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# Orthographic Projection - PowerPoint PPT Presentation

Orthographic Projection. Lecture 3. Today’s Activities . Today More On Multi-view Orthographic Drawings BTG Chap 4 Orthographic Projection Teamwork Workshop Tomorrow Learn how to do isometric drawings First AutoCAD Lesson. Projection Methods (BTG pg 123). Perspective projections

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### Orthographic Projection

Lecture 3

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• Today

• More On Multi-view Orthographic Drawings

• BTG Chap 4

• Orthographic Projection

• Teamwork Workshop

• Tomorrow

• Learn how to do isometric drawings

• First AutoCAD Lesson

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• Perspective projections

• Linear 1, 2, or 3 Vanishing points

• Aerial

• Parallel projections

• Oblique projection: cavalier, cabinet, or general

• Orthographic projection

• Axonometric

• Isometric, dimetric, or trimetric

• Multi-view

• First-angle or third-angle

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From Fundamentals of Graphic Communications by Bertoline, McGraw-Hill

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First-angle Projection

First Angle Vs. Third Angle

From Fundamentals of Graphic Communications by Bertoline, McGraw-Hill

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Review - Why Multi-view?Give 3 reasons

• Most accurate description of 3-D objects for engineering, manufacturing, and construction

• Dimensions of features are presented in true size in one or more views

• Easy transition to 3-D database and computer modeling

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• Every point or feature must be aligned on a parallel projector in any adjacent view.

• Distances between any two points in a related view must be equal.

• Features are true length or true size when the lines of sight are perpendicular to the feature.

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• Features are foreshortened when lines of sight are not perpendicular to the feature.

• Areas that are the same feature will always be similar in configuration from one view to the next, except when viewed on the edge. - Example: Triangular surface always has three sides in all views

• Parallel features will always appear parallel in all views.

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• Surfaces that are parallel to the lines of sight will appear as lines or edge views.

• No two contiguous (adjacent) areas can lie in the same plane.

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• Identify the major features and overall dimensions of the object

• Do not use your scale as a pencil guide when sketching by hand

• Start by drawing bounding boxes with light construction lines.

• Keep views aligned while sketching

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• Only measure along the primary axes fi you are working from a pictorial.

• Map inclined and oblique faces among all three views

• Follow the precedence of lines

• Darken all visible, hidden, and center lines

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• Hidden Line – used to represent features that cannot be seen in the current view

• Centerlines – used to represent symmetry and to mark the center of circles and the axes of cylinders, and the axes of symmetrical parts, such as cylinders and bolts

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VISIBLE LINES takes precedence over hidden and center lines

HIDDEN LINES take precedence over center lines

CENTER LINE does not have precedence

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Depth

Top View

Right SideView

Front View

Height

And… Set up Conventional Three-View

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Steps in Creating the Three-View SketchCompleted Sketch

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• Dwg 5 – A11

• Orthographic Sketches from an Isometric

• Due tomorrow morning

• Dwg 6 – Team Agreement

• Due tomorrow morning

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