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  2. Syllabus(ME-101-F) • Section-A • Introduction to machine tools • Basic Concepts of thermodynamics • Properties of steam & steam generators • Section-B • Refrigeration & Air conditioning. • Hydraulic turbines & pumps. • Section-C • Power transmission methods & devices • Stresses & strains • Section-D • Introduction to manufacturing system(NC & CNC Machining) For more info. :

  3. Topics • Introduction to Manufacturing Systems • Fundamentals of Numerical Control (NC) • Advantage of NC systems • Classifications of NC • Comparison of NC and CNC For more info. :

  4. (1)Manufacturing system • A manufacturing system may be defined as a collection of integrated equipments & human resources whose function is to perform one or more processing or assembly operations on raw material, part or set of parts. For more info. :

  5. (1.1)Examples of manufacturing system • A team of workers producing tyre in production line. • Worker working in an assembly plant & assembling the engine. • Worker working on one machine ,which operates on semi-automatic cycle. For more info. :

  6. (1.2)Main components of manufacturing system • Production machines. • Material handling system. • Computer system • Human resource. For more info. :

  7. (1.2.1)production machines • Machines can be classified as: • Manually operated:-which provides for operation & worker provides the,lathe,milling machines. • Semi automatic:-it performs the portion of work cycle under some form of program control,& human worker tends to machine for the remaining cycle,by loading & unloading it.ex.,CNC Lathe • Fully Automatic :-it has the capacity to operate for extended period of time with no human attention. A worker is not required to be present during each cycle.ex.,A fully automatic injection moulding machine. For more info. :

  8. (1.2.2)material handling system • These includes: • Loading & unloading of work units.-it involves moving work units into the machine • Positioning the work units.-it involves placing the part in a known location & orientation • Transporting work units.-it means work transport between the stations. • A temporary storage which ensures that work is always present for stations. For more info. :

  9. 1.2.3)computer controlled system • This funtion includes:- • Communicate instructions to the workers. • Download part program to computer controlled machines. • Material handling system control. • Schedule production. • Quality control. • Failure diagnosis. For more info. :

  10. 1.2.4)Human resources • In manufacturing systems,humans performs some or all of the value added work that is accomplished on the parts or products. For more info. :

  11. (1.3)Classification of manufacturing system • Type of operation performed • Processing operation • Assembly operation • Number of work stations • One station • Many stations • Level of automation • Manual • Semi-automatic • Fully automatic • Part or product variety • Identical units • Variations in work units For more info. :

  12. NC Machine For more info. :

  13. 2.)Fundamentals of Numerical Control(NC) • A Numerical Controlled machine is defined as machine that uses machine readable sets of codes that controls the activities used in its operation. • The coded instructions consist of numbers, letters of alphabets & symbols refer to specific distances , functions or motion that the machine tool can understand as it machines the workpiece . For more info. :

  14. 2.1)Components of NC system • software • Machine control unit • Machine tool For more info. :

  15. 2.1.1)software • The programs or set of instructions , languages, punched paper tapes & other such information processing items are refered to as a software. • The software controls the sequence of movement of tool. • Programming of the operations is executed manually. • The programmer plans the operation as sequence & writes the instuctions in the form of codes,known as part program. • These instructions are punched on a tape.tape reader reads the codes & sends it to MCU,which converts it into movement of the tool. For more info. :

  16. 2.1.2)Machine contol unit(MCU) • Every NC has a main unit which is known as MCU; • IT consist of electronic circuits called hardware that reads the NC Programe , interprets it & translate it for mechanical actions of the tool. • Main parts of MCU:- • Input unit • Memory • Processor • Output channels • Control panel. • Feed back channels & transducers For more info. :

  17. 2.1.3)Machine tool • The third part of numerical control system is the machine tool. • It is the output generating component of NC System. • Input is given in the form of part program.MCU transmits this programe of instructions to machine tool to generate relative motion between workpiece & cutting tool. For more info. :

  18. 3.)Advantages of NC • Greater accuracy & improved quality. • Consistency in quality:The same part can be reproduced to the same degree of accuracy. • Human error is minimum;few rejections & hence scrap is reduced. • Better utilisation of machine as idle time can be reduced • High production rates & reduced production cost per piece. • Operation of the machine does not require highly skilled labour. • Less physical participation of workers:increased safety & reduced risk of injury. For more info. :

  19. 3.) Advantages of NC(Contd…) • Easy & effective production planning. • Changes in part design can be incorporated easily,by simply changing the part program tape. • Reduced transportation cost:machining centre reduces the number of times a component has to be moved from one machine to other; • Reduced inspection:inspection cost is reduced due to reliability of NC machines. • Lesser scraps:the NC machine eliminates most of the human errors thereby reucing cost of scrap by 50%. • Reduced setup time. For more info. :

  20. Application on NC • It is used where complex & intricate parts are to be manufactured. • Components being manufactured are subjected to frequent design changes. • Low to medium batches of repetitive components are to be made with prescision. For more info. :


  22. 4.)Classification of NC • Based on type of motion • Point to point system • Straight line system • Continous path system(contouring) • Based on control loops • Open loop • Closed loop • Based on programming method. • Absolute programming • Incremental programming For more info. :

  23. Classification of NC(contd..)1. On the basis of type of motion • Point-to-point:- • Straight cut NC Tool path (parallel to X or Y-axis. Start point Start point Maching operation is performed at each point For more info. :

  24. Classification of NC(contd..)A.)On the basis of type of motion(contd…) • (iii)Contouring:- TOOL PATH For more info. :

  25. 4.1)based on type of motion • Point to point:-In this system,machine tool performs machining operation at selected positions & doesnot affect workpiece while moving from one point to other.ex:drilling holes. • Straight line system:-in this system,the tool moves at the controlled feed rate in one axis direction at a time. • Continous path NC:Itis a system in which motion is controlled on more than on axis movement of machine tool.The path of cutter is continously controlled to generate desired geometry. For more info. :

  26. Classification of NC(contd..)2.)Based on the type of control system: a)Open loop control system b)Closed loop control system For more info. :

  27. 4.2)type of control loop • A)open loop system:-in this ,there is no feed back or return signal to provide the information to controller about the effect of signal that is produces.It has no system of checking wheter the servomotor has accurately moved the machine slides to the programmed distance • B)CLOSED LOOP SYSTEM:-it has a feedback built into the system , which monitors the position of the tool. The output i.e, distance is measured & compared to the programed distance. For more info. :

  28. 4.3)programming method • Absolute programming:-In this system, all the dimensions are given from a common datum or zero point. • Incremental programming:-In this each dimension is taken from the past position & not from the common datum. For more info. :

  29. CNC • CNC may be defined as NC system in which dedicated, stored programe computer is used to perform some or all of basic numerical control functions. • In CNC,programe is entered once & stored in computer’s memory • In CNC,the computer allows the following: • Storage of additional programs. • Program editing • Running of program from memory. • Machine & control diagnostics. • Incremental/absolute switching. For more info. :

  30. 5.)Comparision of NC & CNC For more info. :