torque the motor will make. The .050" number is used to estimate where peak power will occur, and the .200" number gives an estimate of the power potential. A secondary effect of increase duration is increasing overlap, which is the number of crankshaft degrees during which both intake and exhaust valves are off their seats. It is overlap which most affects idle quality, inasmuch as the "blow-through" of the intake charge which occurs during overlap reduces engine efficiency, and is greatest during low RPM operation. In reality, increasing a camshaft's duration typically increases the overlap event, unless one spreads lobe centers between intake and exhaust valve lobe profiles. Lift The camshaft "lift" is the resultant net rise of the valve from its seat. The further the valve rises from its seat the more airflow can be realised, which is generally more beneficial. Greater lift has some limitations. Firstly, the lift is limited by the increased proximity of the valve head to the piston crown and secondly greater effort is required to move the valve's springs to higher state of compression. Increased lift can also be limited by lobe clearance in the cylinder head construction, so higher lobes may not necessarily clear the framework of the cylinder head casing. Higher valve lift can have the same effect as increased duration where valve overlap is less desirable. Higher lift allows accurate timing of airflow; although even by allowing a larger volume of air to pass in the relatively larger opening, the brevity of the typical duration with a higher lift cam results in less airflow than with a cam with lower lift but more duration, all else being equal. On forced induction motors this higher lift could yield better results than longer duration, particularly on the intake side. Notably though, higher lift has more potential problems than increased duration, in particular as valve train rpm rises which can result in more inefficient running or loss or torque. Cams that have too high a resultant valve lift, and at high rpm, can result in what is called "valve bounce", where the valve spring tension is insufficient to keep the valve following the cam at its apex. This could also be as a result of a very steep rise of the lobe and short duration, where the valve is effectively shot off the end of the cam rather than have the valve follow the cams’ profile. This is typically what happens on a motor over rev. This is an occasion where the engine rpm exceeds the engine maximum design speed. The valve train is typically the limiting factor in determining the maximum rpm the engine can maintain either for a prolonged period or temporarily. Sometimes an over rev can cause engine failure where the valve stems become bent as a result of colliding with the piston crowns. Position Depending on the location of the camshaft, the cams operate the valves either directly or through a linkage of pushrods and rockers. Direct operation involves a simpler mechanism and leads to fewer failures, but requires the camshaft to be positioned at the top of the cylinders. In the past when engines were not as reliable as today this was seen as too much bother, but in modern gasoline engines the overhead cam system, where the camshaft is on top of the cylinder head, is quite common. Number of camshafts Main articles: overhead valve and overhead cam While today some cheaper engines rely on a single camshaft per cylinder bank, which is known as a single overhead camshaft (SOHC), most[quantify] modern engine designs (the overhead-valve or OHV engine being largely obsolete on passenger vehicles), are driven by a two camshafts per cylinder bank arrangement (one camshaft for the intake valves and another for the exhaust valves); such camshaft arrangement is known as a double or dual overhead cam (DOHC), thus, a V engine, which has two separate cylinder banks, may have four camshafts (colloquially known as a quad-cam engine. More unusual is the modern W engine (also known as a 'VV' engine to distinguish itself from the pre-war W engines) that has four cylinder banks arranged in a "W" pattern with two pairs narrowly arranged with a 15 degree separation. Even when there are four cylinder banks (that would normally require a total of eight individual camshafts), the narrow-angle design allows the use of just four camshafts in total. For theBugatti Veyron, which has a 16 cylinder W engine configuration, all the four camshafts are driving a total of 64 valves. The overhead camshaft design adds more valvetrain components that ultimately incur in more complexity and higher manufacturing costs, but this is easily offset by many advantages over the older OHV design: multi-valve design, higher RPM limit and design freedom to better place valves, ignition (Spark-ignition engine) and intake/exhaust ports. Maintenance The rockers or cam followers sometimes incorporate a mechanism to adjust and set the valve play through manual adjustment, but most modern auto engines have hydraulic lifters, eliminating the need to adjust the valve lash at regular intervals as the valvetrain wears, and in particular the valves and valve seats in the combustion chamber. Sliding friction between the surface of the cam and the cam follower which rides upon it is considerable. In order to reduce wear at this point, the cam and follower are both surface hardened, and modern lubricant motor oils contain additives specifically to reduce sliding friction. The lobes of the camshaft are usually slightly tapered, causing the cam followers or valve lifters to rotate slightly with each depression, and helping to distribute wear on the parts. The surfaces of the cam and follower are designed to "wear in" together, and therefore when either is replaced, the other should be as well to prevent excessive rapid wear. In some engines, the flat contact surfaces are replaced with rollers, which eliminate the sliding friction and wear but adds mass to the valvetrain.
Camshaft design:-
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Don't just depend on catalogs read full caption
For some of us, camshafts are a lot like marriage-we understand the concept but cannot fathom exactly how to make it work. For example, why is duration always measured in crankshaft degrees? And why do you not begin measuring duration until 0.050 inch of lift? Or why do camshaft manufacturers grind a cam advanced? What does the lobe separation angle have to do with performance? And why does advancing the camshaft seem to help low-end torque?
The science behind camshaft design is as advanced as anything in a race car, so most of us-including experienced engine builders-depend on the manufacturer to help spec the right cam for a particular engine package. Still, there is a science that controls every part of the design of your camshaft, and understanding why different parts of the cam are designed a particular way can help you determine what works best for your needs.
