SIX WEEKS TRAINING REPORT AT OSHO FORGE LIMITED PROJECT REPORT
SUBMITTED BY AJAY KUMAR VERMA June 2013
PUNJAB TECHNICAL UNIVERSITY JALANDHAR, INDIA
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SIX WEEKS TRAINING REPORT AT OSHO FORGE LIMITED PROJECT REPORT
SUBMITTED BY AJAY KUMAR VERMA University Roll no. 1282757 Under the Supervision of Er. D.C. BHARDWAJ
CT Institute of Technology, Shahpur June 2013
PUNJAB TECHNICAL UNIVERSITY JALANDHAR, INDIA
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ACKNOWLEDGEMENT
I Express my sincere gratitude to Er. AMRITPAL SINGH , Head of Department Mechanical Engineering, CTIT, Shahpur, Jalandhar India, for his continuous encouragement and supervision throughout the course.
I would like to place on record my deep sense of gratitude to Er. HARKIRAT SINGH, Dept. of Mechanical Engineering, CTIT, Shahpur, Jalandhar India for their generous guidance, help and useful suggestions.
I also wish to extend my thanks to Mr. D.C. BHARDWAJ, for their kind help and guidance for operating the machines and providing useful information.
I am extremly thankful to Dr. MANOJ KUMAR, Director, CTIT, Shahpur, for providing me infrastructural facilities to work in. I would also like to extend my thanks to my loving parents for helping me, supporting me and encouraging me to perform this work.
I would also like to extend my thanks to my friend Mr.NEERAJ MISHRA for his complete support and help during the entire work.
AJAY KUMAR VERMA
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TABLE OF CONTENTS
1) 2) 3) 4)
INTRODUCTION INFRASTRUCTURE FORGING HEAT TREATMENT
5) MACHINE SHOP 6) HOBBING SHOP 7) CNC MACHINING 8) PRE-HEAT TREATMENT 9) INSEPECTION AND TESTING 10) MAINTENANCE
5 11 16 19 21 39 48 53 56 63
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INTRODUCTION Company Profile The Company Located in Ludhiana, Osho forging is an industrial hub of Punjab, Emson Group are the pioneers in manufacturing precision auto components for renowned OEMs of Cars, MUV, LCV, MCV, HCV and tractors. A modest beginning in 1970 and over 3 decades of expertise coupled with technical excellence enables the group to support its customer’s requirements and deliver the product with impeccable quality at a very competitive cost. With a current turnover of over 100 crores, the group has three state-of-the-art plants, Emson Gears Ltd, Osho Forge Ltd, Osho Gears and Pinion Ltd. spread over an area of 20 Acres. The facilities house dedicated lines for Producing Crown Wheel and Pinion, Transmission Gears, Axle Shafts, Synchro Assembly and Vital Engine Components with Captive Forge Shop.
Fig. Transmission gears & axle shafts
The kind of success and growth Emson Group has experienced over the past three decades can only be attributed to its Engineering excellence, its dedicated employees, innovative technology, impeccable quality and its commendable customer services.
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The group has a work force of over 1000 nos. consisting of professionals, engineers, technocrats and highly skilled workmen. To keep them abreast with the changing trends and Technologies, the company imparts training at periodical intervals. The company is expanding its horizons by venturing into Auto Subassemblies including Complete Axle Shaft Assembly, Transmission Gear Boxes and Syncro Assembly. The group is poised to achieve a turnover of over 200 Crores by 2008-09.
Mission To provide superior value for money to customers through quality and cost effective products by improving level of efficiency and productivity. To achieve sustainable growth by continuously seaking new business opportunities/challenges employing contemporary technologies and maintaining a high performances work culture.
Vision To be a premier conglomerate in the business of Transmission gear boxes, Rear Axle Shaft Assy. and related products.
Core Values Honesty & Integrity
Customer Delight
Innovation & Creativity
Transparency
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PRODUCTS Transmission Gears Emson manufactures 3 million gears annually for renowned OEM's in India and overseas customers. The company’s capacity in terms of size ranges from 30mm to 400mm diameter to qualify into DIN-8 class of accuracy for applications in Cars, Trucks and Tractors.
Straight Bevel Gears Emson has the expertise to produce differential gears for various applications such as car's, LTV's, SUV's, LCV's, Heavy Trucks and tractors. The production is carried out on high precision automatic straight bevel gear generators.
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Crown Wheel and Pinion Sets The crown wheel & pinion are the stressprone parts of a vehicle. These parts are made durable and efficient through the latest technologies at Emson using the Gleason machining line to produce 1,80,000 sets per annum. The company offers Crown wheel & Pinion sets ranging from 125mm to 500mm in diameter and from 4 to 12 module.
Rear Axle Shafts Rear Axle Shaft are manufactured using high grade carbon steels as raw material. These undergo strict physical endurance tests and metallurgical examination before being put to use. The Rear Axle shafts have the sturdiness and the durability to function efficiently. The present capacity is 150,000 units annually and is being enhanced by another 200,000 units annually.
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Synchro Assemblies Emson Gears has the expertise to manufacture high quality Synchro Assemblies with unmatched features. The synchro assemblies are directly integrated with the integral gears through a precision anti-backlash instrument to obtain high accuracy of positioning data.
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CLIENTS
Tata Motors Limited
Ashok Leyland Limited
Eicher Motors Limited Mahindra & Mahindra Limited
Swaraj Mazda Limited Iran Khodro Ind. Group
Baxy Continental Engines Limited
International Tractors Limited
TVS Motor Co. Limited
Panjab Tractors Limited
Greaves cotton Ltd.
Tafe Motors & Tractors Limited
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INFRASTRUCTURE Emson Group boasts of a state-of-the-art infrastructure with world-class facilities. All its manufacturing plants possess sophisticated and hi-tech machines which helps in the production of fully finished Transmission and Differential components with finest quality.
Forging Emson has most modern forging plant
equippe with Drop Forging Hammers and
Horizontal Forging Machines, Upsetters and Presses etc.
Isothermal Annealing The Isothermal Annealing Furnaces at Emson has a capacity of 1000 kg per hour.
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Blank Turning With a plethora of about 100 CNC turning Centers, Lathes, CNC Twin Spindle Chuckers of world renowned makes such as MORISIEKI, MAZAK, CINCINNATI, HYUNDAI, COLCHESTER, HMT, FRONTOR WIESSER and SUGA etc with diameter range from 30 mm to 600 mm.
