Introduction to Coputer Aided Manufacturing

Introduction to Coputer Aided Manufacturing

1. Computer Aided Design and Manufacturing DR. SACHIN MAHESHWAR DEPARTMENT OF MECHANICAL ENGINEERING GOVT. ENGG . COLLEGE ABAD

2. contents MODULE 1: Introduction concept of CAD/CAM. MODULE 2: Computer system, Hardware in computer – Aided Design system, Product cycle Automation , part programming.

3. contents MODULE 3: Computer aided design system software, Transformation, geometric modelling , Drafting applications. MODULE 4: CAD/CAM technology to finite element data preparation , Concept of data structures.

4. contents MODULE 5: NC, CNC, DNC programming. MODULE 6: Introduction to AVG.

5. DR. SACHIN MAHESHWAR DEPARTMENT OF MECHANICAL ENGINEERING GOVT. ENGG . COLLEGE ABAD Introduction concept of CAD/CAM.

6. Design- Manufacturing Process (Before computer era) Sketch with Pencils

7. Design- Manufacturing Process (Before computer era) Engineering Drawing with Pencils

8. Design- Manufacturing Process (Before computer era) Manufacturing

9. Design- Manufacturing Process (With computer)

10. Learning Outcomes Identify the various input and output devices used in CAD/CAM systems .

11. INTRODUCTION CAD/CAM: The use of computers to aid design and manufacturing process. It is a term which means computer-aided design and computer- aided manufacturing. It is the technology concerned with the application of computers to the manufacturing of engineering components, from the drawing phase to the production phase, to quality control department and to the warehouse.

12. Computer-aided design (CAD) CAD can be defined as the use of computer systems to assist in the following: C reation Modification, Analysis , Optimization of a design

13. Conti… The computer systems consist of the hardware and software to perform the specialized design functions required by the particular user user/firm. CAD hardware includes : Computer Graphics display terminals Keyboards Other Peripheral equipment's. CAD software includes : Computer programs ( implement computer graphics on the system) Application programs(facilitate the engineering functions of the user )

14. Computer-aided manufacturing (CAM) CAM can be defined as the use of computer systems to plan, Manage and Control the operations of a manufacturing plant Either direct or indirect computer interface with the plant's production resources.

15. CAM Computer aided Manufacturing (CAM) is the use of computer software to control machine tools and related machinery in the manufacturing of work pieces. Cam is a subsequent computer aided process after CAD and sometimes CAE.

16. Historical background WW-II: The need for more complex and precise machining was originated for military aerospace industry. 1950s: Development of NC machines. 1960s: Development of SKETCHPAD BY MIT, 1 ST GUI. 1970s: As digital computers were invented, 2D drafting CAD software's were developed.

17. Historical background The first true 3D CAD/CAM (computer-aided manufacturing) program was created between 1966 and 1968 by Pierre Bézier , an engineer at Renault . 1980s: As digital computers became more advance and economical, solid modeling 3D CAD software were developed. Late 1980s: CAD softwares became more advance , by the addition of Analysis tool.

18. Product cycle PRODUCT CONCEPT DESIGN ENGINEERING DRAFTING PROCESS PLANNING PRODUCTION SCHEDULING PRODUCTION QUALITY CONTROL CUSTOMER FEEDBACK CUSTOMER MARKET NEED FORECAST

19. TRADITIONAL DESIGN PROCESS RECOGNITION OF NEED PROBLEM DEFINITION SYNTHESIS ANALYSIS & OPTIMIZATION EVALUATION PRESENTATION

20. Processes involved in problem identification

21. Processes involved in problem definition

22. ANALYSIS & OPTIMIZATION

23. APPLICATION OF COMPUTERS FOR DESIGN RECOGNITION OF NEED PROBLEM DEFINITION SYNTHESIS ANALYSIS & OPTIMIZATION EVALUATION PRESENTATION GEOMETRIC MODELING ENGINEERING ANALYSIS DESIGN REVIEW & EVALUATION AUTOMATED DRAFTING

24. Product cycle IN COMPUTERISED ENVIRONMENT PRODUCT CONCEPT COMPUTER AIDED DESIGN (PRODUCT PROVING) SIMULATION COMPUTER AIDED PROCESS PLANNING Computer aided CNC part program generation COMPUTER AIDED QUALITY CONTROL CUSTOMER FEEDBACK CUSTOMER MARKET NEED FORECAST GEOMETRIC MODELING FINITE ELEMENT ANALYSIS CNC M/c Actual production COMPUTER AIDED SCHEDULING COMPUTER AIDED WORK STANDARD S COMPUTER AIDED DRAFTING COMPUTER AIDED TOOL DESIGN TOOL MANUFACTURING ORDER NEW EQUIPMENT MATERIAL REQUIREMENT PLANNING CAD CAM

