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Computer Aided Design and Manufacturing (CAD/CAM)

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  1. Computer Aided Design and Manufacturing (CAD/CAM) Kartik Chandra Bhagat Assistant Professor RTC INSTITUTE OF TECHNOLOGY, RANCHI JHARKHAND

  2. Terminology CAD (Computer Aided Design): CAD is application of computers and graphics software to aid or enhance the product design from conceptualization to demonstration (The use of computer methods to develop the geometric model of the product in 3-D form, such that the geometric and manufacturing requirements can be examined). CADD (Computer Aided Design and Drafting): Combining the CAD function with drafting to generate the production drawings of the parts for the purpose of the down stream processing. CAE (Computer Aided Engineering): the use of computer methods to support basic error checking analysis, optimization, manufacturing etc. of product design.

  3. CAM (Computer Aided Manufacturing): Effective use of computer technology in manufacturing planning and control (The computer software used to develop the computer numerical control part programs). CIM (Computer Integrated Manufacturing): It is the phrase used to describe the complete automation of a manufacturing plant, with all processes functioning under computer control and digital information tying them together. CAP (Computer Aided Planning): The use of computer for many of the planning function such as material requirement planning, computer aided scheduling etc. CAPP: (Computer Aided Process Planning): The use of computer to generate the process plans for the complete manufacture of the product and parts. CATD (Computer Aided Tool Design): Computer assistance to be used for developing the tools for manufacture of products and parts.

  4. Computer System A computer's processing unit executes a series of instructions that make it read, manipulate and then store data. Conditional instructions change the sequence of instructions as a function of the current state of the machine or its environment. A computer is a general purpose device which can be programmed to carry out a finite set of arithmetic or logical operations. Conventionally, a computer consists of at least one processing element and some form of memory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit that can change the order of operations based on stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved.

  5. Computer Aided Design (CAD) Use of computer systems to assist in the creation, modification, analysis, and optimization of a design

  6. CAD tools Definitions of CAD tools based on their constituents

  7. Computer Application Hardware Software CAD Input devices System Utilities Programming CAD/CAM O.S. Interrupter GKS CPU APT Editor Basic PHIGS Debugger Output devices • IGES Prolog FEM Linker VDI Compiler DBMS VDM Low level High level • NAPLPS Virtual Device Interface/ Metafile Initial Graphics Exchange Specifications North American Presentation-Level Protocol Syntax Programmers Hierarchical Interactive Graphics System V.B. C / C++ PASCAL Assembler FORTRAN

  8. Hardware Components: A. Input devices A1. Keyboard: - A keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys: function keys, numeric key, navigation keys pad A2. Mouse: -A mouse is a small device used to point to and select items on your computer screen. It's small, oblong, and connected to the system unit by a long wire that resembles a tail. Some newer mice are wireless.

  9. A3. Joystick: - A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. 1. stick, 2. base, 3. trigger, 4. extra buttons, 5. auto fire switch, 6. throttle, 7. hat switch (POV hat), 8. suction cup. A4. Image scanner : - An image scanner is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. A5. Webcam : - A webcam is a video camera that feeds its images in real time to a computer or computer network, often via USB, Ethernet, or Wi-Fi.

  10. A6. Graphics tablet :- A graphics tablet (also digitizer, digitizing tablet, graphics pad, drawing tablet or pen tablet) is a computer input device that enables a user to hand-draw images and graphics, similar to the way a person draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures. It can also be used to trace an image from a piece of paper which is taped or otherwise secured to the surface. Capturing data in this way, either by tracing or entering the corners of linear poly-lines or shapes is called digitizing. A7. Microphone:- A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. Microphones are used in many applications such as telephones, tape recorders, karaoke systems, hearing aids, motion picture production, live and recorded audio engineering, FRS radios, megaphones, in radio and television broadcasting and in computers for recording voice, speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic checking or knock sensors.

  11. A8. Lightens :- The light pen is intrinsically a pointing device that enables the user to select a displayed graphics item on a screen by directly touching its surface in the vicinity of the item. It allows the user to point to displayed objects or draw on the screen in a similar way to a touch screen but with greater positional accuracy. It was long thought that a light pen can work with any CRT-based display, but not with LCDs. A9. Fingerprint recognition:- Fingerprint recognition or fingerprint authentication refers to the automated method of verifying a match between two human fingerprints. Fingerprints are one of many forms of biometrics used to identify individuals and verify their identity. This article touches on two major classes of algorithms (minutia and pattern) and four sensor designs (optical, ultrasonic, passive capacitance, and active capacitance).