Broaching Emson has vertical broaching machines with capacity ranging from 6 Tons to 40 Tons from maker like Frost, American Broach, Varinelli and HMT etc.
Spline Rolling The company has modern ROTO FLO spline rolling machines to make cold-formed splines on gear shafts as per the design specifications.
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Transmission Gears Presently the Transmission Gears facility at Emson comprises of more than 150 conventional and CNC Hobbing, Shaping and Shaving machines of world renowned makes such as GLEASON, PFAUTER, HURTH, LIEBHERR, LORENZ, HMT, WMW and RED RING etc to churn out 3 million units annually.
Emson’s capacity in terms of size ranges from 30mm to 400mm diameter to qualify into DIN -8 class of accuracy for applications in Cars, Trucks and Tractors. On the anvil are plans for adding capacity for another 200,000 gears a month to keep pace with rapid growth of automotive industry.
Differential Gears Emson has capacity to produce Bevel gears of various disciplines and applications on bevel generators such as Gleason-104 and WMW Machines. A battery of 10 machines is deployed to produce 300,000 bevel gears per annum for differential assemblies of cars, trucks, tractors and Earth Moving Machines.
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Crown Wheel and Pinion Sets With dedicated Gleason Machining Line and state-of-the-art Heat Treatment Facility, the group is capable of providing 1,80,000 sets per annum for various applications such as Cars, Trucks, Buses, Tractors, Delivery Vehicles. The facilities can churn out Crown wheel & Pinion sets ranging from 125 mm to 500mm in diameter and from 4 to 12 module. The Crown wheel & Pinion sets are duly lapped and tested for noise levels, performance parameters, fitment and durability.
Rear Axle Presently, the group has in house forging equipments and machining facilities to produce 1,50,000 Axle Shafts annually for OEM and export requirements. A dedicated machining line with battery of induction hardening machines are installed to produce Axle Shafts for Cars, Trucks and Tractors. Capacity expansion for another 200,000 Axle shafts is under installation and production is likely to commence from Oct, 2007.
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Synchronizer Hubs and Sleeves EMSON has world renowned ZF Make Internal Gear Rolling Machine capable of processing Synchro Hubs,Synchro Sleeves, Clutch bodies for various Automotive Gear Boxes
Heat Treatment The Heat Treatment Facility at Emson is well equipped with modern state of the art Sealed Quenched Furnaces, Carburizing Furnace, Induction Hardening machines, Rotary Hearth Furnaces and Isothermal annealing plant etc.The heat treatment is further supported by wellequipped laboratories comprising of Automatic Micro Hardness Tester, Microscopes and Jominy hardenability testing equipments.
Grinding At Emson Grinding Operations are carried on various CNC and Conventional grinding machines of various make to achieve optimum level of accuracy as per the customers’ specifications.
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FORGING SHOP
Forging involves heating of a metal stock to a desired temperature; enable it to acquire sufficient plasticity followed by the operations like hammering, bending & piecering etc. to give it the desired shape. The forging process is very important and has indispensable position among the various manufacturing processes generally adopted in the workshops due to some reasons i.e. it refines the structures of metal, it renders the metal stronger by setting the direction of the grains & it effects considerable saving in time the labour and material as compared to the production of same by cutting from a solid stock and then shaping it.
Fig. Drop forging
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Working Procedure in Forging Shop
Material cutting: - This is the first step which is involved in forging. After the material is received & inspected it is sent for the material cutting. In material cutting operation the material is cut in accordance with the required dimensions. The material cutting is done on band saw machines which are fully automatic in operation. After the material cutting is done the material is sent into the forging shop.
Heating: - This is the second step which is involved. In this step the material is heated to the forging temperature in the furnace. The forging temperature is 1250-1300 degrees. The furnaces which are used are oil-fired furnaces & they can be either pusher type or batch type. After the material is heated it is sent to the forging machines. The process of heating the stock can be divided into two stages:-
First stage (Preheating zone): - In this stage the temperature to which the stock is heated is 500700 degrees. Second stage(Full heating zone): -In this stage the temperature is 1260-1300 degrees.
Forging: - In this step the material is forged on either a drop hammer or a forging press or on the up-setter. The type of the machine which is to be used depends upon the shape & size of the component to be forged.
Trimming: - In this operation the excess & unwanted material is removed from the forged component. After forging operation is done then the forged component is passed to the trimming press for the material removal.
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Various hammers present in shop with specifications 1. Friction Drop Hammers : 4 1 Ton- 2 no 2 Ton- 2 no
2. Horizontal Upsetter: 1 600 Ton
3. Mechanical Presses: 4 400 Ton, 500 Ton 630 Ton, 1300 Ton
Temperature Measurement Instruments Used in Forging Shop 1. Thermocouple 2. Optical Pyrometer
The thermocouples are located at suitable heating zones inside the furnace & they measure the temperature of the heating zone & this temperature is represented on the digital temperature indicator to the operator.
Furnace oil used in forging shop The furnance oil which is used in the furnances is the residual furnace oil. Fuel consumption in the furnances is 100 liters.
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HEAT TREATMENT NORMALIZING Normalizing operation is done so as:a) To improve the machinability. b) To modify the refine the grain structure. c) To obtain relatively good ductility without reducing the hardness and strength.
Generally , the normalizing temperature is 920-930 `c and is done in batch furnance. Then the component is placed at that temperatute Upto 1 hour or as per reuirement and then it is air cooled till the temperature Reaches the room temperature.
ANNEALING Metallic materials consist of a microstructure of small crystals called ―grains‖ or crysatallites. The nature of the grains (i.e. grain size and composition) determines the overall mechanical behaviour of the metal. Heat treatment provides an efficient way to manipulate the properties of the metal by controlling rate of diffusion and the rate of cooling with in the microstructure. Annealing is a technique used to recover cold work and relax stresses within the metal. Annealing typically results in a soft ductile metal. When an annealed part ia allowed to cool in the furnace, it is called a ―full anneal‖ heat treatment. When an annealed part is allowed to cool in the furnace and allowed to cool in air. It is called a ―normalizing‖ heat treatment. During annealing, small grains recrystallize to form larger grains.