Of all the different parts of the cam, most are relatively straightforward (e.g., the journals and distributor gear). The cam lobes, one for each valve, contain all the variables. The cam lobes control not only total lift and when the valves open and close, but also valve speed, acceleration, overlap, and even how much cylinder pressure is developed at speed. There are a few parts of the lobe design critical to achieving this.
A cam chart like this can read full caption
Base Circle is the term for the backside of the lobe. When the lifter is on the base circle of the lobe, the valve should be closed. It is also commonly called the heel of the lobe. The size of the base circle is important in relationship to the cam's lift. A smaller base circle allows more lobe lift, but it can also allow the camshaft to flex and throw off the timing events.
Ramps are the parts of the lobe where the lifter is either moved up or allowed to drop. Every lobe has two ramps-an opening ramp and a closing ramp. In performance camshafts, the curve of the ramps changes several times, which is a tool the cam designer uses to fine-tune the speed and acceleration of the lifter.
An asymmetrical lobe refers to opening and closing ramps that are not identical. In order to maximize both valve speed and control, the lifter must be raised in a different manner from which it is lowered. For example, in performance applications the valve is generally opened as quickly as possible, but the speed of the valve slows significantly as it nears maximum lift to keep it from lofting. But on the closing side, the valve must be seated relatively gently to keep it from bouncing. An asymmetrical lobe design allows this.
The nose of the lobe marks the area where the valve is fully opened. The highest point of lift is the lobe's centerline. The intake centerline is measured as crankshaft degrees after top dead center (TDC). The exhaust centerline is expressed as the number of degrees of the crankshaft's position before TDC. Incidentally, a cam's position is always measured relative to the crankshaft's position because that tells you where the piston is and which stroke it is on (intake, compression, power, or exhaust).
Lobe lift is the amount the cam lobe raises the lifter. It isn't the same as valve lift because the rocker arm is a lever that multiplies the amount of lobe lift to get the final valve lift. The lobe lift is equal to the diameter of the lobe at the centerline minus the diameter of the base circle.
Many cams are ground with read full caption
Obviously, the primary job of the camshaft is to control the timing of the intake and exhaust valve events. This is done with separate intake and exhaust lobes. The relationship of these lobes to each other is called lobe separation. Lobe separation is measured in degrees between the peak of the exhaust lobe (maximum valve lift) and the peak of the intake lobe. Essentially, it is half the angle in crankshaft degrees of rotation between peak exhaust valve lift and peak intake valve lift. If the duration remains the same, increasing the lobe separation angle decreases overlap, while decreasing it does the opposite.
"Typically, if all other factors are kept constant, widening the lobe separation produces a wider, flatter torque curve that holds better at higher rpm but can sometimes cause a lazy throttle response," explains Billy Godbold, a camshaft designer at Comp Cams. "Tightening the separation generally produces the opposite effect-more mid-range torque and a faster revving engine, but with a tighter power range."
There are other reasons to change lobe separation to influence engine performance. For example, if you are running a long rod package and keep the stroke the same, you will dwell the piston near TDC longer. To maintain similar overlap characteristics, you may need to open up the lobe separation and shorten the duration.
Overlap is the point in crank rotation when both the intake and exhaust valves are open simultaneously. This happens at the end of the exhaust stroke when the exhaust valve is closing and the intake is opening. During the period of overlap, the intake and exhaust ports can communicate with each other. Ideally, you want the scavenge effect from the exhaust port to pull the air/fuel mixture from the intake port into the combustion chamber to achieve more efficient cylinder filling. A poorly designed cam and port combination, however, can cause reversion, where exhaust gases push their way past the intake valve and into the intake tract. Several factors influence how much overlap is ideal for your engine. Small combustion chambers typically require minimal overlap, as do engines designed to maximize low-rpm torque. Most current stock car racing engines depend on high rpm to take advantage of better gear ratios, so more overlap is normally helpful. When the revolutions per minute increase, the intake valve is open for a shorter period of time. The same amount of air and fuel must be pulled into the combustion chamber in less time, and the engine can use all the help it can get to fill the chamber. Increasing the overlap can help here.
Long rod/stroke packages, which are becoming increasingly popular in circle track racing, also have an effect here just as with the lobe separation. Because the piston dwells near TDC longer, it makes the combustion chamber appear smaller to the incoming air/fuel charge. Because of this, less overlap is needed to properly fill the chamber. Along with reduced vacuum and potential reversion problems, running too much overlap in your race engine sends unburned fuel out of the exhaust pipes, reducing fuel efficiency. For most short track racers, this isn't a problem. But if you run into a fuel-mileage situation to cut out pit stops, it can be helpful.
When degreeing your cam, always... read full caption
Duration is the amount of time, measured in degrees of crankshaft rotation, that the valve-either intake or exhaust-is open. Most camshaft manufacturers list both an advertised duration and duration at 0.050 inch. We'll discuss this in more detail later. As engine rpm increases, the engine eventually reaches a point at which it has trouble effectively filling the cylinders with the air/fuel charge in the short amount of time the intake valve is open. The same thing holds true with the spent exhaust gases. The simple answer here is to increase the amount of time the valve is open, which is referred to as increasing its duration. For example, to maximize flow during the exhaust stroke, many extreme performance cam designs begin opening the exhaust valve near the midpoint of the power stroke. This may seem harmful to power production, but the idea is to have the exhaust valve fully open when the exhaust stroke begins. During the power stroke, the burning fuel has used about 80 percent of its available force on the piston by the time the crank has turned 90 degrees. The bottom half of the power stroke actually provides very little in terms of engine power, and it can be better used to help exhaust the combustion chamber so that there is more efficient cylinder filling on the intake stroke.
