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Manufacturing Technology - 2

by Siva Chari
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Siva Chari
Siva Chari
ME 6402 MANUFACTURING TECHNOLOGY – II LTPC 3003 OBJECTIVE To understand the concept and basic mechanics of metal cutting, working of standard machine tools such as lathe, shaping and allied machines, milling, drilling and allied machines, grinding and allied machines and broaching To understand the basic concepts of computer numerical control (CNC) machine tool and CNC programming. UNIT I THEORY OF METAL CUTTING 9 Introduction: material removal processes, types of machine tools – theory of metal cutting: chip formation, orthogonal cutting, cutting tool materials, tool wear, tool life, surface finish, cutting fluids. UNIT II CENTRE LATHE AND SPECIAL PURPOSE LATHES 9 Centre lathe, constructional features, cutting tool geometry, various operations, taper turning methods, thread cutting methods, special attachments, machining time and power estimation. Capstan and turret lathes – automats – single spindle, Swiss type, automatic screw type, multi spindle - Turret Indexing mechanism, Bar feed mechanism. UNIT III OTHER MACHINE TOOLS 9 Reciprocating machine tools: shaper, planer, slotter Milling: types, milling cutters, operations - Hole making : drilling - Quill mechanism , Reaming, Boring, Tapping Sawing machine: hack saw, band saw, circular saw; broaching machines: broach construction – push, pull, surface and continuous broaching machines UNIT IV ABRASIVE PROCESSES AND GEAR CUTTING 9 Abrasive processes: grinding wheel – specifications and selection, types of grinding process – cylindrical grinding, surface grinding, centreless grinding – honing, lapping, super finishing, polishing and buffing, abrasive jet machining Gear cutting, forming, generation, shaping, hobbing. UNIT V CNC MACHINE TOOLS AND PART PROGRAMMING 9 Numerical control (NC) machine tools – CNC: types, constructional details, special features – design considerations of CNC machines for improving machining accuracy – structural members – slide ways –linear bearings – ball screws – spindle drives and feed drives. Part programming fundamentals – manual programming – computer assisted part programming. TOTAL: 45 PERIODS TEXT BOOKS 1. Hajra Choudry, “Elements of Work Shop Technology – Vol. II”, Media Promoters. 2002 2. HMT – “Production Technology”, Tata McGraw-Hill, 1998. 34 REFERENCES: 1. Rao, P.N. “Manufacturing Technology”, Metal Cutting and Machine Tools, Tata McGraw–Hill, New Delhi, 2003. 2. P.C. Sharma, “A Text Book of Production Engineering”, S. Chand and Co. Ltd, IV edition, 1993. 3. Shrawat N.S. and Narang J.S, „CNC Machines‟, Dhanpat Rai & Co., 2002. 4. P.N.Rao, „CAD/CAM Principles and Applications‟, TATA Mc Craw Hill, 2007. 5. M.P.Groover and Zimers Jr., „CAD/CAM‟ Prentice Hall of India Ltd., 2004. 6. Milton C.Shaw, „Metal Cutting Principles‟, Oxford University Press, Second Edition, 2005. 7. Rajput R.K, „Atext book of Manufacturing Technology‟, Lakshmi Publications, 2007. 8. Philip F.Ostwald and Jairo Munoz, „Manufacturing Processes and systems‟, John Wiley and Sons, 9th Edition,2002. 9. Mikell P.Groover, „Fundamentals of Modern Manufacturing,Materials, Processes and Systems‟, John Wiley and Sons, 9th Edition,2007. 10. Chapman. W. A. J and S.J. Martin, Workshop Technology, Part III, Viva Books Private Ltd., 1998
UNIT - I THEORY OF METAL CUTTING UNIT - I THEORY OF METAL CUTTING 1.1 INTRODUCTION In an industry, metal components are made into different shapes and dimensions by using various metal working processes. Metal working processes are classified into two major groups. They are:  Non-cutting shaping or chips less or metal forming process - forging, rolling, pressing, etc.  Cutting shaping or metal cutting or chip forming process - turning, drilling, milling, etc. 1.2 1.2.1 MATERIAL REMOVAL PROCESSES Definition of machining Machining is an essential process of finishing by which work pieces are produced to the desired dimensions and surface finish by gradually removing the excess material from the preformed blank in the form of chips with the help of cutting tool(s) moved past the work surface(s). 1.2.2 Principle of machining Fig. 1.1 typically illustrates the basic principle of machining. A metal rod of irregular shape, size and surface is converted into a finished product of desired dimension and surface finish by machining by proper relative motions of the tool-work pair. Fig. 1.1 Principle of machining (Turning) Fig. 1.2 Requirements for machining 1.2.3 Purpose of machining Most of the engineering components such as gears, bearings, clutches, tools, screws and nuts etc. need dimensional and form accuracy and good surface finish for serving their purposes. Preforming like casting, forging etc. generally cannot provide the desired accuracy and finish. For that such preformed parts, called blanks, need semi-finishing and finishing and it is done by machining and grinding. Grinding is also basically a machining process. Machining to high accuracy and finish essentially enables a product:  Fulfill its functional requirements.  Improve its performance.  Prolong its service. 1.2.4 Requirements of machining The essential basic requirements for machining a work are schematically illustrated in Fig. 1.2. DEPT. OF MECH. ENGG. 1
