Geometric modeling

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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 awal
2.X(1) – interpolasi akhir
3.X’(0) – singgung awal
4.X’(1) – singgung akhir

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LIHAT HALAMAN 156
page 159
BEZIER CURVES – BERNSTEIN BASIS