Week 3_MIET2093_Arc and 3D drawing

Prévia do material em texto

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MIET2012 
1 
Lecture 3: Arc, Curve & 3D modelling 
AERO 2430 
AEROSPACE DESIGN 1 
 
by: 
Dr. Toh Yen Pang 
tohyen.pang@rmit.edu.au 
9925 6128 
B251.3.22 
School of Aerospace, Mechanical & Manufacturing Engineering 2 RMIT University©2015 
Weekly schedule 
Teaching 
Week 
Lecture Topics Tutorial topics Assessments/Tasks 
Week 1 
Introduction to 
Engineering 
Design & 
Graphics 
Introduction to 
Enovia and 
Getting Started 
with CATIA 
 
Week 2 
Sketches: 
Freehand and 2D 
sketches 
Introduction to 
Sketcher 
Workbench 
 
Week 3 
Drawing: 2D & 
3D solid 
modeling 
Part Design: Basic 
Features 
 
Week 4 Projections and 
Views 
Part Design: 
Dress up Features 
Quiz 1 
Group Project 
(Max. 5 member 
team) 
!
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Problem solving steps 
1. Calculate the required space. 
2. Layout the drawing steps. 
3. Match the construction techniques to each drawing step. 
4. Start drawing. 
Always use a construction line if the information to draw 
a line or a curve is incomplete. 
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Scales 
•  Before you start any drawing you first decide how large the 
drawings have to be.
•  The object may be much too large for the paper or much too 
small to be drawn clearly. 
•  There are drawing aids called ‘scales’ which are designed to 
help the draughts person to quickly enlarge or reduce the 
drawing measurements 
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Draw the sketch of the model 
shown in the figure and 
include all the necessary. 
Example 
Quiz 1 
 