25. Learning objectives To  identified  the functions and requirements of  geometric  modeling  in  manufacturing. study the different types of geometric  modeling  techniques  . recognize the different types geometric  entities and its mathematical representations 

26. Geometric modelling Geometric modeling is a branch of applied mathematics and computational geometry that studies methods and algorithms for the mathematical description of shapes. Geometric modelling is the representation of physical objects on computers , allowing both interactive and automatic analysis of design, and the expression of design in a form suitable for manufacturing. Today most geometric modeling is done with computers and for computer-based applications

27. Functions  of Geometric  Modelling   Design  Analysis  Evaluation of areas and  volumes Evaluation  of inertia  properties Interference  checking and assemblies  Interference checking and  assemblies Analysis  of tolerance build‐up in  assemblies Analysis  of kinematics – machines, robotics Automatic  mesh generation for FEA

28. FUNCTIONS OF GEOMETRIC MODELLING Manufacturing Parts   classification Process   planning Numerical  control data generation and  verification Robot program generation Production Engineering Bill of materials • Material requirement • Manufacturing resource requirement • Scheduling  Inspection and Quality Control Program generation for inspection machines Comparison of produced part with design

29. Geometric Modeling Conceptual design FEM Analysis Kinematics Analysis Shape optimization Assembly Computer Aided Inspection Computer Numerical Control

30.   types of computer geometric modeling techniques Wire frame models  (describe an object using boundary lines) Surface models  (describe an object using boundary surfaces) Solid models  (describe an object as a solid )

31. CAD Hardware The hardware of CAD system consists of following: CPU Secondary memory Workstation Input unit Output unit Graphics display terminal

32. Central Processing Unit (CPU)

33. ALU ALU DATA INPUT A DATA INPUT B DATA OUTPUT C Function inputs STATUS OUTPUTS

34. Work Station

35. The work station is a visible part of the CAD system which provides interaction between the operator and the system . A work station can be defined as a station of work with its own computing power to support major software packages, multitasking capabilities demanded by increased usage , complex tasks and networking potential with other computing environments.

36. The workstation must accomplish five functions: l. It must interface with the central processing unit. 2. It must generate a steady graphic image for the user. 3. It must provide digital descriptions of the graphic image. 4. It must translate computer commands into operating functions. 5. It must facilitate communication between the user and the system A typical interactive graphics workstation would consist of the following hardware Components : A graphics terminal Operator input devices

37. Image generation in computer graphics The graphic display technologies include: CRT (cathode ray tube) Liquid crystal display Plasma panel display Nearly all computer graphics terminals available today use the cathode ray tube (CRT) as the display device. Television sets use a form of the same device as the picture tube.

38. A heated cathode emits a high-speed electron beam onto a phosphor-coated glass screen. 'The electrons energize the phosphor coating, causing it to glow at the points where the beam makes contact. By focusing the electron beam, changing its intensity, and controlling its point of contact against the phosphor coating through the use of a deflector system, the beam can be made to generate a picture on the CRT screen.

39. GRAPHICAL DISPLAYS The graphical display enables the user to view images and to communicate with the displayed images by adding, deleting, blanking and moving graphics entities on the display screen . The graphics display can be divided into two types based on the scan technology used to control the electron beam when generating graphics on the screen . Random scan Raster scan

40. Random scan In random scan, graphics can be generated by drawing vectors or line segments on the screen in a random order

41. Raster scan In random scan, the screen is scanned from left to right, top to bottom, all the time to generate graphics.

42. Various types of CRT displays are broadly categorized into : 1.Directed-beam refresh 2. Direct-view storage tube (DVST) 3. Raster scan (digital TV)

43. Input Devices Input devices are used to input two possible types of information: text and graphics. Text-input devices and the alphanumeric keyboards. There are two classes of graphics input devices: Locating devices : Locating devices, or locators, provide a position or location on the screen. Ex: light pens, mouse, digitizing tablets, joysticks, trackballs , thumbwheels , touchscreen and touchpads. Locating devices typically operate by controlling the position of a cursor on screen . Thus, they are also referred to as cursor-control devices.