Isothermal annealing In this process the components is heated as per desired temperature 640C hold for 30 minutes and cooled fast below hypoeutecoid steel temperature for sufficient period for completion of transformation and then cooled to room temperature at air. It shows following advantage over conventional annealing
Improved machinability
Improved surface finish
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Shot Blasting After the pre-heat treatment processes done on the products, the next opertion is Short Blasting. Short blasting is the most widely used process of the cleaning, stripping and improving the metal surface. The grade or size of shot will be determine the ultimate finish achieved on the surface of metal. It is the process done after normalizing, in this srcnal colour of material is obtained. Shot blasting is done in the machine which throws the huge amount of shots at very high velocity, which stricks the component and thus blasting process is complete. The time required for complete that operation is 30minutes and actual shot grade is S-660.
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MACHINE SHOP
After Forging and Pre Heat Treatment the next process in making a part is machining, where the exact dimensions of the part is obtained. Machining is any of various processes in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process Much of modern day machining is carried out Computer numerical control (CNC), in which computers are used to control the movement and operation of the mills, lathes, and other cutting machines.
Types of Machining operation There are many kinds of machining operations, each of which is capable of generating a certain part geometry and surface texture.
Turning:- In turning a cutting tool with a single cutting edge is used to remove material from a rotating workpiece to generate a cylindrical shape. The speed motion is provided by rotating the workpiece, and the feed motion is achieved by moving the cutting tool slowly in a direction parallel to the axis of rotation of the workpiece.
Drilling:- Drilling is used to create a round hole. It is accomplished by a rotating tool that typically has two or four helical cutting edges. The tool is fed in a direction parallel to its axis of rotation into the workpiece to form the round hole.
Boring:- In boring, a tool with a single bent pointed tip is advanced into a roughly made hole in a spinning workpiece to slightly enlarge the hole and improve its accuracy. It is a fine finishing operation used in the final stages of product manufacture.
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Milling:- In milling a rotating tool with multiple cutting edges is moved slowly relative to the material to generate a plane or straight surface. The direction of the feed motion is perpendicular to the tool's axis of rotation. The speed motion is provided by the rotating milling cutter.
Broaching :- Broaching is a machinig process that uses a toothed tool, called a broach, to remove material. There are two main types of broaching: linear and rotary. In both processes the cut is performed in one pass of the broach, which makes it very efficient.
Lathe Machines Used in Industry A lathe machine is used for the shaping and machining of various work pieces.
Explanation of the standard components of most lathes: Provides a heavy Bed:Usually made of cast iron.
rigid frame
On which all
the main components are mounted. Ways Inner and outer guide rails that are precision machined parallel to assure accuracy of
movement.
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Headstock: mounted in a fixed position on the inner ways, usually at the left end. Using a
chuck, it rotates the work. Gearbox: inside the headstock, providing multiple speeds with a geometric ratio by moving
levers. Spindle: Hole through the headstock to which bar stock can be fed, which allows shafts that
are up to 2 times the length between lathe centers to be worked on one end at a time. Chuck: 3-jaw (self centering) or 4-jaw (independent) to clamp part being machined. Chuck: allows the mounting of difficult workpieces that are not round, square or triangular. Tailstock: Fits on the inner ways of the bed and can slide towards any position the headstock
to fit the length of the work piece. An optional taper turning attachment would be mounted to it. Tailstock Quill: Has a Morse taper to hold a lathe center, drill bit or other tool. Carriage: Moves on the outer ways. Used for mounting and moving most the cutting tools. Cross Slide: Mounted on the traverse slide of the carriage, and uses a handwheel to feed tools
into the workpiece. Tool Post: To mount tool holders in which the cutting bits are clamped. Compound Rest: Mounted to the cross slide, it pivots around the tool post. Apron: Attached to the front of the carriage, it has the mechanism and controls for moving the carriage and cross slide. Feed Rod: Has a keyway, with two reversing pinion gears, either of which can be meshed with
the mating bevel gear to forward or reverse the carriage using a clutch. LeadScrew: For cutting threads. Split Nut: When closed around the lead screw, the carriage is driven along by direct drive
without using a clutch. Quick Change Gearbox: Controls the movement of the carriage using levers. Steady Rest: Clamped to the lathe ways, it uses adjustable fingers to contact the workpiece and
align it. Can be used in place of tailstock or in the middle to support long or unstable parts being machined. Follow Rest:Bolted to the lathe carriage, it uses adjustable fingers to bear against the
workpiece opposite the cutting tool to prevent deflection.
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TYPES OF LATHES There are three general types of lathe machines:-
Engine lathes. These are probably the most popular among the lathe machines. In fact, no machine shop is seen without this type of lathe. The good thing about engine lathes is that it can be used in various materials, aside from metal. Moreover, the set-up of these machines is so simple that they are easier to use. Its main components include the bed, headstock, and tailstock. These engine lathes can be adjusted to variable speeds for the accommodation of a wide scope of work. In addition, these lathes come in various sizes.
Turret Lathes. These types of lathes are used for machining single workpieces sequentially. This means that several operations are needed to be performed on a single work piece. With the turret lathes, sequential operations can be done on the work piece, eliminating errors in work alignment. With this set-up, machining is done more efficiently. Correspondingly, time is saved because there is no need to remove and transfer the work piece to another machine anymore.
Special Purpose Lathes. As the name implies, these lathes are used for special purposes such as heavy-duty production of identical parts. In addition, these lathes also perform specific functions that cannot be performed by the standard lathes. Some examples of special purpose lathes include the bench-type jewelers’ lathes, automatic lathes, crankshaft lathes, duplicating lathes, multispindle lathes, brakedrum lathes, and production lathes among others
Various types of operations perfoemed on lathes
Facing Facing is the process of removing metal from the end of a workpiece to produce a flat surface. Most often, the workpiece is cylindrical, but using a 3or 4 jaw chuk you can face rectangular or odd-shaped work to form cubes and other non-cylindrical shapes.When a lathe cutting tool removes metal it applies considerable tangential (i.e. lateral or sideways) force to the workpiece.
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Turning Turning is a machining process in which a cutting tool typically a non-rotary tool bit describes a helical toolpath by moving more or less linearly while the workpiece rotates. The tool's axes of movement may be literally a straight line, or they may be along some set of curves or angles, but they are essentially line. Usually the term "turning" is reserved for the generation of external surfaces by this cutting action.
Chamfer Chamfer is a beveled edge connecting two surfaces. If the surfaces are at right angles, the chamfer will typically be symmetrical at 45 degrees. "Chamfer" is a term commonly used in mechanical and manufacturing engineering Special tools such as chamfer mills and chamfer planes are available.
Boring A boring is the process of enlarging a hole that has already been drilled or cast, by means of a single point cutting tool . Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to turning which cuts external diameters
Reaming Reamer is a type of rotary cutting tool used in operation . Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precision reamers which are used for more basic enlargement of holes or for removing burrsThe process of enlarging the hole is called Reaming.
