Orthographic Projections GMED Unit 1

Lecture Outline Objectives Projection methods (2.4) Multiview projections (2.4.4) Multiview sketches (2.6) Visualization Multiview representations ANSI standards 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 as material not in text

Projection Methods (2.4) Locate multiview projections in the taxonomy of projections: Projection  Parallel Projections  Orthographic Projections  Multiview Projections

Multiview Projections (2.4.4) Line of sight Projection plane Object 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 Six Principal Views See also Figure 2.35 in text

US (ANSI 3rd-angle projection) vs. ISO (1st-angle projection) Multiview Projections (con’t) US (ANSI 3rd-angle projection) vs. ISO (1st-angle projection)

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 Bad orientation Good orientation

Multiview Projections (con’t) Most Descriptive Views

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

Multiview Sketches (con’t) 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

Visualization of Edges and Planes Normal plane Oblique plane Inclined plane Fundamental Views of Planes

Visualization (con’t) Fundamental Views of Edges Oblique line Inclined line Normal line (true-length)

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 Adjacent labeling Missing lines Vertex labeling Analysis of solids Analysis of surfaces

Multiview Representations (con’t) Adjacent Areas 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)

Multiview (con’t)

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

Next Class Worksheet - changing isometric drawings to orthographic drawings. Copy of the worksheet can be found at http://gmed.wetpaint .com