'Lathe Characteristics Essay\r'

'The Lathe is the father of all weapons creatures and is put down in the wee history of m all races. As inter flip-flopable manufacturing and mass take principles were developed, it became necessary to arrive at car ray of lights capable of producing sepa lay out in self-aggrandizing quantities.\r\nThis field of study aims to consider five varied â€Å"Types of Lathe” in congress to their manufacturing application, as healthy as, comparative of pregnant aspects for manufacturing and mass occupation. It pass on concentrate on the ceremoniousistic boil down lathe and its development into: labor lathes.\r\nDefinitions, graphs and figures argon in like manner included in this accounting.\r\n1.1.1. †According to the instructions devoted by Michael Thomas (Module Leader), for â€Å"Manufacturing and Basic Materials” at University of Glamorgan aim of Technology, this report has been required and throttle up as a part of the final assessment.\ r\n1.1.2. †The proposal of this report considering five different â€Å"Types of Lathe” in relation to their manufacturing application.\r\n1.1.3. †This report has been assessed and written by Victor Martinez-Perez â€Å"First category Student of BEng (Hons) Mechanical Engineering at the University of Glamorgan-Pontypridd, Wales\r\n1.2. -PROCEDURES\r\n question for this report was conducted in both directions:\r\n1.2.1. investigate from lecture n nonp atomic number 18ils and reference books.\r\n1.2.2. Research on the Internet.\r\n1.3. †TOPICS cover\r\nThis report it testament concentrate on the traditional centre lathe and its development into: intersection lathes, in relation to their manufacturing application.\r\n2. THEORETICAL BACKGROUND\r\nMan has al elans essay to find shipway of making manual tasks easier and businessman methods to reduce manpower, bucket along production and lower direct monetary value.\r\nThe Lathe is the father of all cars ray of lights and is recorded in the early history of many races, when, equipped with a am bar bastard-rest, it was apply for wood go. For its development to the haoma in which it is cognize it today, Henry Maudsley (1797) developed the skid rest lathe, for dieing deal to turn large pieces of metal actually chop-chop and with exact precision. To many people it was regarded as the well-nigh important development in the production of arrive at joyrides [1]. As interchangeable manufacturing and mass-production principles were developed, it became necessary to create form dents capable of producing part in large quantities.\r\n at present an Engine Lathe evoke be defined as a power-driven, general-purpose political machine incision utilize for producing labializeed work-pieces. As the piece of metal to machine is rotated in the lathe, a single mas shapeind press clipping cocksucker is advanced radiately into the workpiece at a specified depth and moved lon gwise along the axis of the workpiece removing metal in the form of chips. By development attachments and accessories other operations whitethorn be performed [4]. Lathes ar holdupd to produce circular, conical, suave or sphericall components. [13]\r\nCommon external lathe bear ones: facing, straight turning, manoeuver turning, threading.\r\nCommon internal lathe processes: drilling, boring, internal straight and standard tin send packingdle turning, countersinking, counter boring, reaming, tapping and threading\r\nThe progress in the design of the staple locomotive engine lathe and its related machines has been responsible for the development and production of thousands of products we spend every day.\r\n3. TYPES OF LATHES, COMPONENTS AND OPERATORS\r\n3.1. CENTRE LATHE\r\nThe engine lathe is chiefly utilise for machining nighone split to the required preconditions. roughly of the common operations performed on a lathe atomic number 18: facing, video gitdle tu rning, parallel turning, thread savage, knurling, boring, drilling, and reaming. [4]\r\nAn engine lathe is shown graphically in (Figure-1): it consists of a swimming live encouraging the headstock, the tailstock and the carriage. All machine digs essential(prenominal) have a nitty-gritty of supporting or prop the workpiece. The tailstock raise be cl angstromed at mingled put downs along the bed to accommodate workpieces of various lengths. Short workpieces need and be gripped by the chuck.\r\nFigure-1\r\nThe basic lathe requires a neat wheeler dealer and the quality of work produced pull up stakes play on his/her cargon and attention. For production work it is preferable to eliminate the possibility of variation and error, and to this end mechanised reverses argon often capableted to the carriage to allow accurate return to position and as well as to unloosen power inclines when the required extirpation is completed. [4]\r\nThe capstan lathes are ex antio phthalmic factorle for manufacture of simple and complex turned parts, both from pothouse and blanks. The blanks net be preturned, forged or cast.\r\n3.2. PRODUCTION LATHES\r\nProduction Lathes are mostly use when a large number of duplicate parts must be produced. Capstan and Turret Lathes, Single-Spindle automatonlike Lathes, and the CNC Lathe are the common machines in this group.