CE En 112 Engineering Drawing with CAD Application

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CE En 112 Engineering Drawing with CAD Application - PowerPoint PPT Presentation

CE En 112 Engineering Drawing with CAD Application. Chapter 2: Sketching and Text (Lecture B) Multiview Drawings. Lecture Outline. Objectives Projection methods (2.4, p.85) Multiview projections (2.4.4, p.93) Multiview sketches (2.6, p.99) Visualization (in the PP file only)

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CE En 112 Engineering Drawing with CAD Application

Chapter 2: Sketching and Text (Lecture B)

Multiview Drawings

Lecture Outline
• Objectives
• Projection methods (2.4, p.85)
• Multiview projections (2.4.4, p.93)
• Multiview sketches (2.6, p.99)
• Visualization (in the PP file only)
• Multiview representations (in the PP file only)
• ANSI standards (in the PP file only)
• Next class
Objectives
• Learn the rules for reducing a 3D object onto a 2D multiview drawing
• Learn some hints for visualizing a 3D object from a 2D multiview drawing
• Covers material in Chapter 2, primarily Sections 2.4, 2.5, and 2.6 as well asmaterial not in text
Projection Methods (2.4)

Locate multiview projections in the taxonomy of projections:

Projection  Parallel Projections  Orthographic Projections  Multiview Projections

Object

Projection plane

Line of sight

Multiview Projections (2.4.4)

Multiview is classified as parallel projection because lines of sight used to view the object are parallel

Multiview Projections (con’t)

Multiview projection is an orthographic projection for which the object is behind the plane of projection and oriented such that only two of its dimensions are shown

Multiview Projections (con’t)

Object suspended in a glass box, producing the six principal views

Multiview Projections (con’t)
• Glass box video:
• http://highered.mcgraw-hill.com/sites/0072864583/student_view0/chapter5/animations.html#

Multiview Projections (con’t)

Multiview Projections (con’t)
• Choosing the views and orientation for a multiview object:
• Determine the best position of the object
• Try to make the surfaces of major features either perpendicular or parallel to the projection planes
• Define the front view (the front view should show the object in its natural or assembled state)
• Determine the minimum number of views needed to completely describe the object so it can be produced
• Once the front view is selected, determine which other views will have the fewest number of hidden lines
Multiview Projections (con’t)

View Orientation

Good orientation

Multiview Projections (con’t)

Most Descriptive Views

(More visible lines better)

Multiview Sketches (2.6)
• Multiview drawings can have from one to three or more views of an object (rarely are more than three views necessary)
• One-view sketches: include simple objects such as a sphere, cylinder, or cube. Other applications include a thin gasket or printed circuit board (no depth)
• Two-view sketches: include cylindrical, conical, and pyramidal shapes
• Three-view sketches: used when an object is more complex and requires three views to communicate all aspects of the drawing (width, depth, and height)
Multiview Sketches (con’t)

One-View Sketches

Two-View Sketches

Creating a Three-view sketch:

Step 1: Block in the front, top, and right side views. Sketch the front view first using construction lines to project dimensions

Step 2: Lightly block the major features in views

Step 3: Use construction lines to project the location and size of features between views

Step 4: Finish adding the final lines

Multiview Sketches (con’t)

Normal plane

Oblique plane

Inclined plane

Visualization of Edges and Planes

Fundamental Views of Planes

Oblique line

Normal line (true-length)

Inclined line

Visualization (con’t)

Fundamental Views of Edges

Visualization (con’t)

Normal, Inclined, or Oblique?

A: parallel to frontal plane

B: parallel to horizontal plane

C: parallel to profile plane

D: inclined – on edge in front view

E: oblique – neither parallel or on edge in any plan or view

Multiview Representations
• Practice makes perfect, without it, you will never learn this art of visualizing 3D objects from 2D multiview drawings
• Some items to consider in multiview representation and visualization:
• Projection studies
• Physical model construction
• Missing lines
• Vertex labeling
• Analysis of solids
• Analysis of surfaces
Multiview Representations (con’t)

Possible Solutions

Multiview Representations (con’t)

There are several examples of multiview representations in this and other texts. The best method to learn the art of multiview representation of 3D objects is to draw by yourself, with tools or freehand, the objects in the Problems section of the text. We do not have time to cover all that are presented in the chapter. This section presents some examples of multiview representation.

Multiview Representations (con’t)

This length has to be measured. And the curved line in top view must be drawn first. (The bottom plane is flat.)

ANSI Standards for Multiview Drawings

Partial Profile Views to Describe an Object and Eliminate Hidden Lines

Partial View used on a Symmetrical Object

ANSI Standards (con’t)

Too “busy”

Revolution Conventions used to Simplify the Representation of Ribs and Webs

ANSI Standards (con’t)

Removed View

Make the drawings easy to understand!

Revolution Applications

Examples