44. Scanners Keyboards Digitizing Tablets Mouse Joy sticks & Trackballs

45. HARDCOPY PRINTERS AND PLOTTERS Printers and plotters are used to create check plots for offline editing and producing final drawings and documentation on paper. Printers usually provide hard copies of text as well as graphics. Printers are classified as follows on the basis of three principal technologies used for their operation : Impact dot matrix printer Ink jet printer Laser printer

46. Impact dot matrix printer

47. Ink jet printer

48. Laser printer

49. COMPUTER GRAPHICS SOFTWARE AND DATA BASE The graphics software is the collection of programs written to make it convenient for a user to operate the computer graphics system . The software must be written specifically for the type of CRT and the types of input devices used in the system . Newman and Spoull list six ground rules that should be considered in designing graphics software: Simplicity . The graphics software should be easy to use. Consistency . The package should operate in a consistent and predict-able way to the user .

50. Completeness . There should be no inconvenient omissions in the set of graphics functions. Robustness . The graphics system should be tolerant of minor instances of misuse by the operator. Performance . Within limitations imposed by the system hardware, the performance should be exploited as much as possible by software. Graphics programs should be efficient and speed of response should be fast and consistent. Economy . Graphics programs should not be so large or expensive as to make their use prohibitive.

51. SOFTWARE CONFIGURATION In the operation of the graphics system by the user, a variety of activities take place, which can be divided into three categories: l . Interact with the graphics terminal to create and alter images on the screen 2 . Construct a model of something physical out of the images on the screen. 3 . Enter the model into computer memory and/or secondary storage.

52. The graphics software can be divided into three modules according to a conceptual model suggested by Foley and Van Dam : l . The graphics package (Foley and Van Dam called this the graphics system) 2 . The application program 3. The application data base

53. SOFTWARE CONFIGURATION Application data base Application Program Graphics Package Graphics Terminal User input Devices

54. FUNCTIONS OF A GRAPHICS PACKAGE Generation of graphic elements Transformations Display control and windowing functions Segmenting functions User input functions

55. TRANSFORMATIONS Many of the editing features involve transformations of the graphics elements or cells composed of elements or even the entire model . Two-dimensional transformations To locate a point in a two-axis Cartesian system, the x and y coordinates are specified . These coordinates can be treated together as a lxl matrix: ( x,y ). For example , the matrix (2, 5)

56. Using the rules of matrix algebra, a point or line (or other geometric element represented in matrix notation) can be operated on by a transformation matrix to yield a new element . There are several common transformations used in computer graphics. TRANSLATION SCALING ROTATION

57. Translation involves moving the element from one location to another. x' =x + m, y' = y + n where x', y' = coordinates of the translated point x, y = coordinates of the original point m, n = movements in the x and y directions, respectively In matrix notation this can be represented as (x', y') = (x, y) + T

58. Translations Moving an object is called a translation. We translate a point by adding to the x and y coordinates , respectively , the amount the point should be shifted in the x and y directions. We translate an object by translating each vertex in the object . P 2 = P 1 +T , T= Tx Ty P 2 =(X 1 + Tx ) (Y1+Ty)

59. SCALING : Scaling of an element is used to enlarge it or reduce its size. We scale an object by scaling the x and y coordinates of each vertex in the object. P2 = S P1 S = ( Sx 0) ( Sy ) P1 = ( x1 ) ( y1 ) P2 = ( Sx X1 ) ( Sy Y1 )

60. The points of an element can be scaled by the scaling matrix as follows: (x' ,y') = ( x,y )S Where S= If the scaling factors are less than I, the size of the element is reduced and it is moved closer to the origin. The scaling need not necessarily be done equally in the x and y directions. Example: a circle could be transformed into an ellipse by using unequal x and y scaling factors.

61. ROTATION : Rotation About the Origin: To rotate a line or polygon, we must rotate each of its vertices . From the illustration we know that : sin (A + B) = y2/r, cos (A + B) = x2/r and sin A = y1/r , cos A = x1/r X1,y1 X2,y2 r A B

62. From the double angle formulas: sin (A + B) = sinAcosB + cosAsinB and cos (A + B)= cosAcosB – sinAsinB Substituting : y2/r = (y1/r) cosB + ( x1/r) sinB ,y2 = y1cosB + x1sinB And x2 = x1cosB - y1sinB P2 = R P1 (x2) ( cosB - sinB ) ( x1) ( y2 ) ( sinB cosB ) ( y1 )

63. ROTATION : In this transformation, the points of an object are rotated about the origin by an angle . For a positive angle, this rotation is in the counterclockwise direction . This accomplishes rotation of the object by the same angle, but it also moves the object. In matrix notation, the procedure would be as follows: ( x',y ') = ( x,y )R Where R=  

64. Ex: Line defined by (1,2) and (1,4) a) It is desired to translate the line in space by 2 units in the x direction and 3 units in y direction. b) rotate the line about the origin by 30 0 . c) scaling the line by factor 2.