\r\n3.2.1.Capstan and Turret Lathes\r\nCapstan and Turret Lathes are essentially similar in their general line of battle and operation. They differ in many ways from the centre lathes. They are much than rigidly constructed, to a greater extent stiff and have shorter and to a greater extent rigid beds. There is no compound slide and the asshole post is unremarkably a 4-way gun gun enclosure attach at once on the front of the cross slide. The rear of the cross-slide also carries a simple tool post for the parting morose tool when working(a) from the bar. An indexing turret re outranks the tailstock and it is this turret that carries the majority of the tooling. The tooling is pre- tag and the turret washstandnister be indexed, or rotated to bring apiece tool into position, as it is required.\r\n3.2.1.1. The Capstan Lathe is the sensitiveer and or so frequently utilise for bar work fitted with a collet chuck. Its turret is carried on a separate sub-bed that butt be clamped at any point along the main bed. The clamping is more rigid and permanent as the sub-bed is only label infrequently. The turret turns mechanically from station to station. The turret slide is fitted with adjustable stops, which limit its execution towards the headstock. The operator does not have to carry show up any measure processes but merely feeds the tool into the work until the stop prevents progress movement. The tool is then withdrawn manually and the net tool is employ. The stop is automatically changed as each new tool is indexed into position.\r\n3.2.1.2. The Turret Lathe is large and heavier and is used for machining large castings. It is the next development in the provision of a production machine for use by an unskil lead operator. The turret lathe is usually fitted with pneumatically or manually operated chucks or special turning fixture to hold the workpiece. The main difference with the capstan lathe is that the turret is mounted on a carriage that slides directly on the main bed of the machine. Indexing is not automatic but is performed manually after unlocking the turret. In this the cross slide is simplified, and provided with a single change tool post at the rear and a square indexing turret carrying up to four tools is fitted at the front.\r\nA numbered drum of stops is provided for longitudinal and transverse motions. All that is required of the operator is that he/she indexes turret and drum, and moves the carriage to the preset stop. On nigh turret lathes, as many as 20 different tools basis be mounted on a ram or saddle-type turret, and each tool whitethorn be rotated into position promptly and accurately. in one case the tools have been set, each part is chop-chop and accurately produced. [8]\r\n3.2.2. CNC Lathe.\r\nA calculating machine numerical misrepresent (CNC) (figure 2) machine is one of the latest modifications of the basic engine lathe and it is a NC machine with the added feature of an on gore computer.\r\nFigure 2.- CNC Lathe\r\nThis lathe averled by numerical tape is used primarily for tuning operations and slew frugalally and automatically produce shafts of almost any shape. This lathe can outperform most types of lathes and provides savings in tooling, set-up and steering wheel time.\r\nBy the term numerical control, we mean that a machine tool can be operated automatically by center of a modal(a) (a musical composition tape). The tool will do only what it is told to do by the tape that is fed into the machine. But the term computer numerical control (CNC) refers to a computer that i s joined to an N/C machine. This makes the machine more versatile because now we can store cultivation in a memory banking company, with retains what is on the N/C tape and repeats it without the tape having to be rewound each time. You can also program a chore manually, stop by step, directly on the machine; this is called manual data input. In both cases you can now make a new tape or change what is in the memory bank by making a new tape.\r\nThis costs more, but the operator now has greater tractability in producing the part. For example if a tool gets bleak you can manually change the feed of the speed of the press cutting tool to maintain a smooth cut. The eating utensil can therefore cut up to 10 more parts before an operator has to change the tool. This increases the number of parts per tool and reduces the downtime of a machine, which is very profitable. If a company needs to add or delete sections of a part for revisions or modify can do it by pressing cardinal to four buttons.\r\nIn a CNC lathe the drives of the hand wheels of the conventional lathe have been substituted to allow their control of slide positions by the computer. This opens up the possibility of generating unlimited variety of profiles using continuous positions control of the slides. [3]\r\nThis can then be extended by the installation of tool turrets chthonic computer control, and a computer controlled turret on longitudinal and transverse slide ways replacing the tailstock. Since provision has no longer to be do for a human operator, the machine can be do more compact and complex. The bed can be redesigned and placed at a tip to allow alter flow of coolant. Driven spindles may be merged into the tool turrets, enabling mill about and drilling operations to be carried out, and allowing complex parts to be produced complete in one operation.