ERT 243/3Computer Aided Design

For Biosystem Engineering

(CAD)Prepared By:

Siti Kamariah Md Sa’atEmail: sitikamariah@unimap.edu.my

Phone:012-7549710

Learning Outcomes

APPLY geometric construction techniques to create engineering drawings using CAD.

CREATE completes 2-D and 3-D drawings pertaining to geometric transformations, projections and multiple views.

CREATE curve, surfaces and geometric models

Assessment and Grading

PROJECT/ASSIGNMENT - 40%TEST 1 - 10%TEST 2 - 10%FINAL TEST - 40%

Introduction

Engineering drawingComputer Aided Design (CAD)

DefinitionDesign ProcessContribution CAD to DesignHistoryDesign FormatSoftwareAdvantageCapabilityLimitationBasic information include in drawing

An engineering drawing, a type of technical drawing, is created within the technical drawing discipline, and used to fully and clearly define requirements for engineered items.

What is engineering drawing?

Why Engineering Drawing?

The main purpose of engineering drawings is to communicate to other engineers, machinists, etc.

A formal and precise way of information about the shape, size, features and precision of physical objects.

Drawing is the universal language of engineering.A picture is worth a thousand

words

Why Engineering Drawing?

Giving all of the information needed to make the product and being accurate in that information is the main goal. 

Engineers are very picky about their drawings and must pay attention to detail.

What is Computer Aided Design (CAD) ?

Also known as Computer-aided drafting and design (CADD)

Describe the use of computer program to create design and engineering applications.

The computer process of making engineering drawings and technical documents more closely related to drafting.

Computer Aided Design

Computer software

Geometric Modelling

CAD

Tools in design

process

The integration of computer software and geometric model to serve the design process

Design Process Problem definition: design starts with problems

Design specification: eg. Ergonomic (one person handling), load etc

Literature work: search internally and externally (patent, field study etc)

Concept development: Development of the concept

Final concept selection: Select the final concept to develop

Detail design: Detailing the design, DFA can be applied here

Prototyping: Physical model or virtual object

Documentation: Engineering drawing and design report

Contribution of CAD in design Conceptualization

Geometric modeling, manipulation and visualization

Analysis Analysis package, FEA, optimization, customized

program

Prototyping Modeling, assemblies, animation

Communication Engineering drawing, documentation

History

CAD had its origins in three separate sources

The first source of CAD resulted from attempts to automate the drafting process. These developments were pioneered by the General Motors Research Laboratories in the early 1960s.

History

The second source of CAD was in the testing of designs by simulation. The use of computer modeling to test products was pioneered by high-tech industries like aerospace and semiconductors.

History

The third source of CAD development resulted from efforts to facilitate the flow from the design process to the manufacturing process using numerical control (NC) technologies, which enjoyed widespread use in many applications by the mid-1960s.

History

1962: SKETCHPAD system developed by Ivan Sutherland, MIT (2D graphic). For the first time, designer can interact with the computer graphically, before computer used for numerical analysis

1963: modeled in 3D by T.E JohnsonEarly application: car and aerospace companies

1970s: CAD spread widely in other sectors; film, animation, typographic etc

Evolution of CAD

Computer graphics

Computer aided drawing and drafting

Computer aided design

Design Formats

2-D Drawings Two-dimensional Having length and width/height

dimensions View of object appear in flat form Often dimensioned and contain notes and

text describe features and details of the part, map or plan.

Identical to drawing created to manual drafting technique.

Design Formats

3-D Solid Models Describe both the interior and exterior

of a part Constructed differently depending on

the software Some software allow you to produce

basic solid model using tools including solid primitive.

3D Geometric Primitives

PointLine SegmentPolygonPolyhedronCurved SurfaceSolid ObjectEtc.

CAD Software Product

Autodesk, Inc AutoCAD Autodesk Civil 3-D Autodesk Architectural Desktop

SolidWorks Corporation SolidWorks 3-D Design Software

Graphisoft ArchiCAD Design/Building Series

Advantages of CAD

Better work rather than traditional drafting methods that use rulers, squares, and compasses. For example, designs can be altered without erasing and redrawing.

CAD systems also offer “zoom” features whereby a designer can magnify certain elements of a model to facilitate inspection.

Computer models are typically three dimensional and can be rotated on any axis, enabling the designer to gain a fuller sense of the object.

CAD systems also lend themselves to modeling cutaway drawings, in which the internal shape of a part is revealed.