Here's a statement that you already know: The valve is most efficient at allowing air (either intake or exhaust) to flow past it when it is fully open. Not to insult your intelligence, but we needed to get that out of the way. What that statement tells us is that in terms of achieving maximum engine performance, the amount of time the camshaft is either raising or lowering the valve is effectively wasted. In a perfect world, the valve would be completely seated to seal the chamber, then it would fully open instantly at the appropriate time to allow maximum flow.
To get as close to this as possible, maximum race cams use extreme lobe profiles that open and close the valve ridiculously quickly. This requires stronger valvesprings and lightweight valvetrain components to maintain valve control, and engine builders and cam designers alike are still researching ways to open the valves even faster.
A more aggressive cam with high lift velocities allows you to shorten the duration in certain situations, which can help power. "Aggressive ramps allow the valve to reach maximum velocity sooner, allowing more area for a given duration," says Godbold. "Engines with significant airflow or compression restrictions [often seen in Street Stock classes or other classes with small carburetors] seem to love aggressive profiles. This is likely due to the increased signal to get more of the charge through the restriction. The decreased seat timing also results in earlier intake closing and more cylinder pressure." If you are required to race read full caption
Currently, one of the greatest limiting factors when it comes to aggressive camshaft profiles is the requirement many tracks and sanctioning bodies have mandating flat-tappet lifters. A flat tappet limits how quickly you can raise the lifter because the lobe angle can only be raised a specific amount before the edge of the lifter begins digging into the side of the lobe. Increasing the diameter of the lifter allows the lifter to slide over the face of the lobe again, so if your rules allow, try running a larger lifter combination. Godbold provided us with a few interesting numbers concerning maximum velocities for lifters. For example, with a stock Chevy 0.842 diameter lifter, the maximum velocity is 0.00700 inch per degree. If you use a Ford 0.875 lifter, that increases the maximum lift to 0.00735 inch per degree of rotation. That may not sound like much to you and me, but it's enough to make a cam designer drool. Of course, those numbers pale in comparison to a roller lifter, which doesn't have the same limits and is definitely the way to go in a racing application if the rules allow it. The maximum velocity for a performance roller lifter is typically around 0.009 per degree. Now we are talking about a really big difference.
One thing that confuses many new racers is that cam companies typically list both an advertised duration and a duration measured when the lifter is 0.050 inch off of the seat. The problem is that different manufacturers use different points to determine duration. There are different reasons for this, but few of them concern anyone other than the cam designers and their respective marketing departments. That's why lift at 0.050 has become an industry standard.
Usually, a valve doesn't begin flowing a significant amount of air until it has been raised several thousandths off of the seat. Also, differences in lash make it difficult to determine the exact moment a valve leaves the seat. Finally, duration at 0.050 inch of lobe lift is easier to measure and makes life easier for anyone setting the cam timing with a degree wheel. " . . . it's easier to measure the 0.050 duration than the advertised duration because the tappet velocity is much higher after it has had some time to accelerate," Godbold explains. "When using a cam degree wheel and a dial indicator, there is far less uncertainty about where the degree wheel is oriented when the dial indicator reads exactly 0.050 inch of lift than with lifts in the 0.004 to 0.020 range."
By using special timing sets, you can change the angle of the cam relative to the crankshaft. Spinning the cam forward so that the valve opening events happen sooner is called advancing the cam. Retarding the cam is just the opposite. Most camshaft manufacturers grind in around 4 degrees of advance into their cams so that it is automatic when you install your cam with the zero marks on the timing set. This is very common with street cams but varies with different race cams. Make sure you know what you have.
"Typically, engines respond better with a few degrees advance," Godbold explains. "This is likely due to the importance of the intake closing point on performance. Earlier intake closing leads to increased cylinder pressure and better responsiveness." As a general rule of thumb, advancing the cam will help low-end torque, but if your engine is dying by the flag stand, retarding the cam a few degrees should help extend high-rpm power a bit.
The information we've provided is a lot to digest, but don't worry. Most cam manufacturers have helpful tech departments to work you through the rough spots. To make things just a little easier, here's a cheat sheet for cam changes and the typical result. Remember, all engine packages are different, and your results may vary. These are only general guidelines.
CHAPTER 5- HEAT TEATMENT
Heat treating is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such asglass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering andquenching. It is noteworthy that while the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.