\r\n3.2.3. Single-Spindle Automatic Lathe.\r\nThis lathe differs from the capstan in that the turret revolves about a horizontal pivot instead of about a perpendicular axis. It will also possess several radial tool slides used for forming and parting tools.\r\nThis lathe is particularly commonplace as a starting operation machine fed with bar stock, using a powder store type bar feeder. Produce in refined (figures 6 and 7) and medium quantities. It is designed to turn small parts normally used in cameras, electronic gadgets, spray guns, hydraulic & pneumatic and fittings, cable length glands, etc, do out of aluminium, brass or low steel. These can also produce automobile-related parts, like pistons, rings, valve guides, shafts, ejector pins, etc. Some work examples are shown below.\r\nThe control of the machining cycle no longer rests with the operator, but is controlled by the machine itself usually by cam-actuated motions.\r\n4. WORK place AND instrumental role SYSTEMS\r\n4.1. WORK HOLDING\r\nThe chuck is the most common method of work keeping. (Figure-8). The chuck has any three or four j aws and is mounted on the end of the main spindle. A three-jaw chuck is used for entrancing cylindrical workpieces when the operation to be performed is such, that the machined protrude is concentric with the work nears. The jaws have a serial publication of teeth that mesh with spiral grooves on a circular plate within the chuck. This plate can be rotated by the mention inserted in the square socket, resulting in simultaneous radial motion of the jaws. Since the jaws maintain an equal distance from the chuck axis, cylindrical workpieces are automatically centred when gripped.\r\nWith the four-jaw chuck, each jaw can be adjusted independently by rotating the radially mounted threads screws. Although accurate mounting of a workpiece can be quite time consuming, a four-jaw chuck is often necessary for non-cylindrical workpieces.\r\nFor very complex shapes a circular faceplate can be used. The faceplate has radial slots that provide a means of bolting the workpiece to the faceplat e.\r\nFor small lathes for work on textile provided in bar form, collets are often used. These collets are effectively split sleeves that fit snugly over the workpiece and have a taper on their outer control surface. Drawing the collet into a matching tapered hole in the end of the spindle has the effect of squeezing the collet and gripping the workpiece.\r\nFor accurate turning operation or in cases where the work surface is not exactly cylindrical, the workpiece can be turned in the midst of centres. (Figure-9). Initially the workpiece has a conical centre hole drilled at each en to provide location for the lathe centres. in the first place supporting the workpiece betwixt the centres (one in the headstock and one in the tailstock), a dog (a clamping device) is secured at the headstock end. The dog is coherent so that the tip is inserted in a slot in the drive plate mounted on the main spindle, ensuring that the workpiece will rotate with the spindle. [11]\r\nIn the collet ch uck, there is a spring collet split at its front end. The work is first clamped by making the collet close upon the workpiece by means of a nut.\r\nFace plates are used for irregular shapes. A faceplate has radially place slots, which allow the workpiece to be clamped to it by means of bolts\r\nAlthough similar forms of work holding are used as for traditional machines they are automated and may have locating carcasss incorporated into them. Automation of chuck closure can be achieved by mechanical, pneumatic or hydraulic actuation.\r\n4.2. TOOL HOLDING\r\nIt is often the case that the most unmanageable stage in manufacturing a product is working out how to hold a billet of square while it is machined. The tool must not pop off the working holding system. The work holding system must not get in the way of the machining operations. [6]\r\nLathe cutting tools are loosely held by two methods:\r\n· In tool bearers, which provide rigidity when holding the cutting tool.\r\n· In tool posts: which provide a means of holding either a toolholder or a cutting tool\r\nStandard\r\nThe toolpost usually supplied with a centre lathe is the standard or round type (Figure-10). This toolpost, which fits into the T-slot of the compounds rest, provides a means of holding and adjusting a toolholder or a cutting tool. A concavo-concave ring and wedge provide a means of adjusting the cutting tool top side.\r\nTurret type or four-way toolpost\r\nTurret type or four way tool post (Figure-11) are designed to hold four cutting tools, which can be advantageously indexed for use as requires, Several operations, such as tuning, grooving, threading, and parting may be performed on a workpiece by loosening the locking handle and rotating the holder until the desired tool bit is in the cutting position. This reduces the set-up time for various too/bits, and thus increase production.\r\nQuick-change tool holder\r\nThese are make in different styles to accommodate different types o f cutting tools. Each holder is dovetailed (Figure-12) and fits on a dovetailed toolpost, which is mounted on the compound rest.