DRILLING Drilling is a cutting process that uses a drill bit to cut or enlarge a hole of circular crosssection in solid materials. The drill bit is a rotary cutting tool, often multipoint. The bit is pressed against the workpiece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the workpiece, cutting off chips from the hole as it is drilled.
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Types of Drilling Machines There are many different types or configurations of drilling machines, but most drilling machines will fall .into four broad categories: upright sensitive, upright, radial, and special purpose.
Upright Sensitive Drill Press The upright sensitive drill press is a light-duty type of drilling machine that normally incorporates a belt drive spindle head. This machine is generally used for moderate-to-light duty work. The upright sensitive drill press gets its name due to the fact that the machine can only be hand fed. Hand feeding the tool into the workpiece allows the operator to "feel" the cutting action of the tool. The sensitive drill press is manufactured in a floor style or a bench style.
Fig. Upright sensitive drill press
Upright Drill Press The upright drill press is a heavy duty type of drilling machine normally incorporating a geared drive spindle head. This type of drilling machine is used on large hole-producing operations that typically involve larger or heavier parts. The upright drill press allows the operator to hand feed or power feed the tool into the workpiece. The power feed mechanism automatically advances the tool into the workpiece. Some types of upright drill presses are also manufactured with automatic table-raising mechanisms. 26 | Page
Fig. Upright drill press
Radial Arm Drill Press The radial arm drill press is the hole producing work horse of the machine shop. The press is commonly refered to as a radial drill press. The radial arm drill press allows the operator to position the spindle directly over the workpiece rather than move the workpiece to the tool. The design of the radial drill press gives it a great deal of versatility, especially on parts too large to position easily. Radial drills offer power feed on the spindle, as well as an automatic mechanism to raise or lower the radial arm. The wheel head, which is located on the radial arm, can also be traversed along the arm, giving the machine added ease of use as well as versatility. Radial arm drill presses can be equipped with a trunion table or tilting table . This gives the operator the ability to drill intersecting or angular holes in one setup.
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Fig. Radial arm drill press
Special purpose drill machines There are a number of types of special purpose drilling machines. The purposes of these types of drilling machines vary. Special purpose drilling machines include machines capable of drilling 20 holes at once or drilling holes as small as 0.01 of an inch.
Gang Drill Press The gang style drilling machine (Figure 4) or gang drill press has several work heads positioned over a single table. This type of drill press is used when successive operations are to be done. For instance, the first head may be used to spot drill. The second head may be used to tap drill. The third head may be used, along with a tapping head, to tap the hole. The fourth head may be used to chamfer.
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Fig. Gang drill press
Milling Milling is the machining process of using rotary cutters to remove material from a workpiece advancing (or feeding) in a direction at an angle with the axis of the tool. It covers a wide variety of different operations and machines, on scales from small individual parts to large, heavy-duty gang milling operations. It is one of the most commonly used processes in industry and machine shops today for machining parts to precise sizes and shapes.
Types of Miliing Machines Milling machines are a very versatile machine tool. Milling machines are capable of machining one or two pieces as well as large volume production runs. The milling machine can produce a variety of surfaces by using a circular cutter with multiple teeth that progressively produce chips as the cutter rotates as shown in figure.
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Fig. Carbide face mill used on a vertical milling machine.
The advantage of having a circular milling cutter with multiple teeth has led to the design of a large variety of milling machine types. These different milling machine types can be classified as Knee and Column, Fixed Bed, Bridge Type, and Special. All of these classifications can have either a vertical or horizontal spindle configuration. Further classifications of milling machines are made on the basis of the type of computer numerical control the machine uses.
Knee and column type milling machine The knee and column type milling machine is a very versatile machine. This type of milling machine is found primarily in job shops and tool and die shops. The most distinguishing characteristic of this type of machine is the knee and column configuration .
This type of milling machine is unique in that the table can be be moved in all three directions. The table can be moved longitudinally in the X-axis as well as in and out on the Y-axis. Since the table rides on top of the knee, the table can be moved up and down on the Z-axis. There are several different types of knee and column type milling machines, but they all have the same characteristic. The knee slides up and down on the column face.
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Fig. Horizontal knee and column type milling machine.
Fig. Vertical knee and column type milling machine
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Universal knee and column milling machine The universal knee and column milling is very similar to the plain knee and column milling machine. The largest difference being the swiveling table housing. The swiveling table housing allows the table to be swiveled at an angle to the axis of the spindle .
Fig. Universal horizontal knee and olumn milling machine machine with the swivel table.
Vertical knee and column type milling machine A vertical type knee and column milling machine has the spindle located vertically, parallel to the face of the column, and perpendicular to the top of the table. The ram style knee and column type milling machine is a light duty milling machine. This type of machine is well suited for a variety of tool room work as well as other light duty operations. The head is mounted on a ram that can be swiveled or brought forward. This allows the head to be brought into an operating position over most of the table.
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Fig. Ram style knee and column type vertical milling machine.
Fixed bed type milling machines The most distinguishing aspect of the fixed bed type milling machine is the absence of the knee. The fixed bed construction of this style of milling machine minimizes deflection and allows very heavy cuts to be taken. Fixed bed style milling machines can be used for general purpose work although many people look upon them as high production machines. The table can move in a longitudinal and a transverse direction. The vertical position of the spindle, with respect to the work table, is obtained by moving the head up and down along the column of the machine.
Fig. Fixed Bed Horizontal Milling Machine
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Broaching Broaching is a machining process that pushes or pulls a broach over or through the surface being machined. Its high-production, metal-removal process is sometimes required to make one-of-a-kind parts.. Early broaching applications were cutting keyways in pulleys and gears. Today, almost every conceivable type of form and material can be broached. It represents a machining operation that, while known for many years, is still in its infancy. New uses for broaching are being devised every day. Broaching is similar to planing, turning, milling, and other metal cutting operations in that each tooth removes a small amount of material.
Fig. Cutting action of a broaching tool.
The broaching tool has a series of teeth so arranged that they cut metal when the broach is given a linear movement as indicated in figure 1. The broach cuts away the material since its teeth are progressively increasing in height.
Fig. Typical push keyway broaching tools and a shim
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Properly used, broaching can greatly increase productivity, hold tight tolerance,and produce precision finishes. Tooling is the heart of broaching. The broach tool's construction is unique for it combines rough, semi-finish, and finish teeth in one tool.
