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Transcript
1 LEARNING GUIDE Week No.: __1...
1 LEARNING GUIDE Week No.: __1__ TOPIC: Introduction to Machine Shop Trade I. EXPECTED COMPETENCIES Upon completing this Learning Element, you should be able to: 1. Recall learning‟s about the trades and professions in the field of manufacturing 2. State the importance of Ergonomics to human daily lives. 3. Able to illustrate the basic engineering principles applied to explain structure, properties and applications of materials II. CONTENT/TECHNICAL INFORMATION INTRODUCTION TO MACHINE SHOP TRADE There are many divisions in the Machine Shop Trade. One of this division in the grouping of machines, division in the skills required of machine operators and division in the types of shops where the work is done. These shops can be divided into three groups namely; Job Shop, Limited- production Shops and Mass-Production Shops. WHAT IS A JOB SHOP? A job shop is a machine shop that is equipped with machine and workers that can undertake a wide range of machining jobs of limited quantity and usually of a very specialized nature. (In this case the word “Job” refers to the product that has to be made and not the fact that a worker is employed). A job shop may be called upon to developed to prototype of an idea through up by a design engineer or an inventor. It may be employed to make a single piece or a dozen or a hundred of pieces in a standard or a special shape. A job shop is often used to repair machinery of for manufacturers who do not have a mechanical maintenance department. Spaced is frequently an important factor in work of this kind, and overtime work is often to complete the work on schedule. WHAT IS LIMITED-PRODUCTION SHOP? A limited production shop falls between a job shop and mass production shop. It specializes in producing identical parts in limited quantities ranging from one hundred to several thousands. Machine tools used in limited production shops, have been using automatic and numerically controlled machine tools. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 2 WHAT IS A MASS PRODUCTION SHOP? This is shop where parts are manufactured in vast numbers. Automatic and numerically controlled machine are fully utilized. Machines are set up to perform several operations with different cutting tools. Quite often the work is positioned and repositioned by mechanical arms thus enabling one operator to attend to several machines. These shops have their own numerical controls systems, programming computers and tape making department. Types of shops: The Production Shop – is the place where finished parts and products are manufactured in quantity. It is the usually a very large concern in which all types of machine tools are used. Many of the machines are automatic. The production shop employs men with varying qualifications. These include many machine operators, machinists, tool-and-die makers, layout men, engineers, tool designers, and other tradesmen with related skills. A Job Shop – is a small shop which dies, tools, fixtures, and small quantities of one part are made. The basic machine tools are used mostly by all-around machinists and tool-and-die makers. PLANT LAY OUT Plant lay-out embraces the physical arrangement of industrial facilities. This arrangement installed or in plan, includes spaces needed for material movement, storage, indirect laborers, and all other supporting activities or services, as well as for operating equipment and personnel. When we use the term “Plant Lay-out” sometimes we mean the exiting arrangement, sometimes the proposed new lay-out, and often we mean the actual installation, a plan or job. However, the term is so frequently used that seldom we confuse the meaning. The work of lay-out planning covers a wide range. It may involve only one involve only one individual workplace, or it may include the complete arrangement of many acres of industrial property. But in either case, we must plan it, if it is to be a good lay-out. OBJECTIVES OF GOOD PLANT LAY-OUT Generally speaking, we are after an arrangement of work areas and equipment that will be the most economical to operate and yet safe and satisfying for employees. In terms of the elements of production we want an arrangement of productive men, material, machine, and their support activities that will let us produce a product at a cost This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 3 low enough for us to sell at a profit in a competitive market. More specifically, the advantage of a good lay-out result through savings in operating costs. Such reduced cost from the following: 1. Reduced risk to health and safety of employees- any lay-out that makes convenient for workers to leave the tools in the aisles, that requires them to work past unprotected furnaces, or chemical vats, or that calls for unstable stacks of material –in-process should be re-examine to correct these hazards. 2.Improved morale and workers satisfaction- workers want to work in plant that is well laid out. One fine new foundry seemed just perfect. But the molders complained of facing bright sunny windows and working in the shadows of their molding machines. 3.Increased Output- usually better lay out will give greater output with the same or less cost, fewer, man- hours and reduced machine hours. 4.Fewer production delays – balancing out operation out times and department loads is part of a plant ay-out. When operations that take about at the same time can be arranged, he occasion \s when material – in-progress needs to stop be almost eliminated. By never “letting part touch the floor” one plant assembling diesel engines cut out all delays from 24 to 11. In number. 5.Saving Floor Space – (Production, storage, and service areas) idle aisles, waiting material, excess distances between machine, awkward placing power outlets or washroom, and spreading out stocks bins only one level high all take added floor space. Good lay-out uncovers this waste and tries to correct them. One shipyard arranged its erection ways to produce 28 percent more ships in the same yard by a simple change in lay-out. 6.Reduced Material Handling – One plant that set-up an assembly line for stove ovens reduced handling to nothing by passing the ovens between operations, transport existed to and away from the line. Many stamping shops have rearranged their presses so that workers can pass work from one row directly to next. This change eliminates a transport for each machine tied together in this way. 7.Greater utilization of machinery, manpower and services – this is a question of cost. When labor cost is high, you want manpower utilization. A plant making electric motors founds its conveyor installation could be made could be made to carry more items. By rearranging the feeding – on and taking- offs points, the conveyor doubled its utilization at no added cost. 8.Reduced inventory in process – while this is in part a production control problem, good lay-out can do a great deal on this also. Whenever it is possible to keep material moving from one operation directly to another, material moves through the plant faster reduced that amount of the material process. This comes about chiefly through reducing delays of waiting material. By relocating departments on that they had the proper relation to each other; one plastic produced reduced its inventor in process by more than 35 percent. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 4 9.SHORTER MANUFACTURING TIME – by shortening distance and reducing idle materials in delays and unnecessary stoppages, the time for material to move through the plant is shortened. One factory eliminated all temporary stoppage points and forced parts to keep moving. 10. REDUCED CLERICAL WORK and INDERECT LABOR – when it‟s possible to lay-out the plant so as keep material moving more or less automatically, production, scheduling and dispatching can be reduced greatly. 11.EASIER CONGESTION AND CONFUSION – lay-out can affect the ease and quality of supervision. A mezzanine office where a foreman can look down the floor is one type of time saving for supervision. Other types pertain strictly to the location and arrangement of workstations. With workplace in direct sequence, the supervision can check easily on the work coming through, even though the workplace are jumbled and the place are at odd angles. 