Heat treating furnace at 1,800 °F(980 °C) Metallic materials consist of a microstructure of small crystals called "grains" or crystallites. The nature of the grains (i.e. grain size and composition) is one of the most effective factors that can determine the overall mechanical behavior of the metal. Heat treatment provides an efficient way to manipulate the properties of the metal by controlling the rate of diffusion and the rate of cooling within the microstructure. There are two mechanisms that may change an alloy's properties during heat treatment. Themartensite transformation causes the crystals to deform intrinsically. The diffusion mechanism causes changes in the homogeneity of the alloy. The crystal structure consists of atoms that are grouped in a very specific arrangement, called a lattice. In most elements, this order will rearrange itself, depending on conditions like temperature and pressure. This rearrangement, called allotropy or polymorphism, may occur several times, at many different temperatures for a particular metal. In alloys, this rearrangement may cause an element that will not normally dissolve into the base metal to suddenly become soluble, while a reversal of the allotropy will make the elements either partially or completely insoluble. When in the soluble state, the process of diffusion causes the atoms of the dissolved element to spread out, attempting to form a homogenous distribution within the crystals of the base metal. If the alloy is cooled to an insoluble state, the atoms of the dissolved constituents (solutes) may migrate out of the solution. This type of diffusion, called precipitation, leads to nucleation, where the migrating atoms group together at the grain- boundaries. This forms a microstructure generally consisting of two or more distinct phases. Steel that has been cooled slowly, for instance, forms a laminated structure composed of alternating layers of ferrite and cementite, becoming softpearlite. Unlike iron-based alloys, most heat treatable alloys do not experience a ferrite transformation. In these alloys, the nucleation at the grain-boundaries often reinforces the structure of the crystal matrix. These metals harden by preciptation. Typically a slow process, depending on temperature, this is often referred to as "age hardening. Many metals and non-metals exhibit a martensite transformation when cooled quickly. When a metal is cooled very quickly, the insoluble atoms may not be able to migrate out of the solution in time. This is called a "diffusionless transformation." When the crystal matrix changes to its low temperature arrangement, the atoms of the solute become trapped within the lattice. The trapped atoms prevent the crystal matrix from completely changing into its low temperature allotrope, creating shearing stresses within the lattice. When some alloys are cooled quickly, such as steel, the martensite transformation hardens the metal, while in others, like aluminum, the alloy becomes softer.
Effect Of Composition:- Phase diagram of an iron-carbon alloying system. Phase changes occur at different temperatures (vertical axis) for different compositions (horizontal axis). The dotted lines mark the eutectoid and eutectic compositions. The specific composition of an alloy system will usually have a great effect on the results of heat treating. If the percentage of each constituent is just right, the alloy will form a single, continuous microstructure upon cooling. Such a mixture is said to be eutectoid. However, If the percentage of the solutes varies from the eutectoid mixture, two or more different microstructures will usually form simultaneously. A hypoeutectoid solution contains less of the solute than the eutectoid mix, while a hypereutectoid solution contains more.
Eutectoid alloys A eutectoid alloy is similar in behavior to a eutectic alloy. A eutectic alloy is characterized by having a single melting point. This melting point is lower than that of any of the constituents, and no change in the mixture will lower the melting point any further. When a molten eutectic alloy is cooled, all of the constituents will crystallize into their respective phases at the same temperature. A eutectoid alloy is similar, but the phase change occurs, not from a liquid, but from a solid solution. Upon cooling a eutectoid alloy from the solution temperature, the constituents will separate into different crystal phases, forming a single microstructure. A eutectoid steel, for example, contains 0.77% carbon. Upon cooling slowly, the solution of iron and carbon, (a single phase called austenite), will separate into platelets of the phases ferrite and cementite. This forms a layered microstructure called pearlite. Since pearlite is harder than iron, the amount of softness achieveable is typically limited to that produced by the pearlite. Similarly, the hardenability is limited by the continuous martensitic microstructure formed when cooled very fast.
Hypoeutectoid alloys A hypoeutectic alloy has two separate melting points. Both are above the eutectic melting point for the system, but are below the melting points of any constituent forming the system. Between these two melting points, the alloy will exist as part solid and part liquid. The constituent with the lower melting point will solidify first. When completely solidified, a hypoeutectic alloy will often be in solid solution. Similarly, a hypoeutectoid alloy has two critical temperatures, called "arrests." Between these two temperatures, the alloy will exist partly as the solution and partly as a separate crystallizing phase. These two temperatures are called the upper (A3) and lower (A1) transformation temperatures. As the solution cools from the upper transformation temperature toward an insoluble state, the excess base metal will often be forced to "crystallize- out." This will occur until the remaining concentration of solutes reaches the eutectoid level, which will then crystallize as a separate microstructure. A hypoeutectoid steel contains less than 0.77% carbon. Upon cooling a hypoeutectoid steel from the austenite transformation temperature, small islands of ferrite will form. These will continue to grow until the eutectoid concentration in the rest of the steel is reached. This eutectoid mixture will then crystallize as a microstructure of pearlite. Since ferrite is softer than pearlite, the two microstructures combine to increase the ductility of the alloy. Consequently, the hardenability of the alloy is lowered.
Hypereutectoid alloys A hypereutectic alloy also has different melting points. However, between these points, it is the constituent with the higher melting point that will be solid. Similarly, a hypoeutectoid alloy has two critical temperatures. When cooling a hypereutectoid alloy from the upper transformation temperature, it will usually be the excess solutes that crystallize-out first. This continues until the concentration in the remaining alloy becomes eutectoid, which then crystallizes into a separate microstructure. A hypereutectoid steel contains more than 0.77% carbon. When slowly cooling a hypereutectoid steel, the cementite will begin to crystallize first. When the remaining steel becomes eutectoid in composition, it will crystallize into pearlite. Since cementite is much harder than pearlite, the alloy has greater hardenability at a cost in the ductility.