Fig. Parts of a broaching tool.
There are two types of broaching procedures: internal broaching and external broaching. For exterior broaching, the broach tool may be pulled or pushed across a workpiece surface, or the surface may move across the tool. Internal broaching requires a starting hole or opening in the workpiece so the tool can be inserted. The tool, or workpiece, is then pushed or pulled to force the tool through the starter hole. Almost any irregular cross-section can be broached as long as all surfaces of the section remain parallel to the direction of broach travel (Figure 4). Helical cuts can also be produced by twisting the broach tool as it passes the workpiece surface.
Fig. Different types of broaches.
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In conclusion, it may be said that the broach tool and the broaching process are versatile and important and that anyone who works in the field of metals, woods, or plastics should be familiar with them.
Grinding Grinding is an abrasive machining process that uses a grinding as the cutting tool. A wide variety of machines are used for grinding: Grinding is used to finish workpieces that must show high surface quality and high accuracy of shape and dimension A Grinding machine, often shortened to grinder , is a machine tool used for grinding which is a type of machining using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear deformation. . As the accuracy in dimensions in grinding is on the order of 0.000025 mm, in most applications it tends to be a finishing operation and removes comparatively little metal, about 0.25 to 0.50 mm depth. However, there are some roughing applications in which grinding removes high volumes of metal quite rapidly. Thus, grinding is a diverse field.
Grinding machine main parts The grinding machine consists of a bed with a fixture to guide and hold the work piece, and a power-driven grinding wheel spinning at the required speed. The speed is determined by the wheel’s diameter and manufacturer’s rating. The user can control the grinding head to travel across a fixed work piece, or the work piece can be moved while the grind head stays in a fixed position. Fine control of the grinding head or tables position is possible using a vernier calibrated hand wheel, or using the features of numerical controls. Grinding machines remove material from the work piece by abrasion, which can generate substantial amounts of heat. To cool the work piece so that it does not overheat and go outside its tolerance grinding machines incorporate a coolant. The coolant also benefits the machinist as the heat generated may cause burns. In high-precision grinding machines (most cylindrical and surface grinders), the final grinding stages are usually set up so that they remove about
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200 nm (less than 1/10000 in) per pass - this generates so little heat that even with no coolant, the temperature rise is negligible.
Types of Grinder
Suface Grinder
Fig. Sufrace grinder
Cyliderical grinder
Fig. Cylinderical grinder These machines include the :
Belt grinder:- which is usually used as a machining method to process metals and other
materials, with the aid of coated abrasives. Sanding is the machining of wood; grinding is the common name for machining metals. Belt grinding is a versatile process suitable for all kind of applications like finishing, deburring, and Stock removal.
Bench grinder:- which usually has two wheels of different grain sizes for roughing and
finishing operations and is secured to a workbench or floor stand. Its uses include shaping tool bits or various tools that need to be made or repaired. Bench grinders are manually operated.
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Cylindrical grinder:-
which
includes
both the
types
that
use
centers and
the centerless types. A cylindrical grinder may have multiple grinding wheels. The workpiece is rotated and fed past the wheels to form a cylinder.It is used to make precision rods, tubes, bearing races, bushings, and many other parts.
Surface grinder:- which includes the wash grinder. A surface grinder has a "head" which
is lowered, and the workpiece is moved back and forth past the grinding wheel on a table that has a permanent magnet for use with magnetic stock.
Tool and cutter grinder :- These usually can perform the minor function of the drill
bit grinder, or other specialist tool room grinding operations.
Gear grinder:-
which is usually employed as the final machining process when
manufacturing a high-precision gear. The primary function of these machines is to remove the remaining few thousandths of an inch of material left by other manufacturing methods .
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HOBBING SHOP
Hobbing is a machining process for making gears, splines and sprockets on a Hobbing 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 gears, helical gears , involute and more gears are cut by hobbing than any other process since it is relatively quick and inexpensive.
GEAR CUTTING Gear is one of the important machine tool elements which is an integral and inevitable part of power transmission system. A gear is a round blank having teeth along its periphery. Gears are used to transfer power or torque from prime mover to the place where it is to be used. Along with the transmission of power gears also transfer the accurate velocity ratio between two shafts. Velocity ratio is defined as the ratio of rpm of the driven shaft to the rpm of driver shaft. Power is normally transferred with the help of pair of gears in mesh together, each of these two are mount on driven shaft and driver shaft. RPM of driven shaft or driven gear Velocity Ratio = RPM of gear driver shaft or driver The gear mounted on the driver shaft is called driver gear and an other gear mounted on the driven shaft is called driven gear. Driver gear and driven gear both constitute a pair of mating gears, these gears are identical with reference to all parameters except their diameters and number of teeth.
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GEAR TERMINOLOGY The gear terminology is explained below with reference to a spur gear which is a particular type of a gear. The detail of gear terminology are shown below:-
Fig. Gear terminology
Addendum Circle
It is an imaginary circle which passes through top of all gear teeth and represents maximum diameter of a gear. This maximum diameter is equal to gear blank diameter. Addendum
Addendum of a gear is the radial distance between addendum circle and pitch circle of the gear. Pitch Circle
This is an imaginary circle along which thickness of a gear tooth becomes equal to spacing between them.
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Deddndum
It is the radial distance between pitch circle and root circle of a gear. Root Circle
Root circle is an imaginary circle which is supposes to pass through root of all gear teeth. Tooth Clearance
This is the distance between the top of a tooth of one gear and the bottom of the corresponding tooth of other mating gear is known as clearance or tooth clearance. Pressure Angle
The angle made by the line of action with the common tangent to the pitch circle is called pressure angle. Face
It is the portion of the tooth lying between top of the tooth and pitch circle. Flank
This is portion of the gear tooth between its pitch circle and root circle. Thickness of a Gear Tooth
It is also called chorodal thickness of gear tooth. It is width of two gear tooth measured along the pitch circle. At the pitch circle width of gear tooth becomes equal to the width of spacing between two consecutive gear teeth. Backlash It is difference between actual tooth thickness and the width of space at which it meshes with other gear. Circular Pitch
It is the distance between corresponding points of adjacent teeth measured along the pitch circle. Diametral Pitch
It is number of teeth of a gear per unit of pitch circle diameter. Module It is reciprocal of diameteral pitch. It is linear distance in mm that each tooth of the
gear would occupy if the gear teeth were spaced along the pitch diameter.