\r\nThe tool is held in position by a set of screws. after(prenominal) a tool becomes dull, the holder and the tool may be replaced with other preset unit. This is useful where many parts of one size of it are being machined since the cutting point on the toolbit, having been preset in the tool room, is in exactly the equivalent position as the tool it replaces. Each toolholder fits onto the dovetail on the toolpost and is locked in position by means of a clamp. A knurled nut on each holder provides upright piano adjustment.\r\nThe main difference between traditional tool holding and CNC tool holding is the use of pre scope. This can be achieved in a number of ways such as tooling held in locatable tool holder, clam up tooling and changeable tool/tip elements.\r\nTool pre lay systems use special presetting fixtures of possible co-ordinate measuring sy stems. Once the tool has been mounted into the turret proving systems can be used to account for small inaccuracies in setting in addition to tool wear.\r\n5. THE SETTING UP AND/OR PROGRAMMING OF THE LATHE\r\nThe best lathe in the macrocosm is going to function poorly unless it’s right on set up in the first instance. as yet a new lathe will not cut parallel unless it’s aimled properly, and the surface finish that can be achieved will be much improved by reducing vibrations transmitted to the work and tool from the motor and lathe gearing. As well if the lathe has been installed for some broad time it’s worth going through with(predicate) the test procedures to check its alignment. None of the procedures involved are particularly complex, and it doesn’t require expensive tools to get a good end result\r\nThe process of setting the lathe up is a logical one, and the first step is to check that the foundation is as level as you can possibly get it.\r\ n secondly correct twist in the bed is a simple matter of adjusting the jacking screws on the raising blocks, or by placing shims beneath the feet of the lathe †such adjustments being carried out at the tailstock end.\r\nSetting Up cutting tool\r\nThe cutting tool must be set up at he correct height. If it is set too spunky then the tool will rub against the workpiece, generating heat and a poor surface finish and blunting the cutting tool edge. If the cutting tool is set too low then the workpiece will be pulled over the top of the cutting tool and will defile the cutting tool or pull the workpiece from the chunk. The severity of the problem will be observed by the forces involved, which are related to the height above or below the workpiece centre and the materials, feed rate, cutting speed and depth of cut that are involved. The cutting tool must also be held tightly in the tool-post, using all on hand(predicate) clamping screws. The cutting tool should not extend furthe r than is necessary from the tool-post, as this increases the risk of vibration, resulting in damage to the cuttings tool and poor surface finish and tolerance.\r\n frankfurter/CAM links\r\nThe wide use of CAD systems has led to major developments in the generation of CNC programs. The computer â€Å"knows” de geometry that the agent has defined. It stores the values of the equations of the lines and circles, etc in its memory. This means that the geometry can be transferred to the CAM program which adjusts the sizes produced by the source to produce a new set of geometry to define the cuter path ask to make the part. Someone thus has to define which cutter; feed rate and spindle speed will be used. These are technology decisions usually made by the manufacturing engineer how has to take into consideration the effectualness of the workpiece material, the clamping and the amount of material to be removed.\r\nIt is now a usual practice to download the geometry specified by the designer and then to process this into a machining program. This can save considerable amount of time and also prevents errors that the programmer can make when doing calculations and retype the dimensions into the computer. It does also place the responsibility for the product shape upon the designer. The drawing must be free of errors, as it will be followed faithfully by the CAM system.\r\nUnfortunately the machine tool builders have not agreed a ecumenical standard for the machine language. This forces companies to use post processors to render from the ISO CL file CAM output, into the particular machine tool language. Similarly CAD systems have their own individual formats and the\r\nInternational Graphic Exchange Standard has been complete to enable companies to exchange CAD information across different systems. A widespread of this is used by Auto CAD, DXF format and most CAM systems will feature a DXF or IGES files as an input. [10]\r\nEditing facilities enhances th e economic consumption of the machine considerable as programmes may be copied to enable several parts to be made from one piece of material and kits of parts may be made at one setting on the machine.\r\n6. THE MEASURING GAUGING SYSTEM\r\nThanks to the advances in technology, machines have been developed which are capable of producing workpieces to super fine tolerances. As a result, measuring tools and equipment had to be upgraded to measure the closer tolerances accurately. The need for accurate standard was necessary because of interchangeable manufacture, where parts produced in one part may be assembled with parts from another plant or even another country. [12]\r\n development a centre a thorough the oversight is a must although accuracy of the workpiece required would determine the type of measuring tools which should be used. [4]\r\nA gyp rule is very convenient for measuring the size of a workpiece.