Effect Of Time And Temperature:-
Time-temperature transformation (TTT) diagram for steel. Proper heat treating requires precise control over temperature, the amount of time that an alloy remains at a certain temperature, and in the cooling rates of the particular technique. With the exception of stress-relieving, tempering, and aging, most heat treatments begin by heating an alloy beyond the upper transformation (A3) temperature. The alloy will usually be held at this temperature long enough for the heat to completely penetrate the alloy, thereby bringing it into a complete solid solution. Since a smaller grain size usually enhances mechanical properties, such as toughness, shear strength and tensile strength, these metals are often heated to a temperature that is just above the upper critical temperature, in order to prevent the grains of solution from growing too large. For instance, when steel is heated above the upper critical temperature, small grains of austenite form. These grow larger as temperature is increased. When cooled very quickly, during a martensite transformation, the austenite grain size directly affects the martensitic grain size. Larger grains have large grain-boundaries, which serve as weak spots in the structure. The grain size is usually controlled to reduce the probability of breakage. The diffusion transformation is very time dependent. Cooling a metal will usually suppress the precipitation to a much lower temperature. Austenite, for example, usually only exists above the upper critical temperature. However, if the austenite is cooled quickly enough, the transformation may be suppressed for hundreds of degrees below the lower critical temperature. Such austenite is highly unstable and, if given enough time, will precipitate into various microstructures of ferrite and cementite. The cooling rate can be used to control the rate of grain growth or can even be used to produce partially martensitic microstructures. However, the martensite transformation is time-independent. If the alloy is cooled to the martensite transformation (Ms) temperature before other microstructures can fully form, the transformation will usually occur at just under the speed of sound. When austenite is cooled slow enough that a martensite transformation does not occur, the austenite grain size will have an effect on the rate of nucleation, but it is generally temperature and the rate of cooling that controls the grain size and microstructure. When austenite is cooled extremely slow, it will form large ferrite crystals filled with spherical inclusions of cementite. This microstructure is referred to as "sphereoidite." If cooled a little faster, then coarse pearlite will form. Even faster, and fine pearlite will form. If cooled even faster, bainite will form. Similarly, these microstructures will also form if cooled to a specific temperature and then held there for a certain amount of time. Most non-ferrous alloys are also heated in order to form a solution. Most often, these are then cooled very quickly to produce a martensite transformation, putting the solution into a supersaturated state. The alloy, being in a much softer state, may then be cold worked. This cold working increases the strength and hardness of the alloy, and the defects caused by plastic deformation tend to speed up precipitation, increasing the hardness beyond what is normal for the alloy. Even if not cold worked, the solutes in these alloys will usually precipitate, although the process may take much longer. Sometimes these metals are then heated to a temperature that is below the lower critical (A1) temperature, preventing recrystallization, in order to speed-up the precipitation.
Techniques:- Complex heat treating schedules, or "cycles," are often devised by metallurgists to optimize an alloy's mechanical properties. In theaerospace industry, a superalloy may undergo five or more different heat treating operations to develop the desired properties. This can lead to quality problems depending on the accuracy of the furnace's temperature controls and timer.
Annealing Annealing is a rather generalized term. Annealing consists of heating a metal to a specific temperature and then cooling at a rate that will produce a refined microstructure. Annealing is most often used to soften a metal for cold working, to improve machinability, or to enhance properties like electrical conductivity. In ferrous alloys, annealing is usually accomplished by heating the metal beyond the upper critical temperature and then cooling very slowly, resulting in the formation of pearlite. In both pure metals and many alloys that can not be heat treated, annealing is used to remove the hardness caused by cold working. The metal is heated to a temperature where recrystallization can occur, thereby repairing the defects caused by plastic deformation. In these metals, the rate of cooling will usually have little effect. Most non-ferrous alloys that are heat-treatable are also annealed to relieve the hardness of cold working. These may be slowly cooled to allow full precipitation of the constituents and produce a refined microstructure. Ferrous alloys are usually either "full annealed" or "process annealed." Full annealing requires very slow cooling rates, in order to form coarse pearlite. In process annealing, the cooling rate may be faster; up to, and including normalizing. The main goal of process annealing is to produce a uniform microstructure. Non-ferrous alloys are often subjected to a variety of annealing techniques, including "recrystallization annealing," "partial annealing," "full annealing," and "final annealing." Not all annealing techniques involve recrystallization, such as stress relieving.[20].
Normalizing Normalizing is a technique used to provide uniformity in grain size and composition throughout an alloy. The term is often used for ferrous alloys that have been heated above the upper critical temperature and then cooled in open air
Stress relieving Stress relieving is a technique to remove or reduce the internal stresses created in a metal. These stresses may be caused in a number of ways, ranging from cold working to non-uniform cooling. Stress relieving is usually accomplished by heating a metal below the lower critical temperature and then cooling uniformly.
Aging Some metals are classified as precipitation hardening metals. When a precipitation hardening alloy is quenched, its alloying elements will be trapped in solution, resulting in a soft metal. Aging a "solutionized" metal will allow the alloying elements to diffuse through the microstructure and form intermetallic particles. These intermetallic particles will nucleate and fall out of solution and act as a reinforcing phase, thereby increasing the strength of the alloy. Alloys may age "naturally" meaning that the precipitates form at room temperature, or they may age "artificially" when precipitates only form at elevated temperatures. In some applications, naturally aging alloys may be stored in a freezer to prevent hardening until after further operations - assembly of rivets, for example, may be easier with a softer part. Examples of precipitation hardening alloys include 2000 series, 6000 series, and 7000 series aluminium alloy, as well as some superalloys and some stainless steels. Steels that harden by aging are typically referred to as maraging steels, from a combination of the term "martensite aging.