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Gears Shaping Gear shaping is one of the gear generating methods. In this process gear tooth are accurately sized and shaped by cutting them by a multipoint cutting tool. Various gear shaping processes are listed and then described below:(a) Gear cutting by gear shaper (b) Rack planning process (c) Hobbing process
Gear Cutting by Gear Shaper This process uses a pinion shaped cutter carrying clearance on the tooth face and sides and a hole at its centre for mounting it on a stub arbor or spindle of the machine. The cutter is mounted by keeping its axis in vertical position. It is also made reciprocating along the vertical axis up and down with adjustable. predecide amplitude. The cutter and the gear blank both are set to rotate at very low rpm about their respective axis. The relative rpm of both (cutter and blank) can be fixed to any of the available value with the help of a gear train. This way all the cutting teeth of cutter come is action one-by-one giving sufficient time for their cooling and incorporating a longer tool life. The specific advantages of the process over other processes, its product cycle time is very low and negligible dimensional variability from one unit to other in case of mass production. The principle of gear cutting by this process as explained above is depicted in the figure.
Fig. Gear shaper
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Main advantages of gear shaping process are discussed below (a) Shorter product cycle time and suitable for making medium and large sized gears in mass production. (b) Different types of gears can be made except worm and worm wheels. (c) Close tolerance in gear cutting can be maintained. (d) Accuracy and repeatability of gear tooth profile can be maintained comfortably. (e) For same value of gear tooth module a single type of cutter can be used irrespective of number of teeth in the gear.
Limitations (a) It cannot be used to make worm and work wheel which is a particular type of gear. (b) There is no cutting in the return stroke of the gear cutter, so there is a need to make return stroke faster than the cutting stroke. (c) In case of cutting of helical gears, a specially designed guide containing a particular helix and helix angle, corresponding to the teeth to be made, is always needed on urgent basis.
Gear Shaping by Rack Shaped Cutter In this method, gear cutting is done by a rack shaped cutter called rack type cutter. The working is similar to shaping process done by gear type cutter. The process involves rotation of the gear blank as the rack type cutter reciprocates along a vertical line. Cutting is done only in the downward stroke, the upward stroke is only a return movement. The main difference of this method with the previous one is that once the full length of the rack is utilized the gear cutting of operation is stopped to bring the gear blank to its starting position so that another pass of gear cutting can be started. So this operation is intermittent for cutting larger gears having large number of teeth over their periphery. Another popular method of gear chopping is Rack Planning Process which is described below.
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Fig. Rack shaping
A few of the initial teeth of rack type cutter perform the cutting action and remaining teeth to very small removal of workpiece material, these are used to maintain dimensional accuracy of the already cut teeth and to provide them a good finishing.
Gear Hobbing Process In addition to the gear shaping process another process used for gear generation is gear hobbing. In this process, the gear blank is rolled with a rotating cutter called hob. Gear hobbing is done by using a multipoint cutting tool called gear hob. It looks like a worm gear having a number of straight flutes all around its periphery parallel to its axis. These flutes are so shaped by giving proper angles to them so that these work as cutting edges. In gear hobbing operation, the hob is rotated at a suitable rpm and simultaneously fed to the gear blank. The gear blank is alos kept as revolving. Rpm of both, gear blank and gear hob are so synchronized that for each revolution of gear bob the gear blank rotates by a distance equal to one pitch distance of the gear to be cut. Motion of both gear blank and hob are maintained continuously and steady. A gear hob is shown in Figure and the process of gear hobbing is illustrated in Figure .The hob teeth behave like screw threads, having a definite helix angle. During operation the hob is tilted to helix angle so that its cutting edges remain square with the gear blank. Gear hobbing is used for making a wide variety of gears like spur gear, helical, hearing-bone, splines and gear sprockets, etc
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Three important parameters are to be controlled in the process of gear hobbing indexing movement, feed rate and angle between the axis of gear blank and gear hobbing tool (gear hob). A schematic diagram of the setup of a gear hobbing machine is illustrated in Figure The aims of hob are set at an inclination equal to the helix angle of the hob with the vertical axis of the blank. If a helical gear is to be cut, the hob axis is set at an inclination equal to the sum of the helix angle of the hob and the helix angle of the helical gear. Proper gear arrangement is used to maintain rpm ratio of gear blank and hob.
Fig. Gear hobbing
The operation of gear hobbing involves feeding the revolving hob till it reaches to the required depth of the gear tooth. Simultaneously it is fed in a direction parallel to the axis of rotation. The process of gear hobbing is classified into different types according to the directions of feeding the hob for gear cutting. The classification is described as given below.
Hobbing with Axial Feed In this process the gear hob is fed against the gear blank along the face of the blank and parallel to its axis. This is used to make spur and helical gears.
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Hobbing with Radial Feed In this method the hob and gear blanks are set with their axis normal to each other. The rotating hob is fed against the gear blank in radial direction or perpendicular to the axis of gear blank. This method is used to make the worm wheels.
Hobbing with Tangential Feed This is also used for cutting teeth on worm wheel. In this case, the hob is held with its axis horizontal but at right angle to the axis of the blank. The hob is set at full depth of the tooth and then fed forward axially. The hob is fed tangential to the face of gear blank.
Hob 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.
Fig. Hob cutter
Advantages and Limitations of Gear Hobbing Process (a) Gear hobbing is a fast and continuous process so it is realized as economical process as compared to other gear generation processes. (b) Lower production cycle time, i.e. faster production rate. (c) The process has a larger variability’s in the following of sense as compared to other gear machining processes. (i) Capable to make wide variety of gears like spur gear, helical gears, worms, splines, sprockets, etc
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(ii) Process of required indexing (named so) is quite simplified and capable to make any number of teeth with consistent accuracy of module. (iii) A special type of gear named harringbon gear cam be generated by gear hobbing exclusively. (iv) Wide variety of batch size (small to large volume) can be accommodated by this process. (d) Several gear blanks, mounted on the same arbor, can be processed simultaneously. (e) Hob is multipoint cutting tool having multi cutting teeth or edges at a time few number of cutting edges work so lots of time is available to dissipate the generated heat. There is no over heating and cutting tool.
Gear Shaving Gear shaving is a process of finishing of gear tooth by running it at very high rpm in mesh with a gear shaving tool. A gear shaving tool is of a type of rack or pinion having hardened teeth provided with serrations. These serrations serve as cutting edges which do a scrapping operation on the mating faces of gear to be finished. Both are gears in mesh are pressed to make proper mating contact. A shaving tool with serrated teeth is explained by illustration.