12. LESS CONGESTION AND CONFUSION – delays of material, unnecessary movements or handling and intersects transport paths all cause confusion and congestion. By moving materials directly and keeping them moving, one press shop reduces its labor cost by 40 percent and eliminated practically all confusion and congestion. 13. REDUCED HAZARD TO MATERIAL OR ITS QUALITY – good layout can be very effective in reducing hazards. One manufacturer found his drop-forged shop right next to his expensive tool room. Vibration and dirt in each case damaged the material in the nearby department. New layouts separated the activities and reduced the hazards to the materials. 14. EASIER ADJUSTMENTS TO CHANGING CONDITIONS – one company located its new power plant in a convenient central location at one end of the plant. Two years later it wanted to expand its foundry and machine shop. Since the site was barred by the river other departments and the power plant, the company was forced o locate the plant expansion at an entirely different site. 15. MISCELLANEOUS OTHER ADVANTAGES – good layout may result in many other advantages, easier and better control of cost, easier maintenance of equipment, more workers able to go on incentive work areas, neater appearance of the work areas, or more sanitary condition of work area. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 5 SAFETY IN SHOP LAYOUT In planning a machine shop layout or revising existing layouts to meet the safety standards, the following areas should be considered. 1] Machine tools should be arranged with ample working space so that the operator has ample room to safely operate the machine, perform routine maintenance and check all controls. 2] Aisles and passageways must be wide enough for free access to the machine and in and out of the shop. Aisles should not be less than 3 feet wide. Lanes for aisles and passages ways should be painted in white or black. 3] Firefighting equipment should be properly identified and located where it can be seen from any part of the shop. 4] Provision should be made for First Aid Cabinet, for minor scratches and cuts. Records should be kept of these minor accidents. 5] Noise level should comply with the Occupational Safety and Health Act (OSHA) standards. POINTERS FOR PLANNING MACHINE SHOPS 1] Heavy duty machines should be placed as close as possible to the entrance through which castings and other heavy materials received. These machines should be serviced by a swing crane or other lifting apparatus. 2] In the installation of any machine provisions should be made to permit moving small truck up to it for the purpose of unloading jigs, fixtures, or pans of materials. 3] Enough space should be provided between machines to prevent the operator from getting in the way of one another. 4] The need for accuracy demands the maximum use of light in a machine shop. If the general lighting at each workstation is insufficient to ensure accurate work, supplement light should be provided. 5] Lathes located near the windows should be turned at an angle of 60 to 45 degrees to the wall with the light from the windows falling along the bed illuminating the headstock. The light should come from the right front of the operator. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 6 6] If the walls are painted with reflecting type of light-colored paint, this will add to the efficiency of the lighting. 7] A suitable space should be provided for the disposal of metal shavings and scrap. 8] Power hacksaws should be located near the stock rack so that long stock may be sawed with a minimum of handling. Careers in Machine Shop: The foundation of every production line is the precision machinist or tool-and-die maker. Machine tools make mass production possible. It takes a great many people to design, build, and operate these machines. Whether the product is a small metal toy, or a new car manufacturing depends on the skill of the machinists who makes it. These are approximately three-quarters of a million people who work directly as machinists or machine operators. These are several million more that can profit by knowledge of machine shop. Trades and Profession: A trade is a job requiring great skill and knowledge. Usually from 2 to 5 years of special training are needed. A profession requires formal education, at least bachelor‟s degree. Between the trade and the profession is a new group called These are people who have had the equivalent of a trade education in science, mathematics and business related to that area of work. The skilled tradesman (machinists, for example) performs highly skilled work. Technicians do the work that ranges between that of the engineer and the skilled tradesman. Technician‟s job depends on the industry or the particular product that is being manufactured. Summary of what is the difference between technicians and technologists? 1. A technician and a technologist differ in their educational levels and responsibilities. 2. A technician is just a person with a practical understanding of technology. On the other hand, a technologist is a person who is completely aware of various technologies. 3. A technologist has a greater role than a technician; a technician works under a technologist. 4. A technologist will have an engineering degree, whereas, a technician will have a lower degree, or diploma certificate. 5. A technologist has a wider range of duties when compared to a technician; his position is above the technician‟s position in technological matters. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 7 6. A technologist is solely responsible for innovative ideas, and the technician is responsible for the application of those ideas. 7. Unlike technicians, technologists handle most of the more complex work. Opportunities in the skilled trades: 1. Machine Tool Operator – is a semiskilled person who can operate only one machine or do only a few operations. His job is routine one. He does the same thing repeatedly every day. 2. The all-around machinists – is one who can set up and operate all the machine tools. He must be able to read prints, use precision measuring tools, and make adjustments. He is a highly skilled worker who might be employed in a small job shop, in the tool room of a large manufacturing concern, or in a large production shop. 3. Tool-and-die makers – are highly skilled machinists. They design, make, and repair the tools, dies, fixtures, and jigs that are used in the manufacture of all types of products. The toolmaker must have qualifications that make him the best of the skilled metalworkers, above all others in the plant in prestige as well as pay. 4. Lay-out men – are skilled machinists who read prints and transfer measurements to metal. These are the men who get the parts ready to be machined. They must know mathematics. They must also know how to read blueprints and use precision measuring devices. 5. Setup men – are skilled machinists who get the machines ready (do the set ups) for the machine operator. They must be able to sharpen cutting tools, set and adjust the machine, and check it to make sure it will make the part exactly as shown on the print. 6. Inspectors – are trained to use all types of precision measuring tools and gages to check finished work pieces for accuracy. 7. Foremen and Supervisors – are the skilled machinists who have been promoted to positions of responsibility. They supervise the work of other men in the shop. Two main types of technician: 1. Engineering Technician – is the part of the engineering field which requires the application of the scientific and engineering knowledge and methods combined with technical skills in support of engineering activities. 2. Industrial Technician – exhibits similar competences within a narrower range of industry in such areas as drafting, tool-and-die design and machine tools. Ergonomics (1969) – defined as the study of the reaction between man and his occupation, equipment and environment. Ergonomics is the science of designing the job, equipment, and workplace to fit the worker. Proper ergonomic design is necessary to prevent repetitive strain injuries, which can develop over time and can lead to long term disability. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 8 The International Ergonomics Association defines ergonomics as follows: Ergonomics is employed to fulfill the two goals of health and productivity. It is relevant in the design of such things as safe furniture and easy-to-use interfaces to machines. Overview Ergonomics is concerned with the „fit‟ between people and their technological tool and environments. It takes account of the user‟s capabilities and limitations in seeking to ensure that tasks, equipment, information and the environment suit each user. To assess the fit between a person and the used technology, ergonomics consider the job (activity) being done and the demands on the user; the equipment used (its size, shape, and how appropriate it I for the tasks), and the information used (how it is presented, accessed, and changed). Ergonomics draws on many disciplines in its study of humans and their environments. Typically, an ergonomist will have a BA or BS in Psychology, Industrial/Mechanical Engineering or Industrial Design or Health Sciences, and usually an MA, MS or PhD in a related discipline. Many universities offer Master of Science degrees in Ergonomics, while some offer Master of Ergonomics or Master of Human Factors degrees. In the 2000s, occupational therapists have been moving into the field of ergonomics and the field has been heralded as one of the top ten emerging practice areas. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 9 III. PROGRESS CHECK A. ESSAY: Discuss briefly the following principle. 1. Name four skilled divisions in the machine shop trades. Tell what each requires? 2. Explain the differences between job shop, production shop & mass-production shop. 3. What is a basic difference between mechanization and automation? 4. Give at least 5 objectives of a good plant lay-out. 5. List at least 3 pointers for planning machine shop. 6. Why should a consideration of Ergonomics be included in planning a machine shop lay-out? 7. What is the difference between a jig and a fixture? 8. What is a technologist? Describe what kind of work he does? IV. REFERENCES Felker C, A., Bradley. J.G. (1976). Burghardt, H.D., Axelrod, A., & Anderson, J. (1959) McGraw-Hill, Inc. DeGarmo, E.P., Black, J.T., & Kosher, R.A. (1988). Macmillan Publishing Company, New York. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 10 This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 11 LEARNING GUIDE Week No.: __2__ TOPIC Material Selection Gear Speeds (Simple & Compound Gearing) I. EXPECTED COMPETENCIES Upon completing this Learning Element, you will be able to: 1. Describe the gearing arrangement inside the quick-change gear box. 2. Compute the necessary data needed on a given gearing arrangement. 3. Determine the RPM for different materials and diameters. 4. Identify what certain material based on the various standard coding of metal. II. CONTENT/TECHNICAL INFORMATION Material selection is a step in the process of designing any physical object. In the context of product design, the main goal of material selection is to minimize cost while meeting product performance goals. The fact is material selection is so important because engineers have to plan for any potential consequences that certain materials may present. In the long run, this will make the process of engineering design analysis easier and give the project the best chance of success The objective of any practical work dealing with the manufacture of products is to produce components that will adequately perform their designated tasks. If we This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 12 recognize that the term engineering materials includes virtually all metals and alloys, ceramics, glasses, plastics, elastomers, electrical semi-conductors, concrete, composite materials, and others. Iron is the fourth most plentiful element in the earth‟s crust and, for centuries has been the most important of the basic engineering metals. Metals and Alloys Metals are one of the nature‟s most common elements. Iron, copper, and aluminum are some examples. An is a mixture of two or more metals. Usually it consists of a base metal (the largest part of the alloy) and a smaller amount of other metals. Brass, for instance, is an alloy of copper (the base metal) and zinc. Steel is an alloy of iron and carbon. In the machine shop, metals and alloys are usually called. Metals are divided into two groups, the which contain a large percentage of iron and the , which contain no iron. Properties of Metals The most important characteristics of metal are its , , and. 1 is the ability of a material to resist applied forces. 2. is the ability of the material to resist penetration and abrasion. 3. is the ability to spring back to original shape. is the ability to undergo permanent changes of shape without rupturing is the ability to absorb mechanically applied energy. Strength and ductility determine a material‟s toughness. Magnetic properties of metals are those which have to do with reactions to magnetic or electric forces. Some metals are attracted to magnets, some are not. Certain high-carbon and alloy retain magnetism and are used to make permanent magnets. The magnetic properties of a metal often determine whether the metal can be used in a particular situation. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 13 hemical properties of metal pertain to its resistance to corrosion and oxidation. The melting temperature of a metal also falls into this category. Chemical properties often determine a metal‟s suitability for a specific purpose. Iron and Steel is one of the basic elements in manufacturing. Steel is an alloy of iron and carbon. Steels are grouped as , , etc.. The amount of carbon is given in points (100 points equal to 1 percent) or as a. Alloy steels include, in addition to iron and carbon, one or more other elements. These are added in order to impart a wanted quality to the metal. Steels are classified in two ways, How steel is manufactured Steel production is one of the largest and most important industries in the United States. More than 3 billion tons of steel have been produced in this country in the past 100 years. The iron ore used to make steel comes from open pit and underground mines. It is moved by boat to steelmaking centers located chiefly in Indiana, Ohio and Pennsylvania. At these centers, the iron ore is transformed into a variety of kinds and grades of steel. The blast furnace is basically a huge steel shell, lined with firebrick. Some are almost as high as a ten-story building. Ore processing begins in the blast furnace. A mixture of iron ore, coke, and limestone is first brought t the top of the furnace and dumped into it. This mixture is called the. Air that has been dried and heated to about 1250˚F is then blown into the furnace near its base. As the coke burns in this air it generates heat and gases which melt the charge. Impurities in the charge are absorbed by the limestone and form a substance known as The temperature at the base of the furnace rises to approximately 3500˚F and the iron and slag in this area become liquefied. Since molten slag is lighter than the molten iron, it floats on top of the iron. or removing the molten iron from the furnace is done every 4 or 5 hours. From 150 to 300 tons of pig iron (the type of iron produced in the blast furnace) can be drawn off at a time. It is interesting to note that it takes This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 14 almost 2 tons of ore, 1 ton of coke, nearly ½ ton of limestone, and a little less than 4 tons of air to make just 1 ton of pig iron. The molten pig iron that is tapped from the blast furnace still contains some impurities. To change pig iron into steel, these impurities must be removed. This is done in one of three kinds of furnaces: , , or This furnace is used to convert molten pig iron, iron ore, and scrap iron into steel. Between 8 and 12 hours of intense heat are required before purified molten steel can be run from the furnace into a ladle. In this furnace, 80 tons of scrap and molten iron are changed into steel in just 40 to 60 minutes. Oxygen, blown into the furnace at high speed, burns out the impurities. This furnace is used to produce high grade carbon and alloy steels. Powerful electric currents are sent through three large rods (electrodes) that pass through the top of the furnace. Steels can be classified into five groups, , , , , and. Here are some things you should know about steels. a. Low-carbon steel contains from 0.04 to 0.30 percent of carbon (4 to 30 points). This steel does not contain enough carbon to be hardened. It can be heat-treated, however. It is used for projects and product in which an easily worked metal is needed. These are sometimes called soft or mild steels. Low-carbon steel is easily welded, machined, and formed. b. Medium-carbon steel has from 0.30 to 0.60 percent of carbon. A ton of medium-carbon steels contain 60 to 120 pounds of carbon. It is used for many standard machine parts such as bolts, nuts, and screws. c. High-carbon steel contains from 0.60 to 1.70 percent of carbon. It is used for items that must be hardened or tempered. High-carbon steel is sometimes called carbon tool steel. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 15 The automobile contains about 100 different kinds of alloy steel. Each alloy steel has a “personality” all its own. Most steels contain some carbon, phosphorus, sulfur, silicon. Alloy steels also contain very small quantities of other elements. Common Alloying Elements is added to increase strength and toughness. It also helps to prevent the steel from rusting. adds hardness, toughness, and resistance to wear. Gears and axles are often made of chrome-nickel steel because of the greater strength in this steel. is used in steel to produce a clean metal. It is also adds to the strength of the metal and helps in heat treating. is used to make steel more elastic. Springs are made of silicon steel. is combined with chromium, vanadium, molybdenum, or manganese to produce high speed steel used in cutting tools. is used to add toughness and higher strength to steel. Some high-speed cutting tools are made from molybdenum steel. improves the grain of steel. It is used with chromium to make chrome-vanadium steel. This type of steel is very strong and has excellent shock resistance. Gears and shafts are often made of chrome-vanadium steel. is added to intensify the degree of hardening (the depth to which the steel cab be hardened by heat treatment). is used in magnet steels and permanent-magnet alloys, in special alloys for severe high-temperature service, and for tool steels that hold a cutting-edge at high temperatures. Cobalt steel is also used to put a hard surface on parts of equipment that must resist wear. is added to increase the strength of some of the super alloys that are used in high-temperature service. Columbium is also added to prevent undesirable changes in the structure of certain grades of stainless steels when they are used at high temperatures or welded. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 16 may be added to some grades in some amounts, usually under 0.5 percent, to retard rusting. Copper is added to steel as pure metal or as copper bearing scrap. is added to prevent undesirable changes in the structure of some stainless and heat-resisting steels when they are used at high temperatures or welded. Titanium is also used as an alloying element to increase the strength of some of the super alloys for severe high-temperature service. 3. Stainless steels are those that contain from about 10 percent to 26 percent chromium. Nickel is often added to assure better corrosion resistance. The 18-8-type (18 percent chromium, 8 percent nickel) is widely used in soda fountains, steam cooking, and pasteurizing equipment. These steels, which include the high-speed steels, contain considerable amounts of alloying elements such as tungsten, molybdenum, cobalt, manganese, and chromium as well as a normal amount of carbon. When brought to their particular hardening heat, these alloy steels by cooling in air. They are the most widely used steels in the cutting industry. All have the ability to retain hardness and toughness at elevated temperatures. Unlike carbon tool steels, tool-and-die steels can cut while dull red (in the neighborhood of 1000°F), without loss of hardness. The higher the cobalt content the greater the red hardness factor, thus allowing the tool to be used at higher cutting speeds. CAST IRON Cast iron is used in heavy part of many machines. It is the most common material used in making castings. Cast iron is low in cost and wears well but is very brittle and cannot be hammered or formed. It contains from 24 percent of carbon. The basic kinds of cast iron are white iron, gray iron, and malleable iron. is a particular kind of cast iron that has been made more malleable by an annealing procedure (heated to a high temperature, then slowly cooled). Malleable-iron castings are not so brittle or as hard as cast iron. They have a harder outer surface and a softer interior. They can stand a great This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 17 deal of hammering. is a kind if cast iron that has even more desirable qualities to withstand shock, blows, and jerks. ROLLED STEELS Steel bars, steel rods, and steel beams are produced by rolling the steel into these shapes. The steel is squeezed into shape, much as clothes are squeezed through a wringer. are formed into shape while the metal is red hot. The metal goes through the series of rollers, each a little closer together. As the steel comes through the last rollers, hot water is sprayed over it, forming a. These steels is fairly uniform in quality hot-rolled bars are used to produce cold-finished steels. are used when great accuracy, better surface finish, and certain mechanical properties are needed. There are two procedures that result in what is called. The of drawing the bars through a series of dies, each a few thousandths inch smaller than the preceding one. is where steel is rolled cold to the exact size. IDENTIFYING STEELS There are three methods of identifying steels: Number systems for identifying carbon and alloy steels have been developed by the Society of Automotive Engineers (SAE) and the American Iron and steel Institute (AISI). The system is based on the use of numbers composed of four or five digits. a. The first digit tells the kind of steel: 1 show carbon steels, 2 is nickel steel, 3 is nickel-chromium steel, 4 is molybdenum steel, etc. b. The second digit in alloy steels shows the approximate percent by weight of alloy elements. For example, 2320 shows a nickel steels with about 3 percent nickel The American Iron and Steel Institute has also developed a system for indicating the kind of furnace in which the steel was made This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 18 Most manufacturers paint each different kind of steel a different color. Some paints only the end. Others paint all along the bar. This is done to keep from confusing the steel bars in the steel racks. Is a certain steel is painted red, it may mean that it is a high-carbon steel. Each company has a different color code. Low-and-medium-carbon steels are not identified in this way. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 19 This method of identification rather inaccurate. The test is made by observing the sparks given off when the metal is ground. The kind, frequency, position, and color of the sparks are all considered COMMON KINDS OF STEELS a. SAE-AISI C1018. This is a low carbon; general-purpose steel that is used for hammer forging. It can be case hardened. It is made in open-hearth furnace. b. SAE-AISI C1035. This is intermediate-carbon steel. It is higher in strength and hardness than low-carbon steel. It might be used for studs, bolts, and shafts. c. SAE-AISI 1045. This is higher-carbon machinery steel that can be used for projects or parts that require great strength and hardness. This steel can be forged. Used for machinery parts like screwdrivers, is, hammerheads, vise parts. d. SAE-AISI 1095. This is a high-carbon spring steel. It is less expensive material that maybe used to make parts for later hardening and tempering. A.SAE-AISI 1018. This is a low-carbon steel made by the open-hearth method. It is good for projects that must be brazed or welded. b. SAE-AISI 1042. This is a medium-carbon steel made in the openhearth. It can be used for projects requiring a good deal of strength. a. SAE-AISI w 2-1.00 carbon. This is an all-purpose, water-hardening carbon tool steel with a small amount of vanadium. Best to use because of excellent hardness. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 20 Gear Speeds The flat and vee type belts used on modern machinery are readily replaced by maintenance who are guided by manufacturer‟s recommendations in regard to such factors as size and maximum speed. Belts now are rarely spliced, unless they are of special length or size. They are replaced by new ones, in the interest of saving time. Gears are a better device for providing driving power or traction especially where heavy loads must be overcome. Knowledge of the speed of gears in mesh is knowledge that most machinists, auto mechanics, engineers, and inventors require at one time or another. Whenever a machinist sets a certain number of revolutions per minute or feed rate on a machine, he is choosing a combination of gears that will give him the desired results. A belt running around a pulley can slip. If the belt is replaced by teeth and the pulleys are brought together in mesh, the slippage is eliminated. Thus, we think of a gear as a pulley with teeth on its rim, the calculation of gear speeds becomes simple. Example Two gears in mesh have 20 and 30 teeth. If the 20-tooth gear rotates at 150 rpm, what is the speed of the larger gear? TxS=txs txs 20 (150) Transposing, S = ---------- = --------------- = 100 rpm T 30 Simple Gearing In a simple gear train, two or more gears are in mesh, but each gear in the train is on a. In such a train, the first gear in the train is the driver (D) and the last is the driven gear (d).. Hence, the formula applies to a simple gear train. If a simple gear train is composed of two meshing gears, the relationship of the number of teeth and the speed of the gears is given by the basic speed formula The inverse proportion between the speeds and number of teeth is clearly illustrated by the following example. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 21 Example Suppose two gears with 36 and 48 teeth are meshed and the speed of the 36tooth gear is 300 rpm. Find the speed of the 48-tooth gear. TxS 36 x 300 s = ---------- = --------------- = 225 rpm t 48 The inverse ratio of the speeds is 225/300 and the ratio of the number of teeth is 36/48. These two ratios are equal. However, it should be noted that they are equal only when the speeds of both gears are compared by an inverse ratio. It frequently happens that motion must be transmitted by gears from one shaft to another when the shafts are too far apart for the gears to mesh. Large gears might span the distance between shafts, but large gears take up space. Use of large gears can be avoided by the use of one or more idlers. An idler gear does not affect the speed of the driver (the first gear in a simple train) or the driven gear (the last gear in a simple train) When two gears are in mesh, they rotate in opposite directions. In the figure 1, two idlers are placed between the driver A and the driven gear D. These two idlers will cause the driver and the driven gears rotate in opposite directions but will not affect their relative speeds. A B C D In computing the number of teeth or speed of the driver or driven gear in a simple gear train, disregard all idler gears. In the determination of the direction of rotation of driver or driven gear, the idler gears must be considered. Idler gears are both driver and driven gears. Too much emphasis is traditionally placed on the direction of rotation of gears in a gear train. What is often overlooked is the fact, that if the driven gear does not This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 22 rotate in the desired direction, a reversing switch on the electric driving motor will solve the problem. Compound Gearing In a compound gear train, and, as a result, one is driven and the other is driver. Compound gearing is used to reduced space and obtain speeds that would be impossible with simple gearing. A Figure 2 represents a compound gear train. Gears B and D are keyed on the same shaft. If gear A is the driver in the compound gear train, D is a driven (shaded) gear; since B and D are keyed to the same shaft, B is a driver and C is a driven (shaded) gear. Product of all driving teeth x RPM of the first driving gear RPM of final driven gear = ------------------------------------------------------------------ Product of all driven teeth Example In the compound gear train shown in the figure 2, compute the speed of C if the driver A rotates at 300 rpm. The first driver is A and the second B; the first driven gear is D and the second, or last, is C. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 23 300 x 24 x 64 RPM = ------------------ = 640 20 x 36 III. PROGRESS CHECK A. Choose the correct term that corresponds to each question, write the letter on the space provided. _____ 1. Alloy that improves strength of steel at high temperature application. A. tungsten C. chromium B. manganese D. silicon _____ 2. All are associated with standard material specification except A. American Iron & Steel Institute C. Southeast Asia Iron Institute B. Society of Automotive Engineers D. American Society for Testing Materials _____ 3. All are associated with the grade of steel except A. SAE 43XX C. SAE 10XX B. SAE 13XX D. SAE 74XX _____ 4. Most effective alloying element for reducing brittleness of steel at very low temperature A. manganese C. silicon B. molybdenum D. nickel _____ 5. It has molybdenum alloy except A. SAE 43XX C. SAE 8XXX B. SAE 41XX D. SAE 5XXX _____ 6. The cheapest and the most abundant engineering material. A. Steel C. Cast Iron B. Aluminum D. Babbitt _____ 7. Which of the following is not a kind of cast iron A. gray iron C. lead iron B. white iron D. malleable iron _____ 8. Stainless steel is obtained principally by the use of which alloying elements? A. Chromium C. Carbon B. Nickel D. Tungsten _____ 9. Manganese steel standard designation A. 13XX C. 11XX B. 10XX D. 8XXX _____ 10. Plain carbon steel standard designation A. 6XXX C. 10XX B. 13XX D. 2XXX This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 24 _____ 11. The maximum hardenability of any steels depends on A. The carbon content C. The chemical composition B. The grain size D. The alloying elements present _____ 12. Is a mixture of two or more metals. A. Metal mixture C. Alloy B. Combination of metal D. Bronze _____ 13. The last two (and sometimes three) digits show the ______________. A. % alloying element C. kind of steel B. Carbon content D. kind of furnace _____ 14. The letter is often placed before (as a prefix) the number of the steel indicating the kind of furnace in which the steel was made, Prefix B is ____________. A. Basic open-hearth alloy steel C. Basic open-hearth carbon steel B. Acid Bessemer carbon steel D. Electric-furnace steel B.Problem Solving: Read, Analyze and Compute what is being aske 1. A 20-tooth gear turning at 200 rpm drives a gear with 40 teeth. What is the speed of the driven gear? 2. A driver gear with 24 teeth rotates at 400 rpm, and the gear with which it meshes is to rotate at 300 rpm. How many teeth must the driven gear have? 3. Driver and driven gears are required to rotate at 400 and 500 rpm, respectively. The gears available have the following number of teeth: 20, 24, 30, 36, 40, 48, 50, 56, 60, 64, 70, 72, 80, and 84. Find the pairs of gears which give the required speed ratio. 4. In the compound gear train shown in the figure, the gear A is the first driver and rotates at 200 rpm. What is the speed of the 40-tooth gear? 5. In the figure below, gear A is the first driver in the compound gear train. If gear A makes one revolution, how many revolutions will gear B make? This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 25 IV. REFERENCES Burghardt, H.D., Axelrod, A., & Anderson, J. (1959) McGraw-Hill, Inc. DeGarmo, E.P., Black, J.T., & Kosher, R.A. (1988). Macmillan Publishing Company, New York. Shiksha, S. (2020). Workshop Practice. Retrieved July 08, 2020 from http://ecourseonline.iasri.res.in/mod/page/view.php? This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 26 LEARNING GUIDE Week No.: __3__ TOPIC Theory of Metal Cutting Lathe Cutting Tools Lathe Theories and Operation I. EXPECTED COMPETENCIES Upon completing this Learning Element, you should be able to: 1. Identify the six cutting angles and its purpose. 2. Determine correct cutting tool to be use on a particular lathe operation. 3. Explain the operation of automatic feed and give an advantage. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 27 4. Recognize ten safety rules to follow during operation of the lathe. II. CONTENT/TECHNICAL INFORMATION Theory of Metal Cutting: Metal cutting, commonly called machining, is the removal of the unwanted metal from a work piece in the form of chips to obtain a finished product of desired size, shape, and finish. Machining undoubtedly is the most important of the basic manufacturing processes. Most theories have ignored the plastic deformation properties of the work material and/or have not properly characterized the interactions at the contact zone between the tool and the chip. The problem is further complicated by tool geometry variations, the wide variety of tool materials used in the process, temperature or heat problems, and the great variation in operating conditions of the machines performing this process. There are seven basic chip formation processes: shaping (planning), turning (boring), milling, drilling, sawing, broaching (reaming) and abrasive machining (grinding). For all metal-cutting processes, it is necessary to distinguish between speed, feed, and depth of cut. In general, speed is the primary cutting motion, which relates the velocity of the cutting tool relative to the work piece. Feed is the amount of material removed per revolution or per pass of the tool over the work piece. Cutting speed is selected depending on the cutting tool material and the work material. Machines for metal cutting are called machine tools. Metal can be separated into parts by using a tool and some source of energy to cut. The energy for cutting is supplied by the machine, and the tool utilizes one or combinations of these three tools: 1. Slicing Tool – A knife blade cuts with a slicing action. Light pressure is applied while cutting, but the velocity of movement of the cutting edge is high. 2. Wedging Tool – A cold chisel cuts with a wedging action. The pressure applied are high so additional strength is needed, and cold chisel has wide angles to provide support. 3. Scraping Tool – Materials which require a great amount of pressure or stress upon the metal to remove a chip apply all three cutting actions, pressure, direction and velocity. In a lathe: Velocity is provided by the spindle speed of the machine. Pressure by the horsepower that is applied to the spindle. Direction by the feed of the machine. These three cutting actions combined with correct tool geometry place metal to deforming forces and chip is being formed. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 28 These three cutting tools differ in the following: 1. Amount of pressure which is applied to the cutting edge. 2. The direction that the pressure is applied to the material. 3. Velocity that the cutting edge is moved in relation to the material. Energy & Power in Machining: The cutting force system in a conventional, oblique chip formation process has three components: 1. Primary cutting force acting in the direction of the cutting velocity vector. This force is generally the largest force and accounts for 99% of the power required by the process. 2. Feed force acting in the direction of the tool feed. 3. Radial of Thrust force acting perpendicular to the machined surface. Tool Geometry: Tool geometry refers to the cutting angles ground on the tip of the cutting bit which play an important part in machining. It is simplified from the three-dimensional (oblique) geometry which typifies most process, to a twodimensional (orthogonal) geometry. Basically, the chip is formed by a localized shear process which takes place over very narrow regions. The shear process is always non homogenous (discontinuous), composed of a series of shear fronts or narrow bands which produce a lamellar structure in the chips. Orthogonal machining - The cutting edge of the tool is perpendicular to the direction of motion. Oblique machining - The cutting edge and the cutting motion are not perpendicular to each other. The Six Cutting Angles: 1. Side-Relief angle - it is the angle between the ground surface (flank) and the vertical side of the tool bit before the tool is ground. This angle is called SIDE CLEARANCE and measures 10-150 as viewed on the end. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 29 2. End-Relief angle - It is the angle between the ground and surface (flank) and vertical line. This angle is also called FRONT CLEARANCE and measures 80 as viewed from the side. 3. Back rake angle - It is the angle between the pace of the tool and a time that represents the top of the unground tool bit as viewed from the side. The angle formed ranges from 80 to 100. It helps control the direction of the chip, which naturally curves into the work due to the difference in length from the outer and inner parts of the cut. It also helps counteract the pressure against the tool from the work by pulling the tool into the work. 4. Side rake angle - It is the angle between the pace of the tool and a line that represents the top of the unground tool bit as viewed from the end. The angle formed measures 140. Side Rake along with back rake controls the chip flow and partly counteracts the resistance of the work to the movement of the cutter and can be optimized to suit the particular material being cut. Brass for example requires a back and side rake of 0 degrees while aluminum uses a back rake of 35 degrees and a side rake of 15 degrees. 5. Side-cutting edge angle - It is the angle between the straight side-cutting edge and the side of the tool shank. The angle is formed at 150 as viewed from the top. 6. End-cutting edge angle - It is the angle between the cutting edge on the end of the tool and a line at a right angle to the side edge of the straight portion of the tool. It measures 200 as viewed from the top. All the other angles are for clearance in order that no part of the tool besides the actual cutting edge can touch the work. The front clearance angle is usually 8 degrees while the side clearance angle is 10-15 degrees and partly depends on the rate of feed expected. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 30 This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 31 Lathe Theories and Operation Lathe machine operations involve the turning, drilling, facing, boring threading and many more. Various tools and different orientation of the tool is used to get the desired shape. All these methods are mainly basic turning operations. 1. Centering: centering is the operation of producing conical holes in work pieces at the ends to provide bearing surface for lathe centers. 2. Turning: Turning is the process to remove excess material from the work piece basically to produce cylindrical or cone shaped objects, to the required shape and size. The most common center or engine lathe is used for preparing of various turning parts by different turning process. Straight turning produces a cylindrical surface by feeding the single point cutting tool against the rotating work parallel to the work. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 32 3. Taper turning: means to produce a conical surface by gradual reduction in diameter from a cylindrical work piece. 4. Facing: Facing is the operation of machining the ends of a work piece to produce flat surface square with the axis. This is also used to cut the work to the required length. The tool is fed perpendicular to the axis of rotation of the work piece. 5. Knurling: Knurling is the process of embossing a diamond shaped pattern on the surface of the work piece. It provides grip to the work piece. 6. Eccentric turning: If the cylindrical work piece has two separate axes of rotation, one being out of the center to the other, the work piece is eccentric and turning of different surfaces of the work piece is known as eccentric turning. 7. Thread cutting: The principle of thread cutting is to produce helical groove on a cylindrical or conical surface by feeding the tool longitudinally when the job is revolving between centers or by a chuck. 8. Chamfering: is the operation of beveling the extreme end of the work piece. 9. Grooving: is the process of reducing the diameter of a work piece over a very narrow surface. 10. Undercutting: is similar to grooving operation performed inside a hole called undercut. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 33 Figure 4. Lathe Operations ( ) MachiningProcesses Machining is one of the processes of manufacturing in which the specified shape to the work piece is imparted by removing surplus material. Conventionally this surplus material from the work piece is removed in the form of chips by interacting the work piece with an appropriate tool. This mechanicalgeneration of chips can be carried out by singlepoint or multi point tools orby abrasiveoperations thesearesummarizedonthenext page: Singlepointtooloperations Multi-pointtooloperations Abrasiveoperations This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 34 1. Turning 1.Milling 1.Grinding 2. Boring 2.Drilling 2.Lapping 3. Shaping 3.Tapping 3.Honing 4. Planing 4. Reaming 4. Super-finishing 5. Hobbing 6. Broaching 7. Sawing This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 35 III. PROGRESS CHECK A. MATCHING TEST : Match Column A with Column B. Write your answer (letters only) on the space provided. COLUMN A COLUMN B _____ 1) Enlarging an existing hole A. Shoulder turning _____ 2) Producing beveled edge B. Drilling _____ 3) Otherwise known as step turning C. Boring _____ 4) Cutting off D. Grooving _____ 5) Producing slots or necks E. Chamfering _____ 6) Turning with two ends equal F. Outside threading _____ 7) Threading a nut G. Left hand turning _____ 8) Turning towards the tailstock H. Right hand turning _____ 9) Producing hole on solid metal I. Knurling _____ 10) Threading a bolt J. Inside threading _____ 11) Turning with lathe dog as drive K. Facing _____ 12) Embossing patterns on cylindrical work L. Center drilling _____ 13) Turning towards the headstock M. Parting _____ 14) Producing a guide prior to drilling N. Plain turning _____ 15) Squaring the ends by feeding at 90 degrees O. Turning between centers P. Reaming B. Discuss the following. 1. Illustrate & state the purpose of the six cutting angles. 2. What properties should a cutting tool possess? 3. Briefly discuss the three basic types of chips 4. Name the seven basic chip formation processes. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 36 IV. REFERENCES Burghardt, H.D., Axelrod, A., & Anderson, J. (1959) McGraw-Hill, Inc. DeGarmo, E.P., Black, J.T., & Kosher, R.A. (1988). Macmillan Publishing Company, New York. Shiksha, S. (2020). Workshop Practice. Retrieved July 08, 2020 from http://ecourseonline.iasri.res.in/mod/page/view.php? This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 37 This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 38 LEARNING GUIDE Week No.: __4__ Speed, Feeds & Depth of Cut Sequence of Operations / Machining Time I. EXPECTED COMPETENCIES Upon completing this Learning Element, you will be able to: 1. Study the effect of cutting parameters such as Spindle speed, Feed rate and Depth of cut on the cutting Force in one face of the tool holder during turning operation under different combinations of cutting parameters 2. Calculate the required time for machining a given work based on a sequence of operation. 3. Establish a sequence of operation with the least machining time. II. CONTENT/TECHNICAL INFORMATION Knowledge of the speed of gears in mesh is knowledge that most machinists, auto mechanics, engineers, and inventors require at one time or another. Whenever a machinist sets a certain number of revolutions per minute of federate on a machine, he is choosing a combination of gears that will give the desired results as per material cutting speed. The meaning of cutting speeds depends upon the machine considered. On a lathe, a boring mill, or similar machines, it means the number of feet or meters on the surface of the workpiece that pass the tool in one minute. On a drill press or milling machine, the tool is rotating. Therefore, cutting speed is the speed of a point on the circumference of the drill or milling cutter in feet or meters per minute. The proper selection of a cutting speed within that range will depend upon the machinist‟s good judgment and experience. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 39 CUTTING SPEED: CS = πDN Lathe work cutting speed may be defined as the rate at which a point on the work circumference travels past the cutting tool. Cutting speed is always expressed in meters per minute (m/min) or in Feet per minute (ft/min). If a cutting speed is , the cutting tool edge breaks down rapidly, resulting in time lost to recondition the tool. With , time will be lost for the machining operation, resulting in low production rates. Based on research and testing by steel and cutting tool manufacturers, the cutting speeds for high-speed steel tools listed in table are recommended for efficient metal removal rates. These may vary slightly to suit factors such as the following: 1. Type of work material 2. Type of cutting tool material 3. Kind of cut 4. Diameter of work piece 5. Amount of feed 6. Depth of cut 7. Machine condition LATHE CUTTING SPEEDS IN METERS PER MINUTE AND FEET PER MINUTE USING A HIGH- SPEED STEEL TOOL BIT TURNING AND BORING THREADING MATERIAL ROUGH CUT FINISH CUT m/min ft/min m/min ft/min m/min ft/min MACHINE STEEL 27 90 30 100 11 35 TOOL STEEL 21 70 27 90 9 30 CAST IRON 18 60 24 80 8 25 BRONZE 27 90 30 100 8 25 ALUMINUM 61 200 93 300 18 60 If an unbroken chip is peeled from a work piece by a cutting tool for one minute, the length of that chip can be measured in feet or meters. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 40 The machinist sets the number of revolutions per minute to the nearest speed-selector chart on his machine corresponding to the value derived from the formula. Most machinists know the old rule, This is based on the effect that the size of a diameter has on revolutions per minute. A larger diameter has more feet of material on its surface or circumference to move past the tool in a given minute, so it has a slower speed. LATHE FEED: The feed of a lathe is defined as the amount the tool advances for each revolution of the work. (Unit: rev/min) Example: 1/32”-inch feed will require 32 revolutions of the work to move the carriage 1 inch: Feed rate is the amount of feed per unit of time. (Unit: in/min or mm/min), Fr = x N KINDS OF CUT: 1. Roughing cut - to remove the greater part of the excess material. 2. Finishing cut - to make the work smooth and accurate, is a finer cut. a. Very sharp tool b. Little metal removed c. Higher degree of accuracy in measurement with emphasis on refinement The rate at which the metal is cut-off depends on three things. a. Depth of cut b. Feed c. Cutting speed TWO KINDS OF FEED: 1. Sliding feed occurs when the feed is in lengthwise direction of the work piece. 2. Surfacing feed occurs when the feed is toward the center of the work piece. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 41 DEPTH OF CUT: (t = D-d / 2) The measure of the radial setting of the tool in sliding feed, and the measure of the axial setting of the tool in surfacing feed. The depth of cut is normally 5-10 times the feed. Metal Removal Rate: Volume removed divided by Cutting time Problems to check your understanding. 1. Determine the rpm(n) of the shaft. diameter(d)=25 mm, cutting speed(cs)=50 m/min. a) 636.9 b) 202.83 c) 10.615 d) none of the mentioned 3. Determine the cutting speed(cs) of the shaft mm/min. diameter(d)=25 mm, rpm(n)=50 mm/revolution a) 3.925 b) 1.25 c) 7.85 d) none of the mentioned 4. If the diameter of the work surface before machining(d1) is 100 mm and diameter of the machined surface(d2) is 50 mm. Then the depth of the cut is______ mm. a) 50 b) 25 c) 15 d) none of the mentioned 5) Find the feed from the given data (in mm/revolution). cutting speed(cs) =50 mm/minute, depth of cut(d)=100mm, metal removal rate(MRR)= 10 mm/revolution. a) 0.2 b) 0.02 c) 0.002 d) none of the mentioned This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 42 Estimating Cutting time / Machining time: (L + A) / Fr Once a definite speed and feed rate has been established for a given cut, this information can be used for both lathe and milling operations to set a cutting time or standard. If a tool feeds past work at X thousandths of an inch for each revolution, the product of the feed and rpm will give the distance covered in one minute‟s time, i.e., the. The length of the cut divided by the feed rate per minute gives the. Example A lathe tool feeds 0.008 inch per revolution. The rpm is 275. The longest cut is 5 ½ inches. How long will it take for the tool to travel this length? Fr = x N Fr = 0.008 x 275 = 2.200 inches per revolution = L / Fr = length of cut / feed rate = 5.500 / 2.200 = 2.5 minutes CALCULATION OF MACHINING TIME FOR TURNING OPERATIONS The principles of taking time have laid down by REFA (the former National Committee for time study procedures which exist now as an association for work study procedures) the amount which is given for the completion of a work order is called total time. It is the sum of set up time, machining time, indirect machining time, and delay time. SET-UP TIME – is the time needed for preparing the work piece for the execution of a certain operation and reducing it to its original state, this includes also the study of drawings, the time for adjusting the tools, etc. pout of and returning them to the storeroom. INDIRECT MACHINING TIME – is the time spend for operations and operational elements prior to, between and/or concluding basic elements. Indirect machining time occurs regularly. It includes such operational elements as picking up, positioning, removing the work piece, measuring, sharpening tools, etc. DELAY TIME – is the allowed for personal needs, overcoming fatigue, and unavoidable delays, Delay time occurs irregularly. It comprises of such conditions as walking to the lavatory, rest periods, waiting for materials, etc. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 43 MACHINING TIME – is the time during which operations are performed which contribute directly to the completion of the work order (e.g. time in which the work piece is machined, operating time of the machine, cutting). MACHINING TIME CAN BE DETERMINED BY CALCULATION: Di Di EXAMPLE: GIVEN: Dia. = 80 mm L1 = 490 mm La = 5 mm Lu = 5 mm N = 20 m/min. f = 0.5/ rev. Mt = ………L………… FR 0r f x N N = CS (1000) 3.1416 (D) L = Turning Length + La + Lu Fr = f x N L = r + La This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 44 SOLUTIONS: 20 m/min. L = 490 + 5+ 5 N= --------------- = 79 rpm = 500 (3.1416) (0.80mm) L 500 mm Tmturning = --------- ------------------------------ 12.66 min. fxN 0.5 mm/rev x 79 rev./min. FACING: L = r + La GIVEN: D = 180 mm; r = 90 mm La = 5 mm N = 20 m /min. = 0.5mm/rev Solution: L = 90 + 5 = 95 This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. TOOL BIT 45 L 95 mm Tmfacing = --------- ------------------------------ 9.5 mins. fxN 0.5 mm/rev x 20 rev./min. III.PROGRESS CHECK A. MULTIPLE CHOICE : Choose the one best and correct answer and write the letter of your choice on the blank provided before each statement. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 46 _____ 1) is the speed at which the metal is removed by the tool from the work piece. a) feed b) cutting speed c) depth of cut d) NOTA _____ 2) Which of the following represents the formula for cutting speed? cs =cutting speed, D= diameter of work, N= rpm. a) cs = (3.14*D*N) b) cs = (D*N) c) cs = (3.14*D)/N d) NOTA ____ 3) Which of the following represent the unit of cutting speed? a) meter*minute b) meter2*minute c) meter / minute d) NOTA ____ 4) _____ is the distance the tool advances for each revolution of the work. a) feed b) depth of cut c) metal removal rate d) NOTA ____ 5) Which of the following is the unit of the feed? a) mm / minute b) mm / revolution c) mm * minute d) NOTA ____ 6) The depth of cut is the_____ distance measured from the machined surface to the surface of the work piece, which is uncut. a) parallel b) perpendicular c) at 45-degree d) NOTA ____ 7) Which of the following represents the formula for the depth of cut? d1=diameter of work surface before machining and d2=diameter of the machined surface a) d1+d2 b) d1-d2 c) (d1+d2)/2 d) (d1-d2)/2 ____ 8) Which of the following represents the formula for metal removal rate? a=cutting speed, b=depth of cut, c=feed, d=revolution a) (a*b*d)/c b) (a*b)/(c*d) c) (a*b*c)/d d) NOTA ____ 9) Which of the following represents the unit for machining time? a) mm / minute b) minute / revolution c) minute d) NOTA ____ 10) Which of the following represents the formula for the machining time? s=feed of the job per revolution, l=length of the job, n=rpm. a) l / (s*n) b) (s*n) / l c) (l*s) / n d) NOTA B. Briefly discuss and solve the following. 1. Define the following and state how it is expressed? a. Lathe feed b. Depth of cut c. Cutting speed C. Problem Solving: Read, Analyze and Compute the required data. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 47 1. At what rpm should the lathe revolve to rough turn a piece of cast iron (CS = 60 SFPM) 51 mm in radius when using a HSS tool bit. 2. Determine the total machining time for a workpiece 30mm in diameter and the required length is 145 mm. Other data: Material: 38mm dia. X 149 mm Depth of cut (turning): 4mm Depth of cut (facing): 2mm Feed : 0.05 mm/rev Cutting speed : 35 SMPM 3. Fill in the Cutting Times in the table. RPM of Work Cutting Time in Feed Rate of Tool Length of Cut Minutes 300 0.0025 2 275 0.003 5 150 0.004 3¼ 800 0.002 ¾ 74 0.010 2 7/8 760 0.0015 3.625 IV. REFERENCES Burghardt, H.D., Axelrod, A., & Anderson, J. (1959) McGraw-Hill, Inc. DeGarmo, E.P., Black, J.T., & Kosher, R.A. (1988). Macmillan Publishing Company, New York. This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 48 LIST OF REFERENCES Aldabaldetrecu, P. (2002, January 2). : Technical Evolution of the Machine Tool Retrieved July 3,2020, from https://www.interempresas. net/MetalMecanicaculos/1435-Evolucion-tecnica-de-la-maquina-herramientaRe sena-historica.html Burghardt, H.D., Axelrod, A., & Anderson, J. (1959) McGraw-Hill, Inc. DeGarmo, E.P., Black, J.T., & Kosher, R.A. (1988). Macmillan Publishing Company, New York. Shiksha, S. (2020). Workshop Practice. Retrieved July 08, 2020 from http://ecourseonline.iasri.res.in/mod/page/view.php? Operation Instruction Manual as provided by the equipment supplier. Alberta Enterprise & Advanced Education (2013). Millwright: Lathe Components & Accessories (Machining) Retrieved July 9, 2020 from https://student.eastcoast.ac.uk/pluginfile.php/40430/mod_resource/content/1 /L athe%20Components%20and%20Accessories.pdf Learning Element, Machine Shop. Training Technology Department, National Institute for Skills and Development. National Manpower and Youth Council. Philippines This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 49 ABOUT THE AUTHOR/S ELEAZAR F. TANTIADO Magsaysay Avenue, Barangay 9 Isabela, Negros Occidental, 6128 [email protected] 09164942361 EDUCATIONAL BACKGROUND Doctor of Technology, 2015 up to present – Technological University of the Philippines Master of Technology, June 2013 – Technological University of the Philippines BS Mechanical Engineering, 1999 – Technological University of the Philippines Visayas Diploma in Mechanical Eng‟g Technology, 1997 - Technological University of the Philippines Visayas DESIGNATIONS Department in Charge MET Department June 2019 to present Head (University Curriculum and Instructional Materials Development) Oct 2017 to present BAC Member TUP Visayas 2017 to present Senior High School Administrator SHS Department June 2016 to Apr 2018 Program Coordinator College of Engineering Technology Jan 2016 to Sept 2017 Internal Auditor TUP V Internal Audit Team 2016 to present Department in Charge MET Department Sept 2014 – Jan 2016 RESEARCH PRESENTATION / CONFERENCE May 26-29, 2015. National Engineering Research Symposium: Development of Automated Steam Turbine Water Cooling System, MMSU-Batac, Ilocos Norte May 16-18, 2018. International-Workshop on “Action Research as a Qualitative Research Design, Puerto Princesa, Palawan, Philippines (Johanna Research and Training Center) TEACHING EXPERIENCE June 2010 to present FacultyCOET - MET Department TUP Visayas November 2009 – March 2010 FacultyCOE – ME Department CSA-Bacolod NON-ACADEMIC DISTINCTIONS / RECOGNITION: NC II - Driving August 20, 2012 - August 20, 2017 NCII - Machining March 28, 2016 - March 27, 2021 This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 50 NC I – Shielded Metal Arc Welding (SMAW) August 24, 2017 – August 23, 2022 MEMBERSHIPS / AFFILIATIONS Philippine Society of Mechanical Engineers Board of Director 2015 – 2018 ELMER ANDREW B. LLORCA Block 3, Lot 8 Menlo Heights Phase 3 Barangay Zone 10, Talisay City, Negros Occidental, 6115 [email protected] 09157537605 Master of Technology, June 2015 up to present – Technological University of the Philippines BS Engineering Technology, 1994 – Technological University of the Philippines Visayas BS Engineering Technology, 1994 – Technological University of the Philippines Visayas Mechanical Engineering Technology, 1991 - Technological University of the Philippines Visayas Designations Department in Charge MET Department Sept 2018 – Jun 2019 Laboratory in charge MET Department Sept 2013 up to present TEACHING EXPERIENCE June 2017 to present FacultyCOET - MET Department TUP Visayas NON-ACADEMIC DISTINCTIONS / RECOGNITION: NC I – Shielded Metal Arc Welding (SMAW) August 24, 2017 – August 23, 2022 This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION. 51 This module is a property of Technological University of the Philippines Visayas and intended for EDUCATIONAL PURPOSES ONLY and is NOT FOR SALE NOR FOR REPRODUCTION.