Quenching Quenching is a process of cooling a metal very quickly. This is most often done to produce a martensite transformation. In ferrous alloys, this will often produce a harder metal, while non-ferrous alloys will usually become softer than normal. To harden by quenching, a metal (usually steel or cast iron) must be heated above the upper critical temperature and then quickly cooled. Depending on the alloy and other considerations (such as concern for maximum hardness vs. cracking and distortion), cooling may be done with forced air or other gases, (such as nitrogen). Liquids may be used, due to their better thermal conductivity, such as water, oil, a polymerdissolved in water, or a brine. Upon being rapidly cooled, a portion of austenite (dependent on alloy composition) will transform to martensite, a hard, brittle crystalline structure. The quenched hardness of a metal depends on its chemical composition and quenching method. Cooling speeds, from fastest to slowest, go from polymer (i.e.silicon), brine, fresh water, oil, and forced air. However, quenching a certain steel too fast can result in cracking, which is why high-tensile steels such as AISI 4140 should be quenched in oil, tool steels such as ISO 1.2767 or H13 hot work tool steel should be quenched in forced air, and low alloy or medium-tensile steels such as XK1320 or AISI 1040 should be quenched in brine or water. However, most non-ferrous metals, like alloys of copper, aluminum, or nickel, and some high alloy steels such as austenitic stainless steel (304, 316), produce an opposite effect when these are quenched: they soften. Austenitic stainless steels must be quenched to become fully corrosion resistant, as they work-harden significantly. Tempering Untempered martensitic steel, while very hard, is too brittle to be useful for most applications. A method for alleviating this problem is called tempering. Most applications require that quenched parts be tempered. Tempering consists of heating a steel below the lower critical temperature, (often from 400 to 1105 ˚F or 205 to 595 ˚C, depending on the desired results), to impart some toughness. Higher tempering temperatures, (may be up to 1,300 ˚F or 700 ˚C, depending on the alloy and application), are sometimes used to impart further ductility, although some yield strength is lost. Tempering may also be performed on normalized steels. Other methods of tempering consist of quenching to a specific temperature, which is above the martensite start temperature, and then holding it there until pure bainite can form or internal stresses can be relieved. These include austempering and martempering.
Selective hardening Many heat treating methods have been developed to alter the properties of only a portion of an object. These tend to consist of either cooling different areas of an alloy at different rates, by quickly heating in a localized area and then quenching, or by thermochemical diffusion.
Differential hardening
A differentially hardened katana. The bright, wavy line, called the nioi, separates the martensitic edge from the pearlitic back. The inset shows a close-up of the nioi, which is made up of single martensite grains surrounded by pearlite. The wood-grain appearance comes from layers of different composition. Some techniques allow different areas of a single object to receive different heat treatments. This is called differential hardening. It is common in high quality knives and swords. The Chinese jian is one of the earliest known examples of this, and the Japanese katana may be the most widely known. The Nepalese Khukuri is another example. This technique uses an insulating layer, like layers of clay, to cover the areas that are to remain soft. The areas to be hardened are left exposed, allowing only certain parts of the steel to fully harden when quenched.
Flame hardening Flame hardening is used to harden only a portion of a metal. Unlike differential hardening, where the entire piece is heated and then cooled at different rates, in flame hardening, only a portion of the metal is heated before quenching. This is usually easier than differential hardening, but often produces an extremely brittle zone between the heated metal and the unheated metal, as cooling at the edge of this heat affected zone is extremely rapid.
Induction hardening Induction hardening is a surface hardening technique in which the surface of the metal is heated very quickly, using a no-contact method of induction heating. The alloy is then quenched, producing a martensite transformation at the surface while leaving the underlying metal unchanged. This creates a very hard, wear resistant surface while maintaining the proper toughness in the majority of the object. Crankshaft journals are a good example of an induction hardened surface.
Case hardening Case hardening is a thermochemical diffusion process in which an alloying element, most commonly carbon or nitrogen, diffuses into the surface of a monolithic metal. The resulting interstitial solid solution is harder than the base material, which improves wear resistance without sacrificing toughness. Laser surface engineering is a surface treatment with high versatility, selectivity and novel properties. Since the cooling rate is very high in laser treatment, metastable even metallic glass can be obtained by this method. USually the end condition is specified instead of the process used in heat treatment.
Case hardening Case hardening is specified by hardness and case depth. The case depth can be specified in two ways: total case depth or effective case depth. The total case depth is the true depth of the case. The effective case depth is the depth of the case that has a hardness equivalent of HRC50; this is checked on a Tukon microhardness tester. This value can be roughly approximated as 65% of the total case depth; however the chemical composition and hardenability can affect this approximation. If neither type of case depth is specified the total case depth is assumed. For case hardened parts the specification should have a tolerance of at least ±0.005 in (0.13 mm). If the part is to be ground after heat treatment, the case depth is assumed to be after grinding. The Rockwell hardness scale used for the specification depends on the depth of the total case depth, as shown in the table below. Usually hardness is measured on the Rockwell "C" scale, but the load used on the scale will penetrate through the case if the case is less than 0.030 in (0.76 mm). Using Rockwell "C" for a thinner case will result in a false reading.