  12. A10. Touch screen :- A touch screen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touch screens can also sense other passive objects, such as a stylus. Touch screens are common in devices such as game consoles, all-in-one computers, tablet computers, and smart phones. The touch screen has two main attributes. First, it enables one to interact directly with what is displayed, rather than indirectly with a pointer controlled by a mouse or touchpad. Secondly, it lets one do so without requiring any intermediate device that would need to be held in the hand (other than a stylus, which is optional for most modern touch screens). Such displays can be attached to computers, or to networks as terminals. They also play a prominent role in the design of digital appliances such as the personal digital assistant (PDA), satellite navigation devices, mobile phones, and video games.

  13. A11. Digital camera:- A digital camera (or digicam) is a camera that takes video or still photographs by recording images on an electronic image sensor. Most cameras sold today are digital and digital cameras are incorporated into many devices ranging from PDAs and mobile phones (called camera phones) to vehicles. Digital and film cameras share an optical system, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The diaphragm and shutter admit the correct amount of light to the imager, just as with film but the image pickup device is electronic rather than chemical. However, unlike film cameras, digital cameras can display images on a screen immediately after being recorded, and store and delete images from memory. Many digital cameras can also record moving video with sound. Some digital cameras can crop and stitch pictures and perform other elementary image editing.

  14. A12. 3D Scanner:- A 3D scanner is a device that analyzes a real-world object or environment to collect data on its shape and possibly its appearance (i.e. color). The collected data can then be used to construct digital, three dimensional models. Many different technologies can be used to build these 3D scanning devices; each technology comes with its own limitations, advantages and costs. Many limitations in the kind of objects that can be digitized are still present, for example, optical technologies encounter many difficulties with shiny, mirroring or transparent objects. Collected 3D data is useful for a wide variety of applications. These devices are used extensively by the entertainment industry in the production of movies and video games. Other common applications of this technology include industrial design, orthotics and prosthetics, reverse engineering and prototyping, quality control/inspection and documentation of cultural artifacts.

  15. A13. Laser rangefinder:- A laser rangefinder is a device which uses a laser beam to determine the distance to an object. The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender. Due to the high speed of light, this technique is not appropriate for high precision sub-millimeter measurements, where triangulation and other techniques are often used. A14. Barcode reader:- A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.

  16. B. The Central Processing Unit (CPU) The CPU is the hardware within a computer system which carries out the instructions of a computer program by performing the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. A CPU has four main components: the arithmetic logic unit (ALU), the control unit (CU), the memory (M), and the input and output devices (I/O). These parts are interconnected by busses, often made of groups of wires. The ALU, performs arithmetic and logical operations, and the CU, extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.

  17. B1. Arithmetic logic unit: - The ALU is a digital circuit which is capable of performing two classes of operations: arithmetic and logic. The set of arithmetic operations that a particular ALU supports may be limited to addition, subtraction, multiplication, division, trigonometry functions such as sine, cosine, etc., and square roots. Some can only operate on whole numbers (integers) whilst others use floating point to represent real numbers, albeit with limited precision. However, any computer that is capable of performing just the simplest operations can be programmed to break down the more complex operations into simple steps that it can perform. Therefore, any computer can be programmed to perform any arithmetic operation—although it will take more time to do so if its ALU does not directly support the operation. An ALU may also compare numbers and return Boolean truth values (true or false) depending on whether one is equal to, greater than or less than the other. Logic operations involve Boolean logic: AND, OR, XOR and NOT.

  18. B2. Control Unit (CU) :- The control unit manages the computer's various components; it reads and interprets (decodes) the program instructions, transforming them into a series of control signals which activate other parts of the computer. Control systems in advanced computers may change the order of some instructions so as to improve performance. The control unit is the circuitry that controls the flow of data through the processor, and coordinates the activities of the other units within it. In a way, it is the "brain within the brain", as it controls what happens inside the processor, which in turn controls the rest of the computer. The examples of devices that require a control unit are CPUs and graphics processing units (GPUs). The modern information age would not be possible without complex control unit designs. The control unit receives external instructions or commands which it converts into a sequence of control signals that the control unit applies to the data path to implement a sequence of register-transfer level operations.

  19. B.3 Memory :- Memory is the ability to store, retain, and recall information and experiences. Computer memory refers to physical devices used to store data and sequences of instructions (programs) on a temporary or permanent basis, typically distinguished as fast random-access memory and relatively slow data storage. The term primary memory is used for the information in physical systems which are fast (i.e. RAM), as a distinction from secondary memory, which are physical devices for program and data storage which are slow to access but offer higher memory capacity. Primary memory stored on secondary memory is called "virtual memory“.