65. Ans : Representation of Line in matrix form T=

66. Homogeneous Coordinates The rotation of a point, straight line or an entire image on the screen, about a point other than origin, is achieved by first moving the image until the point of rotation occupies the origin, then performing rotation, then finally moving the image to its original position. The moving of an image from one place to another in a straight line is called a translation. A translation may be done by adding or subtracting to each point, the amount, by which picture is required to be shifted. Translation of point by the change of coordinate cannot be combined with other transformation by using simple matrix application. Such a combination is essential if we wish to rotate an image about a point other than origin by translation, rotation again translation.

67. To combine these three transformations into a single transformation, homogeneous coordinates are used. In homogeneous coordinate system, two-dimensional coordinate positions (x, y) are represented by triple-coordinates. Homogeneous coordinates are generally used in design and construction applications. Here we perform translations, rotations, scaling to fit the picture into proper position . Example of representing coordinates into a homogeneous coordinate system :  For two-dimensional geometric transformation, we can choose homogeneous parameter h to any non-zero value. For our convenience take it as one. Each two-dimensional position is then represented with homogeneous coordinates (x, y, 1).

68. Homogeneous matrix

69. Composite Transformation A number of transformations or sequence of transformations can be combined into single one called as composition. The resulting matrix is called as composite matrix. The process of combining is called as concatenation . The enlargement with respect to center.

70. Step-1 The object is translated so that its center coincides with the origin as in fig Step2:  Scaling of an object by keeping the object at origin is done in fig Step3:  Again translation is done . This second translation is called a reverse translation.

71. Scaling with a fixed point A problem with the scale transformation is that it also moves the object being scaled . Scale a line between (2, 1) (4,1) to twice its length.

72. Concatenating – affine transformations by multiplying together – sequences of the basic transformations ➔ define an arbitrary transformation directly – ex) three successive transformations

73. P1=AP P2= BP1 Q=CP2 Q= CBP1= CBAP

74. Transformation is not commutative – Order of transformation may affect transformation position Associative properties: A.B.C=A.(B.C)=(A.B).C So Find the composite transformation matrix

75. General two-dimensional Pivot-point rotation – Graphics package provide only origin rotation – Perform a translate-rotate-translate sequence • Translate the object to move pivot-point position to origin • Rotate the object • Translate the object back to the original position

76. General Fixed-Point Scaling

77. Problem Reflect the triangle defined by (2,5),(5,10) and (2,10) about a line y=(1/2)(x+4).

78. 3D Transformation Translation transformation

79. Scaling transformation

80. 3D rotation 3D rotation is done around a rotation axis Fundamental rotations – rotate about x, y, or z axes Counter-clockwise rotation is referred to as positive rotation Rotation about z – similar to 2D rotation

81. Rotation about y: z -> y, y -> x, x->z

82. Rotation about x

83. Numerical Control Numerical control can be defined as a form of programmable automation in which the process is controlled by numbers, letters, and symbols . NC technology has been applied to a wide variety of operations, including drafting , assembly , inspection, sheet metal press working, and spot welding.

84. BASIC COMPONENTS OF AN NC SYSTEM 1.Program of instructions 2. Controller unit, also called a machine control unit (MCU) 3. Machine tool or other controlled process

85. Program of instructions CAD & CAM The program of instructions is the detailed step-by-step set of directions which tell the machine tool what to do. It is coded in numerical or symbolic form on some type of input medium that can be interpreted by the controller unit . The most common input medium l-in.-wide punched tape punched cards, magnetic tape, and even 35-mm motion picture film

86. There are two other methods of input to the NC system manual entry of instructional data to the controller unit (MDI). The second other method of input is by means of a direct link with a computer .(DNC) Part programming: A part programmer plans the process for the portions of the job to be accomplished by NC. They are responsible for planning the sequence of machining steps to be performed by NC and to document these in a special format.

87. There are two ways to program for NC: Manual part programming Computer-assisted part programming In manual part programming, the machining instructions are prepared on a form called a part program manuscript. The manuscript is a listing of the relative cutter / workpiece positions which must be followed to machine the part.