Rockwell scale required for various case depths
Total case depth, min. [in] Rockwell scale
0.030 C 0.024 A
0.021 45N
0.018 30N
0.015 15N
Less than 0.015 "File hard"
For cases that are less than 0.015 in (0.38 mm) thick a Rockwell scale cannot reliably be used, so file hard is specified instead. File hard is approximately equivalent to 58 HRC. When specifying the hardness either a range should be given or the minimum hardness specified. If a range is specified at least 5 points should be given.
Through hardening Only hardness is listed for through hardening. It is usually in the form of HRC with at least a five point range.
CHAPTER 6- ELECTROPLTING Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal. Electroplating is primarily used for depositing a layer of material to bestow a desired property (e.g.,abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.) to a surface that otherwise lacks that property. Another application uses electroplating to build up thickness on undersized parts. The process used in electroplating is called electrodeposition. It is analogous to a galvanic cellacting in reverse. The part to be plated is the cathode of the circuit. In one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution called anelectrolyte containing one or more dissolved metal salts as well as other ions that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that comprise it and allowing them to dissolve in the solution. At the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they "plate out" onto the cathode. The rate at which the anode is dissolved is equal to the rate at which the cathode is plated, vis-a-vis the current flowing through the circuit. In this manner, the ions in the electrolyte bath are continuously replenished by the anode. Other electroplating processes may use a non-consumable anode such as lead. In these techniques, ions of the metal to be plated must be periodically replenished in the bath as they are drawn out of the solution.
PROCESS: Electroplating of a metal (Me) with copper in a copper sulfate bath The anode and cathode in the electroplating cell are both connected to an external supply of direct current — a battery or, more commonly, a rectifier. The anode is connected to the positive terminal of the supply, and the cathode (article to be plated) is connected to the negative terminal. When the external power supply is switched on, the metal at the anode is oxidized from the zerovalence state to form cations with a positive charge. These cations associate with the anions in the solution. The cations are reduced at the cathode to deposit in the metallic, zero valence state. For example, in an acid solution, copper is oxidized at the anode to Cu2+ by 2+ 2- losing two electrons. The Cu associates with the anion SO4 in the solution to form copper sulfate. At the cathode, the Cu2+ is reduced to metallic copper by gaining two electrons. The result is the effective transfer of copper from the anode source to a plate covering the cathode. The plating is most commonly a single metallic element, not an alloy. However, some alloys can be electrodeposited, notably brass and solder. Many plating baths include cyanides of other metals (e.g., potassium cyanide) in addition to cyanides of the metal to be deposited. These free cyanides facilitate anode corrosion, help to maintain a constant metal ion level and contribute to conductivity. Additionally, non-metal chemicals such as carbonates and phosphates may be added to increase conductivity. When plating is not desired on certain areas of the substrate, stop-offs are applied to prevent the bath from coming in contact with the substrate. Typical stop-offs include tape, foil, lacquers, and waxes.
Strike Initially, a special plating deposit called a "strike" or "flash" may be used to form a very thin (typically less than 0.1 micrometer thick) plating with high quality and good adherence to the substrate. This serves as a foundation for subsequent plating processes. A strike uses a high current density and a bath with a low ion concentration. The process is slow, so more efficient plating processes are used once the desired strike thickness is obtained. The striking method is also used in combination with the plating of different metals. If it is desirable to plate one type of deposit onto a metal to improve corrosion resistance but this metal has inherently poor adhesion to the substrate, a strike can be first deposited that is compatible with both. One example of this situation is the poor adhesion of electrolytic nickel on zinc alloys, in which case a copper strike is used, which has good adherence to both.
Electroless deposition Usually an electrolytic cell (consisting of two electrodes, electrolyte, and external source of current) is used for electrodeposition. In contrast, an electroless deposition process uses only one electrode and no external source of electric current. However, the solution for the electroless process needs to contain a reducing agent so that the electrode reaction has the form:
In principle any water-based reducer can be used although the redox potential of the reducer half-cell must be high enough to overcome the energy barriers inherent in liquid chemistry. Electroless nickel plating uses hypophosphite as the reducer while plating of other metals like silver, gold and copper typically use low molecular weight aldehydes. A major benefit of this approach over electroplating is that power sources and plating baths are not needed, reducing the cost of production. The technique can also plate diverse shapes and types of surface. The downside is that the plating process is usually slower and cannot create such thick plates of metal. As a consequence of these characteristics, electroless deposition is quite common in the decorative arts.
Cleanliness Cleanliness is essential to successful electroplating, since molecular layers of oil can prevent adhesion of the coating. ASTM B322 is a standard guide for cleaning metals prior to electroplating. Cleaning processes include solvent cleaning, hot alkaline detergent cleaning, electro-cleaning, and acid treatment etc. The most common industrial test for cleanliness is the waterbreak test, in which the surface is thoroughly rinsed and held vertical. Hydrophobic contaminants such as oils cause the water to bead and break up, allowing the water to drain rapidly. Perfectly clean metal surfaces are hydrophilic and will retain an unbroken sheet of water that does not bead up or drain off. ASTM F22 describes a version of this test. This test does not detect hydrophilic contaminants, but the electroplating process can displace these easily since the solutions are water-based. Surfactants such as soap reduce the sensitivity of the test and must be thoroughly rinsed off..