  20. Primary Memory: System RAM speed is controlled by bus width and bus speed. Bus width refers to the number of bits that can be sent to the CPU simultaneously, and bus speed refers to the number of times a group of bits can be sent each second. A bus cycle occurs every time data travels from memory to the CPU. Secondary Memory: - Secondary memory stores information on a hard disk, a rigid platter or stack of platters with a magnetic surface. Because hard disks can hold massive amounts of information, they usually serve as computer's primary means of storage, holding almost all of programs and files.

  21. Microprocessor:- A microprocessor executes a collection of machine instructions that tell the processor what to do. Based on the instructions, a microprocessor does three basic things: • Using its ALU, a microprocessor can perform mathematical operations like addition, subtraction, multiplication and division. • A microprocessor can move data from one memory location to another. • A microprocessor can make decisions and jump to a new set of instructions based on those decisions.

  22. Output Devices:1. Printer: - A printer transfers data from a computer onto paper. The two main types of printers are inkjet printers and laser printers. Inkjet printers are the most popular printers for the home. They can print in black and white or in full color and can produce high-quality photographs when used with special paper. Laser printers are faster and generally better able to handle heavy use. 2. Speakers: - Speakers are used to play sound. They may be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.

  23. Graphics Displays:- The graphics display of work station is considered its most important component because the quality of the displayed image influences the perception of generated design on the CAD/CAM system. In addition to viewing image, the graphics display enables the user to communicate with the displayed image by adding, subtracting, deleting, blanking and moving graphics entity on the displayed screen. 3. Monitor:- A monitor displays information in visual form, using text and graphics. The portion of the monitor that displays the information is called the screen. Like a television screen, a computer screen can show still or moving pictures. There are two basic types of monitors: CRT (cathode ray tube) monitors and LCD (liquid crystal display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and lighter. CRT monitors, however, are generally more affordable.

  24. 3.1Cathode ray tube (CRT):- CRT is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. • In television sets and computer monitors, the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image is produced by controlling the intensity of each of the three electron beams, one for each additive primary color (Red, Green, and Blue) with a video signal as a reference. • Cutaway rendering of a color CRT: • Three Electron guns (for red, green, and blue phosphor dots) • Electron beams • Focusing coils • Deflection coils • Anode connection • Mask for separating beams for red, green, and blue part of displayed image • Phosphor layer with red, green, and blue zones • Close-up of the phosphor-coated inner side of the screen Shadow mask color CRT Aperture grille color CRT

  25. Refresh Vector Display:- Deflection system Character generator Text font Input Device Phosphor coating Refresh buffer memory Display file Display Processor X-Position CRT Display Input Command Data Y-Position CPU (host) Vector generator

  26. Direct View Storage:- Deflection system Character generator Text font Input Device Phosphor storage mesh Display Processor X-Position CRT Display Input Command Data Y-Position CPU (host) Vector generator

  27. Image refresh system Direct View Storage (DVST):- Color Raster Display with eight planes Color map cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) Rasterizer Phosphor Pixel BGR Deflection and color system Display Processor Input devices CRT Image display system Display Input Command Data CPU (host)

  28. Image refresh system Direct View Storage (DVST):- Color Raster Display with eight planes Color map cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) cell P Pixel values in memory (bit map) Rasterizer Phosphor Pixel BGR Deflection and color system Display Processor Input devices CRT Image display system Display Input Command Data CPU (host)

  29. Thin Film Transistor (TFT) TFT is a type of LCD flat-panel display screen, in which each pixel is controlled by from one to four transistors. The TFT technology provides the best resolution of all the flat-panel techniques, but it is also the most expensive. TFT screens are sometimes called active-matrix LCDs. • TFT is a special kind of field-effect transistor made by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate. A common substrate is glass, since the primary application of TFTs is in liquid crystal displays. This differs from the conventional transistor where the semiconductor material typically is the substrate, such as a silicon 1 - Glass plates 2/3 - Horizontal and vertical polarizer's 4 - RGB color mask 5/6 - Horizontal and vertical command lines 7 - Rugged polymer layer 8 - Spacers 9 - Thin film transistors 10 - Front electrode • 11 - Rear electrodes

  30. Liquid Crystal Display (LCD) & Light Emitting Diode (LED) Screen:- LCD & LED screen both is a liquid crystal display. An LCD display has two layers of glass that are polarized and joined together, the liquid crystals then pass or block the light to display the picture. The crystals do not produce any light as the light comes from a series of lamps at the back of the screen. On an LCD screen, the lamps at the back of the screen are Hot Cathod Fluorescent Lamps (HCFL), whilst on an LED TV the lights at the back of the screen are Light Emitting Diodes (LED). There are two types of LED methods used to provide the back lighting to the screen: edge lighting and full array lighting.  Majority of LEDs fall in the edge-lit without local dimming category, with the LEDs placed only along the edge of the LCD panel.