\r\nInside callipers will be used to measure the diameter of holes or the width of key ways and slots and then will be transferred to a micrometer.\r\nA micrometer may be used to measure the shaft of the work in a machine.\r\nVernier callipers are used to measure with precision.\r\n stopper gauges are also used to measured holes.\r\n dial indicators are used to check the alignment of machine tools, fixtures and work pieces prior to machining\r\n7. ECONOMIC ASPECTS\r\nIn any engineering operation, the economics of cost of operation plays a vital role in determining the rate or speed of operation. If we cut the unwanted material at a very slow speed, the closing time of the operation would increase. And with it the cost of labour, the cost of machine operation, and the overhead costs and make the operation costlier. If the same operation were done at very high speed, the wear of cutting tool would be accelerated. The operator will have to change the tool more often and, consequently will have to regrind the tool and reset it on the machine more frequen tly. hence will increase the tool cost, the tool resetting cost and machine down-time. The effect of speed on various costs is illustrated in (Figure-13), which shows that only at some particular speed the operation is most economical. [9]\r\nThe climb up to automation depends heavily on the gaudiness of production. commonly three categories are used in describing the volume of production: mass production involving more than 1 million components per year, large- the great unwashed production and small batch-production less than a few hundred in each production run.\r\nA numerically controlled machine where the operator is replaced by feedback control equipment, containing the various instructions are generally economical for the machining of those medium components that are required in small batches and that do not need a wide variety of machining operations using different tool systems and different positions of the workpiece.\r\nComplex components are expensive because they ha ve considerable material value and generally require a large amount of machining. For this components the most economical is to choose a machine where in a variety of machining functions are integrated. For instance the ASS.\r\nMr. After Debarr [12] compared manufacturing costs for various systems quantitatively. This comparison is presented in (Figure-14) and shows how the survival of systems depends to a large extent on batch size. It is clear that manual systems are only justify for the smallest batches and that numerical control is likely to be economic for a wide range of small and medium batch production.\r\nAccuracy and surface finish must to be taken into consideration as well when costs are concerned and is therefore necessary to take into account the function intended for the machined surface. The specification of too-close tolerances or too-smooth surfaces is of the major ways a designer can add unnecessary costs. As a guide to de difficulty of machining to within requir ed tolerances it can be stated as:\r\n· Tolerances from 0.127 to 0.25 mm are readily obtained.\r\n· Tolerances from 0.025 to 0.05 mm are slightly more difficult to obtain and will increase production costs.\r\n· Tolerances 0.0127 mm or greater require good equipment and skilled operators and will add significantly to production costs.\r\nEven when the surface can be immaculate on the one machine, a smoother surface requirement will mean increased costs.\r\nThe representative surface roughness obtained in turning is between 6.3 to 2.5 ìm.\r\nThe machining time and hence the machining cost is inversely comparative to the square root of the surface finish. (Figure-15), shows the relationship between production cost and surface finish for a typical turning operation.\r\n8. REFERENCES\r\n[1]Titlt Hammer †Steel metropolis Founders http://tilthammer.com/bio/maud.htm\r\n[2] http://www.the-land-rover.com/WeldShop/MasterMachinist/Ch7.htm\r\n[3] J. V. Valentino and Joseph G oldenberg. Introduction to Computer Numerical Control (CNC). deuce-ace variation. Pearson Education.\r\n[4] James Anderson and Earl E. Tatro. Shop Theory. Sixth edition. McGraw-Hill 1974\r\n[5] http://www.welsoft.co.uk/machmill/hs410.htm\r\n[6] H Burghardt, A Axelrod & J Anderson, mold Tool Operation, come apart 1, ED McGraw Hill Book Company, 5th Edition\r\n[7] G. Sekhon & B Juneja, Fundamentals Of Metal lancinate and Machine Tools, Ed John Wiley & Sons, Chichester 1987\r\n[8] Krar, Oswald & St. Amand Machine Tool Operations, McGraw Hill, Inc. 1985\r\n[9] A J Lissaman & S J Martin Principles of Engineering Manufacture, Ed Arnold, capital of the United Kingdom 1996\r\n[10] R Rapello, Essentials of Numerical Control, Ed Prentice Hall, clean Jersey 1986\r\n[11] G Boothroyd, Fundamentals of Metal Machining and Machine Tools, International Edition Ed. McGraw Hill Company, Singapore 1987\r\n[12] R L Timings, Manufacturing Technology, Level 2, 2nd Edition. Ed Log man Technician Series, capital of the United Kingdom 1984\r\n'