MANUFACTURING TECHNOLOGY - II The blank and the cutting tool are properly mounted (in fixtures) and moved in a powerful device called machine tool enabling gradual removal of layer of material from the work surface resulting in its desired dimensions and surface finish. Additionally some environment called cutting fluid is generally used to ease machining by cooling and lubrication. 1.3 1.3.1 TYPES OF MACHINE TOOLS Definition of machine tool A machine tool is a non-portable power operated and reasonably valued device or system of devices in which energy is expended to produce jobs of desired size, shape and surface finish by removing excess material from the preformed blanks in the form of chips with the help of cutting tools moved past the work surface(s). 1.3.2 Basic functions of machine tools Machine tools basically produce geometrical surfaces like flat, cylindrical or any contour on the preformed blanks by machining work with the help of cutting tools. The physical functions of a machine tool in machining are:  Firmly holding the blank and the tool.  Transmit motions to the tool and the blank.  Provide power to the tool-work pair for the machining action.  Control of the machining parameters, i.e., speed, feed and depth of cut. 1.3.3 Classification of machine tools Number of types of machine tools gradually increased till mid 20th century and after that started decreasing based on group technology. However, machine tools are broadly classified as follows: According to direction of major axis:  Horizontal - center lathe, horizontal boring machine etc.  Vertical - vertical lathe, vertical axis milling machine etc.  Inclined - special (e.g. for transfer machines). According to purpose of use:  General purpose - e.g. center lathes, milling machines, drilling, machines etc.  Single purpose - e.g. facing lathe, roll turning lathe etc.  Special purpose - for mass production. According to degree of automation:  Non-automatic - e.g. center lathes, drilling machines etc.  Semi-automatic - capstan lathe, turret lathe, hobbing machine etc.  Automatic - e.g., single spindle automatic lathe, swiss type automatic lathe, CNC milling machine etc. According to size:  Heavy duty - e.g., heavy duty lathes (e.g. ≥ 55 kW), boring mills, planning machine, horizontal boring machine etc.  Medium duty - e.g., lathes - 3.7 ~ 11 kW, column drilling machines, milling machines etc.  Small duty - e.g., table top lathes, drilling machines, milling machines.  Micro duty - e.g., micro-drilling machine etc. According to blank type:  Bar type (lathes).  Chucking type (lathes).  Housing type. 2
UNIT - I THEORY OF METAL CUTTING According to precision:  Ordinary - e.g., automatic lathes.  High precision - e.g., Swiss type automatic lathes. According to number of spindles:  Single spindle - center lathes, capstan lathes, milling machines etc.  Multi spindle - multi spindle (2 to 8) lathes, gang drilling machines etc. According to type of automation:  Fixed automation - e.g., single spindle and multi spindle lathes.  Flexible automation - e.g., CNC milling machine. According to configuration:  Stand alone type - most of the conventional machine tools.  Machining system (more versatile) - e.g., transfer machine, machining center, FMS etc. 1.3.4 Specification of machine tools A machine tool may have a large number of various features and characteristics. But only some specific salient features are used for specifying a machine tool. All the manufacturers, traders and users must know how machine tools are specified. The methods of specification of some basic machine tools are as follows: Centre lathe:  Maximum diameter and length of the jobs that can be accommodated.  Power of the main drive (motor).  Range of spindle speeds and range of feeds.  Space occupied by the machine. Shaper:  Length, breadth and depth of the bed.  Maximum axial travel of the bed and vertical travel of the bed / tool.  Maximum length of the stroke (of the ram / tool).  Range of number of strokes per minute.  Range of table feed.  Power of the main drive.  Space occupied by the machine. Drilling machine (column type):  Maximum drill size (diameter) that can be used.  Size and taper of the hole in the spindle.  Range of spindle speeds.  Range of feeds.  Power of the main drive.  Range of the axial travel of the spindle / bed.  Floor space occupied by the machine. Milling machine (knee type and with arbor):  Type; ordinary or swiveling bed type.  Size of the work table.  Range of travels of the table in X - Y - Z directions.  Arbor size (diameter).  Power of the main drive.  Range of spindle speed.  Range of table feeds in X - Y - Z directions.  Floor space occupied. DEPT. OF MECH. ENGG. 3

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