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CAD/CAM


INTRODUCTION

Computer-aided design (CAD) is the use of computer systems to assist in the creation, modification, analysis, or optimization of a design.

Computer-aided manufacturing (CAM) is the use of computer systems to plan, manage, and control the operations of a manufacturing plant through direct or indirect computer interface with plant’s resources.


Need for CAD/CAM

• To increase productivity of the designer• To improve quality of the design• To improve communications• To create a manufacturing database• To create and test tool paths and optimize

them • To help in production scheduling and MRP

models• To have effective shop floor control


Implementation of a Typical CAD Process on a CAD/CAM system

Delineation of geometric

model

Definition translator

Geometric model

Design and Analysis

algorithms

Drafting anddetailing

Documentation

To CAM ProcessInterface algorithms

Design changes


CAD Tools Required to Support the Design Process

Design phase Required CAD toolsDesign conceptualization Geometric modeling techniques;

Graphics aids; manipulations; and visualization

Design modeling and simulation Same as above; animation; assemblies; special modeling packages.

Design analysis Analysis packages; customized programs and packages.

Design optimization Customized applications; structural optimization.

Design evaluation Dimensioning; tolerances; BOM; NC.

Design communication and documentation

Drafting and detailing…


Implementation of a Typical CAM Process on a CAD/CAM system

Geometric model

Interface

algorithms

Process planning

Inspection

Assembly

Packaging

To shipping and marketing

NC programs


Manufacturing phase Required CAM tools

Process planning CAPP techniques; cost analysis; material and tooling specification.

Part programming NC programming

Inspection CAQ; and Inspection software

Assembly Robotics simulation and programming

CAM Tools Required to Support the Design Process


Definitions of CAD Tools Based on Their Constituents

Computer graphics concepts

Design toolsGeometric modeling

CADtools


Definition of CAD Tools Based on Their Implementation in a Design Environment

Design tools + Computer

Hardware(control unit; display

terminals; I/O devices

Software (graphics; modeling; applications

programs

= CAD tools


Definitions of CAM Tools Based on Their Constituents

Networking concepts

Mfg toolsCAD

CAMtools


Definition of CAM Tools Based on Their Implementation in a Manufacturing

Environment

Mfg tools + Computer

Hardware(control unit; display terminals; I/O devices

Software (CAD; NC; MRP; CAPP…)

= CAM tools

Networking


Definitions of CAD/CAM Tools Based on Their Constituents

Mfg tools

Networking

Design tools

Geometric modeling

Computer graphics concepts

CAD/CAMtools


Definition of CAD/CAM Tools Based on Their Implementation in an Engineering Environment

Design andMfg tools

Hardware

Software = CAD/CAM tools

Networking

+ Computer


Geometric modeling of conceptual design

Is design evaluation Possible with

available Standard software?

Design testing And evaluation

Is final designApplicable?

Drafting

Documentation

Process planning

Are there manufacturing discrepancies in CAD databases?

NC programming

Machining

Inspection

Assembly

Develop customized programs and packages

No

Yes

Yes

Yes

Geometric modeling and graphics package

Design package

Programmingpackage

No

No

CAPP package

NCpackage

InspectionAnd Roboticspackage

Typical Utilization of CAD/CAM Systems in an Industrial Environment


The Manufacturing Process

The Design Process

Synthesis Analysis The CAD Process

The CAM Process

Design needs

Design definitions, specifications, and requirements

Collecting relevant design information and feasibility study

Design conceptualization

Design modeling and simulation

Design analysis

Design optimization

Design evaluation

Design documentation and communication

Process planning

Order materials

Design and procurement of new tools

Production planning

NC, CNC, DNC programming

Production

Quality control

Packaging

Marketing

Shipping

Typical Product Life Cycle


System hardware 4.3.2 OVERVIEW OF PENTIUM PCThe hardware of a Pentium computer consists of the following:i. Mother boardii. Hard disc/floppy disc controller cardiii. Graphics adapter cardiv. Input/Output cardv. Switch mode power supplyvi. Floppy disc drivevii. Hard disc driveviii. CD-ROM drive