Fig. Gear shaving
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CNC MACHINING
NC & CNC Numerical control (NC) is a method of automatically operating a manufacturing machine based on a code letters, numbers and special characters.
The numerical data required to produce a part is provided to a machine in the form of program, called part program or CNC (computer numerical control).
The program is translated into the appropriate electrical signals for input to motors that run the machine.
A CNC machine is an nu.merical control machine with the added feature of an on board computer. The computer is referred to as the machine control unit (MCU)
CNC LATHES They cut metal that is often turning at fast speeds.
CNC lathes are able to make fast, precision cuts using indexable tools and drills with complicated programs.Normally, they cannot be cut on manual lathes.
They often include 12 tool holders and coolant pumps to cut down on tool wear
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Fig. Cnc lathe
CNC Turning Centers CNC Turning Centers are capable of executing many different types of lathe cutting operations simultaneously on a rotating part.
Fig. CNC Turning Centers
Advantages of CNC Machines Ease of Use a) CNC machines are easier for beginners b) Operation of several CNC machines at same time. c) Some CNC machines don’t need any operator d) Call their operator in case of the emergencies. 49 | Page
High Efficiency a) operate almost continuously 24 hours a day, 365 days a Year.
Expanding Options a) Expand the machine's capabilities with Software changes and updates.
No Prototyping a) New programmes provide elimination build a prototype, save time and money.
Precision a) Parts are identical to each other.
Reduce Waste a) Reduce waste as errors allows minimize wasted material.
Disadvantage of CNC Machines a) costs quite a lot more than conventional machinery. b) does not eliminate the need for expensive tools. c) expensive to repair.
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Vertical Machining Center(VMC) A Vertical machining center (VMC) is a machining center with its spindle in a vertical orientation. High-end VMCs are high-precision machines often used for tight-tolerance milling, such as fine die and mold work. Low-cost vertical machining centers are among the most basic CNC machine tools. A low-cost VMC is often a new machine shop’s first machine tool purchase.
Fig. Vertical Machining Center
Most CNC milling machinesare computer controlled vertical mills with the ability to move the spindle vertically along the Z-axis. This extra degree of freedom permits their use in diesinking, engraving applications, and 2.5D surfaces such as relief sculptures. When combined with the use of conical tools or a ball nose cutte, it also significantly improves milling precision without impacting
speed,
providing
a
cost-efficient
alternative
to
most
flat-surface
hand-
engraving work.
CNC machines can exist in virtually any of the forms of manual machinery, like horizontal mills. The most advanced CNC milling-machines, the multiaxis machine, add two more axes in 51 | Page
addition to the three normal axes (XYZ). Horizontal milling machines also have a C or Q axis, allowing the horizontally mounted workpiece to be rotated, essentially allowing asymmetric andeccentric turning . The fifth axis (B axis) controls the tilt of the tool itself. When all of these axes are used in conjunction with each other, extremely complicated geometries, even organic geometries such as a human head can be made with relative ease with these machines. But the skill to program such geometries is beyond that of most operators. Therefore, 5-axis milling machines are practically always programmed with CAM.
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PRE-HEAT TREATMENT
After gear and splines cutting operations in hobbing shop, the manufactured product took in Pre heat treatment or S.Q.F shop for doing further operations.there are various operations performed in that are discussed below.
Types of Process
Washing: This operation is done for removing dirt, dust and oilness
From the manufactured product and preparing for the next operation. the manufactured product took in washing machine and wash the products at temperatue 250C very accurately. Time for done this operation is 10-15 minutes.
Pre-heating: After the washing , the next operation is pre-heating. In this operation, the
manufactured products took in furnace and heating at temperature 460C. This operation is used for improving or balancing the mechanical properties of the products. the time required for complete this operation is 90 minutes.
Carburizing: The main purpose of carburizing is to obtain a hard & wear-resistant surface on
machine parts by the enrichment of the surface layer with carbon. The various machined parts are directly carburized after getting machined & after carburization they are sent for final grinding. There are various techniques of carburizing like – pack carburizing, gas carburizing & liquid carburizing. At gas carburizing in the electrical carburizing furnace is done. This operation is done at temperature 930-940C and in this mostly temperature depends upon the kinds of the materials of the products. The time required for complete this operation is 6 to 8 hours.
Quenching: Quenching is the method of rapid cooling of a metal in a bath of liquid during
heat treatment. It consists of quenching the products component from hardening temperature in the quenching medium. The component is allowed to cool up to temperatue of quenching bath. In addition to severe internal stresses, components also develop tendency towards distortion and cracking due to very high cooling rates involved in this process. Cooling rate can be 53 | Page
controlled by adopting less severe quenching media, say oil in place. This operation is done at temperature 830C and then quench in oil, keeps it cool in oil for 20 minutes.
Washing: After quenching, again the washing operation is done for removing oilness From the
manufactured product and preparing for the next operation. the manufactured product took in washing machine and wash the products at temperatue 250C very accurately. Time for done this operation is 10-15 minutes.
Tempering: during the quenching operation , the hardness value is reaches near about 70-80
and we required the harness value 60, according to the instructions of engineer. So we acheiving the required hardness value tempering operation is on the manufactured porducts. This operation is done at temperature 170C and time required for complete this operation is 90 minutes.
Shot Peening After the pre-heat treatment processes, the next operation is shot peening. It is similar as that of shot blasting, this operation is used for removing extra materials and provide finishing. Time required for doing this operation is 15 minutes and shot grade is S-230.
Induction Hardening The Induction hardening is a surface hardening process in which the surface layers of the metal are hardened but a relatively soft core is maintained. The induction hardening is achieved by passing a high frequency alternating current through the work-piece which is placed in an inductor coil. The alternating current generates a magnetic field of equal intensity but of reverse polarity. Thus, the current penetrates & the surface of the piece is hardened but a soft core remains.
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Fig. Induction hardening
Case hardening Case hardening is the process of hardening the surface of a metal object while allowing the metal deeper underneath to remain soft, thus forming a thin layer of harder metal at the surface. For steel or iron with low carbon content, which has poor to no hardenability of its own, the case hardening process involves infusing additional carbon into the case. Case hardening is usually done after the part has been formed into its final shape, but can also be done to increase the hardening element content of bars to be used in a pattern welding or similar process. Flame or induction hardening are processes in which the surface of the steel is heated to high temperatures (by direct application of a flame, or by induction heating) then cooled rapidly, generally using water; this creates a "case" of martensite on the surface. A carbon content of 0.3–0.6 wt% C is needed for this type of hardening.