Effects Electroplating changes the chemical, physical, and mechanical properties of the workpiece. An example of a chemical change is when nickel plating improves corrosion resistance. An example of a physical change is a change in the outward appearance. An example of a mechanical change is a change in tensile strength or surface hardness which is a required attribute in tooling industry. THE CHEMISTRY OF COPPER PLATING
PURPOSE This experiment demonstrates the process of electroplating and a commercial method used to purify copper.
DESCRIPTION This experiment is most appropriate for a first-year college prep or AP class if done quantitatively. If done qualitatively, it would be appropriate for a general class. One of the most important applications of electrolytic cells is the process of electroplating, in which a thin layer of metal is deposited on an electrically conducting surface. In electroplating, the metal to be plated is used as the anode and the electrolytic solution contains an ion derived from that metal. In this experiment, a copper anode (US penny) will be used in a solution of copper sulfate. Copper will be plated out onto a second penny at the cathode.
TIME REQUIRED 30 minutes to set up; one period to complete.
MATERIALS Chemicals electrolyte solution (200 g CuSO4· 5H2O + 25.0 mL concentrated H2SO4 solution in enough distilled or deionized water to make l.00 L of solution)* pre-1983 pennies vinegar NaCl Equipment power supply (6.0-9.0 volts, 0.60-1.0 amps)* connecting wires with alligator clips 16-18 gauge copper wire 250-mL beaker* cardboard square (approx. 15 cm on a side) ammeter (optional) *See Modifications/Substitutions
HAZARDS Sulfuric acid can cause severe burns; handle with care. Goggles must be worn throughout this experiment. Although the power source is relatively weak, the electrodes and connecting wires should not be handled when the cell is operating. If a 9-V battery is used as the power source, it will become quite hot during use; caution should be exercised.
MODIFICATIONS/SUBSTITUTIONS 1. Copper(II) sulfate pentahydrate is available from garden supply stores as root eater. 2. Sulfuric acid is available from auto supply stores as battery acid. Substitute 95 mL of battery acid for 25 mL of concentrated sulfuric acid. 3. A battery charger or 9-V battery may be substituted for the power supply. If a 9-V battery is used, it will be nearly "dead" after completing the experiment. 4. A 16-oz plastic glass may be substituted for the beaker.
PROCEDURE 1. Pour 200 mL of the electrolyte solution into the beaker. 2. Attach connecting wires with alligator clips to the terminals of the power supply. 3. Clean the pennies with a mixture of 3 g NaCl and 15 mL vinegar; rinse and dry. 4. Tightly wrap one end of a 10-cm length of copper around each penny, leaving 5-6 cm of wire free. 5. Mass each penny-copper wire assembly and record the masses. 6. Push the free end of each wire through the cardboard square and place the square over the beaker so that the penny "electrodes" are immersed in the electrolyte solution as illustrated below. Note: the two electrode assemblies must not touch.
7. Attach the connecting wires to the top of the copper wire assemblies. 8. Allow the electroplating cell to operate for 30-60 minutes. Record the exact time the cell was operating (optional). 9. Record the ammeter reading from the meter or power supply (optional). 10.Remove each "electrode;" dry, being careful not to lose any of the copper plating; mass each and record. 11.If an ammeter reading is taken, calculate: a. the number of coulombs of charge passed through the electrolytic cell, b. the theoretical number of moles of copper that should have plated out, c. the actual number of moles of copper that plated out, and d. the % yield of copper. 12.If an ammeter is not used, calculate: a. the number of moles of copper removed from the anode, b. the number of moles of copper added to the cathode, c. the % of copper conserved, d. the number of coulombs of current necessary to plate out the moles of copper calculated in step 12b, and e. the average current that must have passed through the cell.
DISPOSAL Pennies used in this experiment should not be reused as currency. Solids may be discarded with other solid waste. Electrolyte solution should be stored for re-use; if it becomes necessary to dispose of the solution, it should be flushed down the drain with plenty of water.
DISCUSSION As copper is plated out at the cathode (negative electrode), copper goes into solution at the anode (positive electrode) as copper(II) ions, maintaining a constant concentration of copper(II) ions in the electrolytic solution. cathode: Cu2+(aq) + 2 e- Cu(s) anode: Cu(s) Cu2+(aq) + 2 e-
Commercial plating is done very slowly in order to obtain a smooth, even coating of the plated metal. Although this experiment does not produce plating of commercial quality, it gives students the opportunity to study the chemistry of an important commercial process. This general method is also used in purifying copper. A small cathode of pure copper is used with a larger anode of impure copper. As the electrolytic cell operates, pure copper is transferred to the cathode.
If an ammeter reading is not taken, students can compare the changes in mass of the two electrodes and from the number of moles of copper plated, calculate the number of coulombs of charge passed through the cell and the average current through the cell.
TIPS If power supplies or batteries are not available in sufficient supply to allow students to do this as an experiment, it may be done as a demonstration. In such a case, it may be desirable to carry out the electrolysis in a 1-L beaker or large, wide-mouth jar and use small pieces of copper pipe or small copper plumbing fittings (available from a hardware store) to make the demonstration more visible to students.
BIBLEOGRAPHY:-
1) www.yamaha-motor-india.com
2) www.wikipedia.com
3) Auto Car Magazine
4) Test Drive Magazine
5) Velocity Magazine
6) www.google.com