88. In computer-assisted part programming , much of the tedious computational work required in manual part programming is transferred to the computer. This is especially appropriate for complex work-piece geometries and jobs with many machining steps

89. Controller unit CU consist of the electronics and hardware that read and interpret the program of instruction and convert it into mechanical actions of the machine tool. The typical elements of a conventional NC controller unit include the tape reader, a data buffer, signal output channels to the machine tool, feedback channels from the machine tool, and the sequence controls to coordinate the overall operation of the foregoing elements.

90. All modern NC systems today are sold with microcomputer as the controller unit. This type of NC is called computer numerical control ( CNC) Machine tool or other controlled process The third basic component of an NC system is the machine tool or other controlled process . It is the part of the NC system which performs useful work. In the most common example of an NC system, one designed to perform machining operations, the machine tool consists of the worktable and spindle as well as the motors and controls necessary to drive them .

91. NC PROCEDURE

92. NC COORDINATE SYSTEMS NC machine tool axis system for milling and drilling operations. NC machine tool axis system for turning ope ration .

93. Fixed zero and floating zero The programmer must determine the position of the tool relative to the origin (zero point) of the coordinate system. NC machines have either of two methods for specifying the zero point. The first possibility is for the machine to have a fixed zero. In this case, the origin is always located at the same position on the machine .

94. The second and more common feature on modern NC machines allows the machine operator to set the zero point at any position on the machine table. This feature is called floating zero. The part programmer is the one who decides where the zero point should be located. The decision is based on part programming convenience . For example, the work part may be symmetrical and the zero point should be established at the center of symmetry.

95. Absolute positioning and incremental positioning

96. COMMONLY USED WORD ADDRESSES N-CODE: Sequence number, used to identify each block with in an NC program and provides a means by which NC commands may be rapidly located. It is program line number. It is a good practice to increment each block number by 5 to 10 to allow additional blocks to be inserted if future changes are required. • G-CODE: Preparatory Word, used as a communication device to prepare the MCU. The G-code indicates that a given control function such as G01, linear interpolation, is to be requested . X , Y & Z-CODES: Coordinates. These give the coordinate positions of the tool.

97. F-CODE: Feed rate. The F code specifies the feed in the machining operation. • S-CODE : Spindle speed. The S code specifies the cutting speed of the machining process. • T-CODE : Tool selection. The T code specifies which tool is to be used in a specific operation. • M-CODE : Miscellaneous function. The M code is used to designate a particular mode of operation for an NC machine tool. I , J & K-CODES: They specify the centre of arc coordinates from starting.

98. M codes vary from machine to machine depending on the functions available on it. They are decided by the manufacturer of the machine.

99. G00 Rapid traverse When the tool being positioned at a point preparatory to a cutting motion , to save time it is moved along a straight line at Rapid traverse , at a fixed traverse rate which is pre-programmed into the machine's control system. Typical rapid traverse rates are 10 to 25 m /min., but can be as high as 80 m/min . Syntax: N005 [G90/G91] G00 X10 Y10 Z5

100. G01 Linear interpolation (feed traverse) Syntax: N050[G90/G91 ] G01 X10 Y10 Z5 F25

101. G02/G03 Circular interpolation G 0r M code N__ G02/03 X__ Y__Z__ I__ J__K__ F__ using the arc center or N__ G02/03 X__ Y__Z__ R__ F__ using the arc radius Arc center The arc center is specified by addresses I, J and K. I, J and K are the X, Y and Z co-ordinates of the arc center with reference to the arc start point. G02 moves along a CW arc

102. G90 ABSOLUTE POSITION COMMAND G91 INCREMENTAL POSITION COMMAND G 17 G18 G19 : PLANE SELECTION G 70 Inch data input G 71 Metric data input

103. Manual Part Programming Example Tool size = 0.25 inch, Feed rate = 6 inch per minute, Cutting speed = 300 rpm, Tool start position: 2.0, 2.0 Programming in inches

104. [email protected]

105. Any Query

106. AUTOMATION AND CAD/CAM Automation is defined as the technology concerned with the application of complex mechanical, electronic, and computer-based systems in the operation and control of production . Production activity can be divided into four main categories: l. Continuous-flow processes 2 . Mass production of discrete products 3 . Batch production 4 . Job shop production.

107. Four production types related to quantity and product variation CONTINUOUS FLOW PROCESS MASS PRODUCTION BATCH PRODUCTION JOB SHOP PRODUCTION PRODUCTION VOLUME PRODUCT VARIETY