03 [Wk02L1] Eng design & eng geometry.ppt

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03

MEMB113 ENGINEERING

GRAPHICS & CAE

ENGINEERING DESIGN

ENGINEERING GEOMETRY



MEMB113 | Dept. of Mechanical Engineering | UNITEN | 200503 ENGINEERING DESIGN | ENGINEERING GEOMETRY

Contents

• Engineering design

• Engineering geometry

• How to draw?

– Examples of previous exercises



Engineering Design




Design

• Design is the process of conceiving or inventing

ideas mentally and communicating those ideas

to others in a form that is easily understood.

• Normally using graphical way.

• Generally, design is used for two primary

purposes:

– Personal expression (usually art) – Product/process development




Category of design

DESIGN

Product/Process

Development

(Technical)

Personal Expression

(Artistic)

Aesthetic

(Industrial design)

Functional

(Engineering Design)

Engineering

Design Cycle

Product Process




Engineering design

• Engineering drawing in design process

to see the problem

& possible solutionsVisualise

Sketches

Geometric model

Detail drawings

3D model

to record initial ideas

created from sketches

used for analysis

to record the precise data

for production process

Visualisation is the

ability to mentally

picture things that do

not exist

Communicat ion -

the design solution

should be

communicated to

others without

ambiguity

Documentat ion -

permanent record of

the solution



Engineering

Geometry




Overview

• Geometry provides the building blocks for theengineering design process.

• Engineering geometry is the basic geometric

elements and forms used in engineering design.• Coordinate system – cartesian coordinate system

– polar coordinate system

Cartesian coordinate system Polar coordinate system

MEMB113 | MANUAL DRAWING | CHAPTER 3




Overview

• Absolute coordinate & Relative coordinate

• Right hand rule

– to determine positive direction of axis

AbsoluteRelative

Right hand rule




Geometric elements

• Can be categorised as points, lines, surfaces,solids.

• Points, lines, circles and arcs are basic 2Dgeometric primitives.





Geometric elements

– Point - theoretical location that has neither

width, height, nor depth. It describe an exact

location in space. Represented as a small

cross.

– Line - has length and direction, but not

thickness. May be straight or curve or both.


|




Geometric elements

– Circle - is a single-curved-surface, all points of

which are equidistant from one point, the

center


03 ENGINEERING DESIGN | ENGINEERING GEOMETRY




Geometric elements

Major components of a circle


03 ENGINEERING DESIGN | ENGINEERING GEOMETRY




Tangent

• A line is tangent to acircle if it touches thecircle at one and only onepoint.

• At exact point oftangency, a radius makesa right angle to thetangent line.

• Two curves are tangentto each other if they touchin one and only place.

Tangent point

between a

straight line & a

circle

Tangent point

between two

circles (curves)



How to draw?

MEMB113 | D t f M h i l E i i | UNITEN | 200503 ENGINEERING DESIGN | ENGINEERING GEOMETRY




How to draw?

• All drawing consist of the combination of

basic geometric elements.

• Some of the common elements: – Straight lines

– Circles

– Arcs – Freeform curves

MEMB113 | D t f M h i l E gi i g | UNITEN | 200503 ENGINEERING DESIGN | ENGINEERING GEOMETRY




How to draw?

• E.g. simple object as shown

• Inspect the overall size of theobject – compare to the availabledrawing space to decide on thesuitable scale

• Observe the feature

• Start drawing – Draw circle & arc first (if any)

– Draw centre lines before that

– Make sure of using correct pencilor line thickness

– Draw straight lines – Add in other things e.g.dimensions, etc.

• Be careful of ‘blending’ andcleanliness of the drawing

• Make your drawing sharp andsolid

MEMB113 | Dept of Mechanical Engineering | UNITEN | 200503 ENGINEERING DESIGN | ENGINEERING GEOMETRY




Points to remember

• Overall shape & feature

• Line quality (thickness,consistency, etc.)

• Size & scale• Dimension (if available)

• Drawing quality(cleanliness, etc.)

• Projection (if any)

• Other info





• Line quality – good

• Good solid object line

• line thickness – good

use of thick & thin

• construction of arcneed to be improved

• blending can be further

improved

Drawing examples





• Line thickness not

consistent

• Poor blending

• construction lines –

too thick, need to erase

• circle construction –

poor

• dimensioning – poor

• scale not written

Drawing examples





• Object lines – too thin

• Object lines & centre

lines – same thickness

• Dimensioning – not

follow standard

Drawing examples





• Line quality – good

• Good solid object line

• line thickness – good

use of thick & thin

• construction of arc

need to be improved

• blending can be further

improved

Drawing examples





• Object shape is wrong!

•Line thickness not

consistent

• Poor blending

• construction lines – too

thick, need to erase

• circle construction –

poor

• dimensioning – poor

• scale not written

Drawing examples




| p g g | |03 ENGINEERING DESIGN | ENGINEERING GEOMETRY

• Line quality –

acceptable but should

be darker

• blending between

straight line & arc needimprovement

• good lettering

• missing scale

Drawing examples



End of chapter [03]

References:

- Engineering Drawing, A.W. Boundy, McGraw-Hill,2000

- Fundamentals of Graphics Communication 3rdEdition, Gary Bertoline & Eric Weibe, McGraw-Hill

Documents

03 [Wk02L1] Eng design & eng geometry.ppt