Advantages of CADD

1. Increased accuracy

3. Easy to revise

2. Increased drawing speed

4. Availability of drawing libraries

Draftingstage

1. Built-in several analysis tools

2. Better presentation (Easy to visualize) - Pan, rotate, animate, shade, texture

Designstage

CADD Capability

1. Draw

3. Dimension

2. Modify

4. Object snap

5. Layer concept

Limitation of CADD(within scope of drawing creation)

Good engineering drawings must have the following

characteristics.

Parts or product information is completely given.

Information is clearly presented .

Information can be used in manufacturing of part.

Always remind yourself that

“Good drawing cannot be created by using CADD

software

alone without understanding the drawing concepts.”

Apply a proper line weight and style.

Select a necessary view.

Decide the appropriate places of dimensions.

Select an appropriate section techniques (if necessary)

Limitation of CADD(within scope of drawing creation)

To create a good engineering drawings YOU MUST

do the following tasks yourself.

Limitation of CADD(within scope of drawing interpretation)

Because they are frequently used technical document.

Therefore,YOU MUST prepare yourself for interpreting

(or visualizing) them when you become ENGINEER.

No CADD software can create a pictorial view from

an orthographic multiview.

Projected Views: Show as many sides as needed for completeness.

Cross Sections: A view that is good for showing interior features.

Table: Lower right corner, with material information, part name, designer etc

Dimension: These are the most important and most complicated part of the drawing. There is more to it than just the numerical values!

Dimensions tell how far it is from one point on an object to another point.  The most basic type is called a Linear Dimension because it gives the straight-line distance from one point to another.  There are also Radial, Diameter and Angular Dimensions.

Dimensions have four basic components: Dimension Text Dimension Line and Arrows Extension Lines Gap

More basic information

Standard CodeLinesScaling

ISO International Standards Organization

Standard Code

ANSI American National Standard InstituteUSA

JIS Japanese Industrial StandardJapan

BS British StandardUK

AS Australian StandardAustralia

Deutsches Institut für NormungDINGermany

Country Code Full name

มอก. สำ��นั�กง�นัม�ตรฐ�นัผลิ�ตภั�ณฑ์�อ�ตสำ�หกรรมThailand

Basic Line Types

Types of Lines AppearanceName according

to application

Continuous thick line Visible line

Continuous thin line Dimension line

Extension line

Leader line

Dash thick line Hidden line

Chain thin line Center line

Visible linesVisible lines represent features that can be seen in the

current view

Meaning of Lines

Hidden linesHidden lines represent features that can not be seen in

the current view

Center lineCenter line represents symmetry, path of motion, centers

of circles, axis of axisymmetrical parts

Dimension and Extension linesDimension and Extension lines indicate the sizes and

location of features on a drawing

Example : Line conventions in engineering drawing

Line Convention

Precedence of coincide lines.

Hidden line drawing.

Center line drawing.

Precedence of Line

Visibleline

Visibleline

Order ofimportance

Hiddenline

Hiddenline

Centerline

Centerline

Hidden Line Practice

Hidden line should join a visible line, except itextended from the visible line.

Correct

No !

Join

Leavespace

Correct No !

Hidden line should join a visible line, except itextended from the visible line.

Leavespace

Leavespace

Hidden Line Practice

Hidden line should intersect to form L and Tcorners.

Correct

No !

L T

Hidden Line Practice

Hidden arcs should start on a center line.

Hidden Line Practice

Centre Line Practice

In circular view, short dash should cross at the

intersections of center line.

For small hole, center line is presented as thin

continuous line.

Center line should not extend between views.

Leave space Leave space

Leave the gap when centerline forms a

continuation with a visible or hidden line

Leavespace

Leavespace

Leavespace

Leavespace

Center line should always start and end with

long dash.

Centre Line Practice

Scaling is used to depict objects on paper that are either larger or smaller than the paper. If the object is larger than the paper, then the views of

the object are scaled Down If the object is smaller than the paper, then the views of

the object are scaled Up If the object fits on the paper, then the views are

depicted at Full scale  (1:1)

Scaling

Drawing Sheet

•Trimmed paper of a size A0 ~ A4.

•Standard sheet size (JIS)

A4 210 x 297

A3 297 x 420

A2 420 x 594

A1 594 x 841

A0 841 x 1189

A4

A3

A2

A1

A0

(Dimensions in millimeters)

Drawing space Drawingspace

Title block

d

d

c

c

cBorder lines

1. Type X (A0~A4) 2. Type Y (A4 only)

Orientation of drawing sheet

Title block

Sheet size c (mm) d (mm) A4 10 25 A3 10 25 A2 10 25 A1 20 25 A0 20 25

The end…