  31. Raster Display:- Typical Pixel Matrix of Raster Display M Y Wh C Y R G B Pixel B G X Bl R Hue: VIBGYOR. Pixels: The smallest element of the picture / image. Resolution: The quality of the picture/image (10x8). Color depth: The number of bit stored per pixel. Aspect ratio: The ratio between horizontal to vertical frame (5:4). Black Pure White Shade Tint Tone

  32. Resolution:- The resolution are the number of pixel presents along the entire length and width of an image/ picture. The size of the image/ picture is known as frame. The resolution are two distinctly different terms image resolution and screen resolution. Image resolution refers to the pixel spacing of an image/picture i.e. the distance from one pixel to next pixel. It is measured by PPI. The screen resolution is refer to the internal surface of the monitor screen which is coated with RGB phosphor material that glows when struck by a stream of electron. The coated material is arranged into an array of million of tiny cells RGB usually called dots. The dots pitch is the distance between adjacent sets of RGB dots. It is measured by DPI: the shortest distance between any two dots of same color. Refresh rate:- The screen image is "refreshed" many times per second. Refresh rates are measured in Hertz (HZ), which means "times per second". Video RAM:- All video cards have some RAM. How much depends on the desired colour depth. Video cards usually have 1, 2 or 4 MB RAM for normal usage.

  33. Rasterization:-Most of the raster scan display are used in monitor and therefore the graphics software will have to provide the necessary component of that as part of the software. This involves the conversion of the vectorial information of the drawing into its equivalent raster format such that the frame buffer can be fitted with that information. This process is termed as rasterization and involves one of the most important and basic components of a graphics software. Graphics system Monitor Application data structure / model Graphics system Kernal (core) system Device driver Application Program Input S E

  34. Most of the raster graphics display devices are operated through a digital frame buffer. This frame buffer stores a matrix of pixel, intensity values, which is called memory bank. • Colour depth:- The number of memory bit require to store colour information (intensity values for primary RGB colour) about a pixel is called colour/bit depth. Each pixel can display a number of different colours. Colour depth is measured in bits. Colour depth: • Describes the amount of storage per pixel. • Also indicates the number of colors (intensity values for primary RGB colour) available.

  35. 80’s 2000’s 90’s 2010’s High-definition (HD) Video:- HD video refers to any video system of higher resolution than standard-definition (SD) video, and most commonly involves display resolutions of 1,280×720 pixels (720p) or 1,920×1,080 pixels (1080i/1080p).

  36. Common high-definition video modes Extra high-definition video modes

  37. Prob.1. An eight-plane raster display has a resolution of 1280x1024 and a refresh rate of 60 Hz noninterlaced. Find The RAM size of the bit map (refresh buffer) The time required to display a scan line and pixel. The active display area of the screen if the resolution is 80 dpi. The optimal design if the bit map size is to be reduce by half. Soln. The RAM size of the bit map = 8x1280x1024=1.25Mb The time required to display a scan line Ts = 1/60*1024=16.2 microsecond. The time required to display a pixel = 16.2/1280 = 12.7 nanosecond. The active display area = 1280/80= 16 inch horizontal & 1024/80=12.8 inch vertical. The optimal design if the bit map size is to be reduce by half = 640x512 display.

  38. Prob.1. How can you draw a 500 pixel wide square on a 1280x1024 vertical screen whose aspect ratio is 4:3? Soln. H+500,V+533 H,V+533 (500x1024x4) / (1280x3) = 533.33 H+469,V+500 H,V+500 H,V H+500,V (500x1280x3) / (1024x4) = 468.75 H,V H+469,V

  39. Aliasing • Distortion of information due to under-sampling • Aliasing is cause by the discrete nature of pixels (Sampling Error). • Approximation of lines and circles with discrete points often gives a • staircase appearance or "Jaggies".