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•  Construction 2D Arc and Curve 
•  Understanding 3D space 
•  Axes, planes and faces 
•  Solid 3D modeling 
•  Understand constraint-based and feature-based 3-D modeling 
Objectives 
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2-D geometry 
1. Straight line (Horizontal, vertical and Inclined) 
2. Arc, circle and curve 
A two-dimensional geometry is always composed of 
Example 
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Definition (1/2) 
Tangent circles – coplanar circles that 
intersect in one point 
Concentric circles – coplanar 
circles that have the same center. 
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Definition (2/2) 
common internal tangent common external tangent
Common tangent – a line or segment that is tangent to two 
coplanar circles 
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Drawing a circle tangent 
to other object 
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Circle & Arc 
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3-minute discussion 
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Key Concept 
1. its center, C. 
To draw a tangent arc (of a specified radius, R), 
it is necessary to locate 
2. the start and end points 
 (or tangent points) of the arc. 
It places outside a line for a distance 
equal to a radius of an arc. 
It lies on a given line in the way 
that the line passing through this 
point and the center of an arc be 
perpendicular to a given line. 
R 
R R 
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Tangent arc to the given lines 
R 
R 
play 
Given 1. Locate the center of an arc 
Continue 
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TP.1 
TP.2 
Tangent arc to the given lines 
2. Locate the tangent points 
Replay 
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Drawing a tangent curve 
to the given curves 
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Tangent point lies on the line passes through the centers 
of each arc (or circle). 
Key Concept 
R1 
R2 
R3 
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Tangent arc to a given arcs (or circles) 
C2 C1 
C 
C1 C2 
C 
1. its center, C. 
To draw a tangent arc (of a specified radius, R), 
it is necessary to locate 
Case 1 : External Case 2 : Internal 
2. the start and end points (or tangent points) of the arc. 
R1 
R R 
R2 R1 
R-R1 R-R2 
R2 
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+ + C1 
C2 
R + R1 
R + R2 
R1 
R2 C 
External tangent arc 
R 
play 
Given 
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Practice by Yourself 
Draw the sketch of the model shown in Figure. Do not dimension 
the sketch, its dimensions are give only for your reference.
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+ + C1 C2 
R – R2 
Internal tangent arc (Type 1) 
R – R1 
R1 
R2 
C 
R 
play 
Given 
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Practice by Yourself 
Draw the sketch of the model shown in Figure. Do not dimension 
the sketch, its dimensions are give only for your reference.
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R + R2 
R – R1 
C 
Internal tangent arc (Type 2) 
+ + C1 
C2 
R1 
R2 
play 
R 
Given 
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Practice by Yourself 
Draw the sketch of the model shown in Figure. Do not dimension 
the sketch, its dimensions are give only for your reference.
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Practice by Yourself 
Draw the sketch of the model shown in Figure. Do not dimension 
the sketch, its dimensions are give only for your reference.
MIET2012 
3D Geometric 
Forms 
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Gindis, Elliot. Up and Running with AutoCAD 2012 : 2D and 3D Drawing and Modeling (3rd Edition). Saint Louis, MO, USA: Academic Press, 2012. 
What is 3D Drawing? 
It is the ability to give depth to objects, or to expand 
them into the “third dimension” from a flat plane. 
We live in a 3D world and everything has not just a 
length and width but also a depth (or height). 
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The advantages of 3D modeling 
•  Productivity, with the flexibility to modify design at different levels
•  The prototyping attribute of 3D models
•  3D models can be used as marketing tools
•  Enhanced competitiveness
•  Design communication
•  Enhanced visual attribute
•  Construction stage foresight15/03/15 
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“Engineering drawing” or “blueprint” uses lines to 
represent the features of an object. 
Features of an object are surface (include plane) and 
edge. Face 
Edge 
3D Geometry: Shape Description 
Shape description of an object refers to the positions 
of its component geometric elements (e.g., vertices, 
edges, faces) in space . 
Vertice 
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3D Geometry: Coordinate Space (1/2) 
In order to locate points, lines, planes, or other geometric 
forms, their positions must first be referenced to some 
known position, called a reference point or origin of 
measurement. 
The Cartesian coordinate system, introduced by Rene 
Descartes, is commonly used 
The right-hand rule is used to 
determine the positive direction of 
the axes. 
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3D Geometry: Coordinate Space (2/2) 
A standard page layout has two axes: x and y. If these 
equate to the horizontal and vertical directions, 
respectively, then the third axis (z) extends off the screen, 
toward the viewer. 
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Axes, planes and faces 
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World coordinate 
system (origin) 
Local coordinate 
system 
Coordinate Systems 
Coordinate Systems 
0, 0, 0 
X 
Z 
Y World coordinate system 
Y 
Z 
X 
Local coordinate system 
0, 0,
 0 
Where objects are in the world Relative to 
position of object 
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Coordinate Systems 
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MIET2012 
Constraining profile for 
3D modeling 
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Topology & Geometry 
60 
40 10 
15
 3
0 
7 
Sketching Topology 
Constraints Geometry 
Profile 
• size 
• Location 
• orientation 
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Geometrical 
(Implicit) 
Dimensional 
(Explicit) 
Constraints 
Constraining Profiles 
Tangency Paralellism Perpendicularity 
Same size Coincident 
Concentric 
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Fully constrained 
Completely specifies the geometry of a profile 
Underconstrained 
One or more elements that have not been fully specified 
Constraining 
The constraints are in conflict with each other 
àundesirable 
Overconstrained 
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MIET2012 
3D Modeling: 
Solid 
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A solid model will show how the surfaces on object will appear 
3D Solid Model 
Solid model provides information on surface, area, 
volume, and weight 
Example 
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Approaches to developing a 
solid model 
Constraint-based modeling 
Feature-based modeling 
Boundary Representation (B-rep) modeling 
Parametric modeling 
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Hierarchy of 3D objects 
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Develop a Solid Model 
Constraint-based solids 
Begins with the creation of a 2-D sketch of a profile 
Constrained or detailed by adding dimensions 
3-D Objects created by revolving or extruding 
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Constraint-based solids: Extrude 
What is needed for the extrude modeling technique? 
Example 
Closed profile 
Direction 
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Constraint-based solids: Extrude 
What is needed for the extrude modeling technique? 
Example 
Closed profile 
Direction 
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Constraint-based solids: Revolve 
2 things needed 
Closed profile & Axis 
What is needed for the revolved sweep? 
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Revolve 
Draw a 2D outline of an object and revolve this outline or 
“profile” around an axis. 
Example 
If the profile is closed, the result is a solid of revolution 
If the profile is open (has gaps) or lines are used instead of 
polylines, the result is a surface of revolution 
Gindis, Elliot. Up and Running with AutoCAD 2012 : 2D and 3D Drawing and Modeling (3rd Edition). Saint Louis, MO, USA: Academic Press, 2012. 
Rotation axis 
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Feature-based solids: Sweeps (1/2) 
What is needed for the extrude modeling technique? 
Example 
Closed profile (sketch on a plane) 
Direction (path) 
A based feature is selected, successive feature is defined by 
adding or removing material to complete the design 
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Example 
Feature-based solids: Sweeps (2/2) 
1.  A based feature is selected 
2.  successive feature is defined 
3.  Additional features can be extruded in two direction 
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References: 
•  I. Stroud, Solid Modelling and CAD Systems : How to Survive a 
CAD System, Springer, 2011
•  Aouad, Ghassan; Wu, Song; Lee, Angela. Architecture Engineering 
and Construction.Florence, KY, USA: Routledge, 2011.