CAD VS MANUAL APPLICATION CAD VS MANUAL APPLICATION Before starting your engineering drawing you should plan how you are going to make best use of the space It is important to think about the number o[.]
CAD VS MANUAL APPLICATION One of the best ways to communicate an ideas is through some form of picture or drawing Before starting your engineering drawing you should plan how you are going to make best use of the space It is important to think about the number of views your drawing will have and how much space you will use of the paper ISOMETRIC DRAWING The representation of the object in figure is called an isometric drawing In an isometric drawing, the object's vertical lines are drawn vertically, and the horizontal lines in the width and depth planes are shown at 30 degrees to the horizontal ORTHOGRAPIC PROJECTION •The aim of an engineering drawing is to convey all the necessary information of how to make the part to the manufacturing department • For most parts, the information cannot be conveyed in a single view • Rather than using several sheets of paper with different views of the part, several views can be combined on a single drawing using one of the two available projection systems, - first angle, - third angle FIRST ANGLE PROJECTION The diagram below demonstrates how the projection systems work • With first angle projection, the view you are looking at is projected through to the other side of the object • If we are drawing the three visible sides of the object illustrated in first angle projection, we are drawing the views projected on the other side of the object and not three nearest views THIRD ANGLE PROJECTION • Using third angle projection, the view you are looking at is displayed at the same side • If we are drawing the three nearest faces of this object, the top and the two nearest views are the ones we would draw with the top view appearing above the side view DIMENSIONING • The purpose of dimensioning is to provide a clear and complete description of an object A complete set of dimensions will permit only one interpretation needed to construct the part Dimensioning should follow these guidelines – Accuracy: correct values must be given – Clearness: dimensions must be placed in appropriate positions – Completeness: nothing must be left out, and nothing duplicated – Readability: the appropriate line quality must be used for legibility DIMENSIONING • We have "dimensioned" the object in the isometric drawing • As a general guideline to dimensioning, try to think that you would make an object and dimension it in the most useful way • Put in exactly as many dimensions as are necessary for the craftsperson to make it -no more, no less • Do not put in redundant dimensions • If "tolerances" or accuracy levels have been included, the redundant dimensions often lead to conflicts when the tolerance allowances can be added in different ways DIMENSIONING • Detailed dimensions required for manufacture are excluded from assembly drawings But overall dimensions of the assembled object are usually indicated • If the spatial relationship between parts if important for the product to function correctly then these should also be indicated on the drawing • For example indicating the maximum and minimum clearance between two parts Definitions and Dimensions The dimension line is a thin line, broken in the middle to allow the placement of the dimension value, with arrowheads at each end Where To Put Dimensions The dimensions should be placed on the face that describes the feature most clearly SECTIONING Cross-Sectional Views Sectioning Objects with Holes, Ribs, Etc Half-Sections ASSEMBLY DRAWINGS • The assembly of these parts is shown in an assembly drawing also known as a general arrangement • It corresponds closely to what you actually see when viewing the object from a particular angle Parts list • Each part is given a unique number, indicated on the drawing by a circle with the number in it and a leader line pointing to the part • The leader line terminates in an arrow if the line touches the edge of the component, or in a circle if the line terminates inside the part Industrial Scenario • Global • World class organisation • Labour problem • Dynamic, highly adaptive • Shorter product life cycle • Emphasis on quality • Rapid technology advances Changing Environment • CHANGES • CORPORATE STRATEGY • Business Patterns • Technology • Methods • Standards • Data processing • • • • • Business Automation Integration Information Resources ENTERPRISE COMPETITION INNOVATION FAST COST QUALITY Industry Trend for the Product Development Process • • • • Less time to design, develop and prove out Improved quality Less costs, waste and warranty returns One Main Focus: Get the product released closer to market demand Longer to market means less likely product will meet customer wants Comparison of Product Development Cycle Typical of Automotive Industry BEFORE 37 – 48 months NOW 16 – 24 months What is CAD • CAD – Computer Aided Design • CAD now involved concept to production • A generic term for all aspects of design using computer software tools • Usually covers geometry creation, manipulation and the production of drawings CAD – Description • The use of computer systems to assist in the creation, modification, analysis or optimisation of a design • The computer system consists of the hardware and software to perform the specialised design functions required by the particular user • Hardware – computer, one or more graphics display terminals, keyboards and other peripheral equipment • Software – computer programs to implement computer graphics on the system plus application programs to facilitate the engineering functions of the user DEVELOPMENT IN CAD Complexity Functionality Internet Web-enabled Collaborative NT, Linux Solid model Low-cost Desktop Pro-engineer More functions Complex 3D Kernel modeller AutoCAD PC CAD Unix workstation Mini computer Turnkey CAD Drafting 32 bit midi computer More functionality Expensive Solid modelling research Large computer Dedicated system Limited company Very expensive R & D at universities 1950 1960 1970 1980 1990 2000 ... Typical of Automotive Industry BEFORE 37 – 48 months NOW 16 – 24 months What is CAD • CAD – Computer Aided Design • CAD now involved concept to production • A generic term for all aspects of design... Low-cost Desktop Pro-engineer More functions Complex 3D Kernel modeller AutoCAD PC CAD Unix workstation Mini computer Turnkey CAD Drafting 32 bit midi computer More functionality Expensive Solid modelling... programs to implement computer graphics on the system plus application programs to facilitate the engineering functions of the user DEVELOPMENT IN CAD Complexity Functionality Internet Web-enabled Collaborative