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Geometric Modeling Techniques

chapter 6

SALIENT (PRINCIPAL) FEATURES OF SOLID MODELING

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Salient Features of Solid Modeling

• Feature based design

• Modeling tools

• Characteristics of solid modeling packages

Feature based design

Sk t h b dSketch based

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Feature based design

Pick and place

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Modeling tools

• Sketching (2D)

• Creating part

• Assembly

• Documenting design

Characteristics of SM package

• Parametric design

• Relations and relationships

• Behaviour modeling

– Smart models

– Engineering objective based design

O t ibl i t– Open extensible environment

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Relationship

Relationship

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FEATURES OF DRAFTING PACKAGES

Features of Drafting Packages

• Drawing utilities • Dimensioninga g u es

• Entity drawing

• Edit commands

• Standard parts

• Display

e s o g

• Plotting

• Configuration

• Customization

• Drawing Interchange

• Cross hatching

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DRAWING UTILITIES

Drawing Utilities

• Screen size

S li

• Specifying points

Li t t t f t• Scaling

• Grid

• Snap

• Units

• Line type, text fonts, and shapes

• Layers

• Saving a drawing

• File utilities

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Layer

ENTITIES

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Entities

Tugas: baca sub‐bab di bawah ini

• Edit commands

• Block and symbols

• Display

• Cross hatching and pattern filling

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DIMENSIONING

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3D DRAWINGS

3D Drawings

• Extrusion (linear sweep)

• Revolution

• Using UCS (user coordinate system)

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Tugas: belajar sub‐bab di bawah ini

• Plotting a drawing

• Configuring the drafting software

• Customization

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DRAWING INTERCHANGE FILE

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DRAWING OFFICE MANAGEMENT

Drawing office management

• Creation of parts list

Bill f t i l (BOM)

• Project costing

P d t i ti• Bill of material (BOM)

• Searching for similar design

• Design changes

• Replacing faulty 

• Product variations

• Web enabled softwares

• Integrated drafting, design, and documentations

components

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SURFACE MODELING

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CURVE AND SURFACE REPRESENTATIONS

Generic Form

0f 0,, zyxf

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Parametric form

Properties of parametric reps

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CURVE & SURFACE DESIGN

Design of curve shapes

• Mathematical representation of shape

• Minimum computation

• Ability to generate a CNC program

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PROBLEMS WITH SPLINE

INTERPOLATION

Criteria of curve modeling

• Axis independence

• Global and local control

• Smoothness of curves

• Versatility

• Continuity between adjoining segments of curves

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CUBIC SPLINES – POLYNOMIAL BASIS

Hitung persamaan curva 3D:1 X(0) i t l i l1.X(0) – interpolasi awal2.X(1) – interpolasi akhir3.X’(0) – singgung awal4.X’(1) – singgung akhir

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LIHAT HALAMAN 156

page 159

BEZIER CURVES – BERNSTEIN BASIS