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INSEPECTION AND TESTING
Vernier Scale A vernier scale is a device that lets the user measure more accurately than could be done by reading a uniformly-divided straight or circular measurement scale. It is scale that indicates where the measurement lies in between two of the marks on the main scale.
Fig. Vernier scale
Micrometer A micrometer sometimes known as a micrometer screw gauge, is a device incorporating a calibratedscrew used widely for precise measurement of small distances in mechanical engineering and machining as well as most mechanical trades, along with other metrological. Micrometers are usually, but not always, in the form of calipers, which is why micrometer caliper is another common name. The spindle is a very accurately machined screw. The object to be measured is placed between the spindle and the anvil. The spindle is moved inward by turning the ratchet knob or thimble until the object to be measured is lightly touched by both the spindle and the anvil.
Fig, Micrometer
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The sleeve through which the spindle moves is graduated with marks 0.025 inch (0.635 mm) apart, with the number 1 on the sleeve representing 0.1 inch (2.54 mm), 2 representing 0.2 inch complete turn for each 0.025 inch on the sleeve scale, and the thimble scale is graduated from 0 to 25. Thus use of the two scales permits a reading to the nearest 0.001 inch (0.025 mm).
Plug gauge These gauges are referred to as plug gauges; they are used in the manner of a plug. They are generally assembled from standard parts where the gauge portion is interchangeable with other gauge pieces and a body that uses the collet principle to hold the gauges firmly. To use this style of gauge, one end is inserted into the part first and depending on the result of that test, the other end is tried.
Fig. Plug gauge In figure, the top gauge is a thread gauge that is screwed into the part to be tested, the labeled GO end will enter into the part fully, the NOT GO end should not. in plug gauge used to check the size of a hole, the one end is the GO and another endis NOT GO.
Snap gauge Snap gauges are often used when a large quantity of work pieces must be inspected. The snap gauge has four anvils or jaws, the first one or pair (outermost) are set using the upper limit (tolerance) of the part and the inner set adjusted to the lower limit of the part. A correctly machined part will pass the first set of jaws and stop at the second — end of test. In this manner a part may be checked in one action, unlike the plug gauge that needs to be used twice and flipped to access the second gauge.
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Fig. Snap gauge
Dial Test Indicator A dial test indicator, also known as a lever arm test indicator or finger indicator, has a smaller measuring range than a standard dial indicator. A test indicator measures the deflection of the arm, the probe does not retract but swings in an arc around its hinge point. The lever may be interchanged for length or ball diameter, and permits measurements to be taken in narrow grooves and small bores where the body of a probe type may not reach. The model shown is bidirectional, some types may have to be switched via a side lever to be able to measure in the opposite direction. These indicators actually measure angular displacement and not linear displacement; linear distance is correlated to the angular displacement based on the correlating variables
Fig. Dial indicater
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Magnaflux Testing
When metal parts are manufactured, especially those parts that involve the transportation industry, they must withstand a through testing of integrity. These types of tests must not destroy the parts that have been manufactured. A systematic examination called nondestructive testing was developed. Included in these series of checks is the magnaflux or magnetic dye test
Fig. Manaflux testing
Significance
Metal parts when they are machined and/or welded can become stressed during those processes. Those stresses can reveal themselves in the from of small fissures or cracks in the metal joints. These stress fractures at times may be difficult to see with the human eye. A method of employing small magnetic particles and a fluorescent dye was implemented to highlight any abnormalities of the machining and joining those metal parts.
Features
After the part is sprayed with the magnetic particle dye solution, a handheld electro magnet is passed over the part. The magnetic field causes the small particles in the solution to align themselves with that magnetic field. Generally if the part being tested has no small fissures or cracks, the magnetic particles simply lay on the surface.
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Identification
A testing part that does contain a crack or fracture will hold the solution in that small fissure, and once the magnetic field is passed over the area, a "line" of particles will form. This identification line will fill into the fissure and the particles will remain in place due to the magnetic field that was induced.
Some fissures are so small that it may be difficult to identify the abnormality with the human eye. The dye that is employed in the testing solution is a fluorescent base. This liquid fluorescent base is readily seen under a black light illumination source. Typically the magnaflux light test is performed in a darkened area so the black light illumination can be seen.
Lead and Profile Tester In this the lead and profile is checked of a gear and spline. Correctness in lead & profile of gears & splines leads to proper meshing of pitch point & power transmission of one gear to other gear.
Fig. Lead and profile tester
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Rolling Tester Gear rolling test is generally included in final acceptance test. A gear tested on Double Flank Gear Tester is normally the indication of good running properties of the gear and is adequate assurance about the quality of gear.The readings taken are the validation of center distance between two gears to be inspected or between one gear and one master gear meshing without backlash during one complete rotation of gear.
Fig Rolling tester
Rockwell scale
Fig. Rockwell scale
The Rockwell scale is a hardness scale based on indentation hardnessof a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. There are different scales, 61 | Page
denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA. When testing metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers.
Operation : The determination of the Rockwell hardness of a material involves the application of a minor load followed by a major load, and then noting the depth of penetration, vis a vis, hardness value directly from a dial, in which a harder material gives a higher number. The chief advantage of Rockwell hardness is its ability to display hardness values directly, thus obviating tedious calculations involved in other hardness measurement techniques.
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MAINTENANCE Maintenance involves fixing any sort of mechanical plumbing or electrical device should it become out of order or broken. It also includes performing routine actions which keep the device in working order or prevent trouble from arising .
Types of Maintenance
Break-down maintenance :The long term continously working on the machines, the machine
parts & its components gets damaged or breakdowndue to wear & tear or due to over running. The problems may occur due to electrical faults, over-running, noise or vibration etc. We should check the machines regulerly on time before working on it. Preventive maintenance : The care and servicing by personnel for the purpose of maintaining
equipment and facilities in satisfactory operating condition by providing for systematic inspection, detection, and correction of incipient failures either before they occur or before they develop into major defects. Corrective maintenance : Corrective maintenance is a task performed to identify, isolate, and
rectify a fault so that the failed equipment, machine, or system can be restored to an operational condition within the tolerances or limits established for in-service operations.
Condition-based
maintenance:
Condition-based
maintenance
shortly
described,
is
maintenance when need arises. This maintenance is performed after one or more indicators show that equipment is going to fail or that equipment performance is deteriorating. It was introduced to try to maintain the correct equipment at the right time.
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