  40. Anti-Aliasing Aliasing is a fact of any computer image which depth on a grid of finite number of pixel in the horizontal and vertical direction. It can not be eliminated, but its visually irritating obviousness can be minimized, at a piece of course. Since we’re representing real-world objects with a finite number of pixels, aliasing occurs frequently. Therefore, we need to implement techniques to cancel the undesirable effects of aliasing. These techniques are called anti-aliasingtechniques. Two approaches are available: Higher screen resolution: To increase the number of the resolutions, it needs a huge frame buffer Antialiasing technique (a) Super sampling (b) Area sampling (c) Pixel phasing (d) Dithering (e) Line Intensity Differences

  41. Anti-aliasing Techniques: Vary pixel intensities along boundaries to smooth the edge. • 1. Super sampling: Compute intensities at sub-pixel grid positions and combine the results to obtain the pixel intensity. • 2. Area sampling • 2.1 Unweighted area sampling: a). Find pixel intensity by calculating the areas of overlap of each pixel within the objects to be displayed. • b). Pixel intensity is proportional to the amount of area covered. • 2.2 Weighted area sampling: Define a weighting function that determines the influence on the intensity of the pixel. • Pixel phasing: Lines are smoothed by moving the electron beam to a closer approximate of the mathematical line. Pixel positions can be shifted by a fraction of a pixel diameter (1/4, 1/2, or 3/4) to plot points closer to the mathematical line. • Dithering: Combining pixel of available colour • Line Intensity Differences: The diagonal line appears less bright than the horizontal. (The diagonal line is longer than the horizontal line by a factor of sqrt(2)). Total intensity is proportional to their length.

  42. Super-Sampling: • Split single pixel into sub-pixels. • Pixel’s final color is a mixture of sub-pixels’ colors. • Simple method: Sample at the middle of each sub-pixel. Then, pixel’s color is the average of the sub-pixels’ color. Pixels Sub-divide into sub-pixels

  43. Divide each single pixel into sub-pixels. • The number of intensities are the max number of sub-pixels selected on the line segment within a pixel. 1.1 Super-Sampling a Zero-Width Line: Apply Bresenham’s algorithm at sub-pixel level Sub-divide each pixel into sub-pixels, for example 4x4 sub-pixels Each pixel can have a maximum of 4 colored sub-pixels 0.0 0.0 0.0 1.0 0.5 1.0 1.0 0.0 0.5 0.0 0.0 0.0 0 0 0 4 2 4 4 0 2 0 0 0 Assign color How many sub-pixels are colored? Fraction of pixel’s color to be line’s color

  44. 1.2 Super-Sampling a Line with Non-Zero Width • The intensity level for each pixel is proportional to the number of sub-pixels inside the polygon representing the line area. • Line intensity is distributed over more pixels. A line that is one-pixel wide. For every pixel: Maximum number of sub-pixels inside line = 16 A sub-pixel is considered in if its lower-left corner is inside the line 0 0 5/16 9/16 10/16 15/16 13/16 7/16 8/16 2/16 0 0 Fraction of sub-pixels are in = fraction of color of the pixel should be line color

  45. 2.1 Unweighted area sampling: The intensity of a pixel decreases as the distance between the pixel centre and the edge increases. The primitive must intersect the pixel to have some effect. Equal areas contribute equally to the pixel intensity. Intensity of a pixel is proportional to its area covered by the line

  46. 2.2 Weighted area sampling • Equal areas can contribute to unequal intensity. • Circular pixel geometry. • Sub-pixel Weighting Masks Instead of considering each sub-pixel to be of equal importance, assign a weight to each sub-pixel. Usually consider the center sub-pixel to be most important 1 2 2 1 2 3 3 2 2 3 3 2 1 2 2 1 Example weight for each sub-pixel Total weight = 32 Final color of pixel = Sum of each (sub-pixel colors x sub-pixel weight) / total weight

  47. 2.2 Weighted area sampling: Common Filter Functions Box Filter Cone Filter 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 3 2 1 2 4 5 4 2 3 5 6 5 3 2 4 5 4 2 1 2 3 2 1

  48. 4 Dithering: Display two or more pixels around the computed location in varying intensities rather then, a single pixel at the rounded off location . Let straight line equation: y = 0.3 x +39 CEG Pixel Intensity values for Anti-aliasing for a line

  49. Additional Benefit of Anti-Aliasing • Solve the line-intensity difference problem. • The line-intensity difference occurs when we’re drawing a diagonal line. • In the following example, 5 pixels are used to draw each line, but the diagonal line is actually longer. Therefore, the diagonal line appears less intense. • Applying anti-aliasing technique automatically takes care of this problem (assume anti-alias non-zero width line).