GRAPHICS SYSTEMGraphics system consists of four subsystems:a. Geometry engine subsystemb. Scan conversion subsystemc. Raster subsystemd. Display subsystem


RASTER SUBSYSTEMThe raster subsystem will have usually 24 bit planes. This will provide eight bit planes foreach primary color (RGB) so that (28) shades of a single color can thus obtain.Since the different colors are obtained by the three primary colors a total of (28)3colorsare available on the screen.In a typical raster engine five 256K X 4D RAM provide 4 bits of Z-depth. The rasterinformation is stored in the frame buffer. Twenty 64 K X 4 video RAM provide 4 bits foreach pixel of 1280 X 1024 resolution. Entry level systems will have 12 bit planes and highend systems will have 32 bit planes for the frame buffer. These provide the color anddepth for the images.


INTERACTIVE DISPLAY DEVICES

The display devices be can classified intotwo groups:i. Display devices based on CRT principleii. Flat screensMost interactive CAD systems use CRT based graphic monitors. CRT is a glass enclosedtube in which a finely focused electron beam is deflected to a phosphor coated screen. Thescreen then glows to produce a visible trace when excited by impinging electrons


DISPLAY DEVICES BASED ON CRTThe position of the visible trace on the CRT screen is controlled by a focusing systemand a set of horizontal and vertical deflection plates as shown in Fig. 4.12.94 CAD/CAM/CIMIn a color CRT, there are three electron guns, one each for red, green and blue. Thephosphor dots for red, green and blue are arranged in a triangular pattern. The individualbeams intersect at a shadow mask which directs a red beam to a red phosphor dot and so on.


RASTER SCAN TECHNIQUE

A raster CRT graphics device can be considered a matrix of discrete cells each of whichcan be made bright. Thus it is basically a point plotting device. If a line is to be drawn, itcan be approximated by a series of dots close to the path of the line.

Figure 4.13 illustrates this concept.


• Since the raster CRT is an analog device, it requires an electrical voltage and the digital data of the frame buffer has to be converted to an analog voltage through a digital to analog converter (DAC).

•This is schematically shown in Fig. 4.14.


• The color graphics monitors are usually referred to as RGB monitors since the different colors are obtained by mixing three primary colors, Red (R), Green (G), and Blue (B). • A simple color frame buffer can be implemented with three bit planes, one for each primary color.


• Each bit plane drives as individual color given for each of the three primary colors.

•This arrangement can lead to eight colors as given in the Table 4.3.


INPUT DEVICES

• KEYBOARDA• TOUCH SCREENS• JOYSTICKS• TRACK BALLS• MOUSE• DIGITIZER

OUTPUT DEVICES (also known as hardcopy devices)

• PLOTTERS• PRINTERS


Here are some different storage devices: Pen DriveCDDVDBlu-Ray disk Hard diskFloppy diskUSB DevicesMemory CardMultimedia CardRAMROMTape DriveCloud storageFlash memory


TRANSFORMATION IN GRAPHICS

Geometric transformations provide a means by which an image can be enlarged in size, or reduced, rotated, or moved.

These changes are brought about by changing the co-ordinates of the picture to a new set of values depending upon the requirements.


2-D TRANSFORMATIONS

In computer graphics, drawings are created by a series of primitives which are represented by the co-ordinates of their end points.

Certain changes in these drawings can be made by performing some mathematical operations on these co-ordinates.

The basic transformations are 1. Scaling2. translation 3. rotation.1. SCALING•Changing the dimensions of window and view port, it is possible to alter the size of drawings. In general, this can be done by multiplying the co-ordinates of the drawing by an enlargement or reduction factor called scaling factor, and the operation is called scaling.






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Www.engineersfox.com. Computer-aided design (CAD) is the use of computer systems to assist in the creation, modification, analysis, or optimization