axonometric projection chapter 14. 2 technical drawing 13 th edition giesecke, mitchell, spencer,...

Axonometric Projection

Chapter 14

2Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.

Objectives

• Describe the differences between multiview projection, axonometric projection, oblique projection, and perspective

• Sketch examples of an isometric cube, a dimetric cube, and a trimetric cube




Objectives (cont.)

• List the advantages of multiview projection, axonometric projection, oblique projection, and perspective

• Create an isometric drawing given a multiview drawing

• Use the isometric axes to locate drawing points




Objectives (cont.)

• Draw inclined and oblique surfaces in isometric

• Draw angles, ellipses, and irregular curves in isometric




Projection Methods




Types of Axonometric Projection• Isometric – has equal foreshortening

along each of the three axis directions• Dimetric – has equal foreshortening

along two axis directions and a different amount on the third axis

• Trimetric – has different foreshortening along all three axis directions




Types of Axonometric Projection




Isometric Projection

• The projections of the edges of a cube in isometric projection make angles of 120 degrees with each other





• Lines of an isometric drawing that are not parallel to the isometric axes are called nonisometric lines• These lines are not

equally foreshortened





• Isometric scales can be used to draw correct isometric projections• All distances are approximately 80%

of true size




Isometric Drawings

• Isometric drawings, unlike isometric projections, are drawn using the full length measurements of the actual drawing and lacks foreshortening• The isometric drawing is about 25%

larger than the isometric projection




Making an Isometric Drawing




Isometric Drawings of Inclined Surfaces




Hidden Lines and Centerlines• Hidden lines are omitted unless

they are needed to make the drawing clear

• Center lines are shown if they are needed to indicate symmetry or if they are needed for dimensioning




Angles in Isometric

• Angles project true size only when the plane containing the angle is parallel to the plane of projection

• An angle may project to appear larger or smaller than the true angle depending on its position




Irregular Objects




Curves in Isometric




Ellipses in Isometric

• If a circle lies in a plane that is not parallel to the plane of projection, the circle projects as an ellipse

• Ellipses can be constructed using offset measurements




Ellipses in Isometric

• Approximate ellipses can be constructed from arcs




Drawing Isometric Cylinders




Screw Threads in Isometric

• Parallel partial ellipses equally spaced at the symbolic thread pitch can be used to represent screw threads




Arcs in Isometric




Intersections




Spheres in Isometric




Isometric Sectioning

• Isometric sectioning is useful in drawing open or irregularly shaped objects




Isometric Dimensioning

• Isometric dimensions are similar to dimensions on multiview drawings but should match the pictorial style




Exploded Assemblies




Piping Diagrams




Dimetric Projection

• A dimetric projection is an axonometric projection of an object where two of its axes make equal angles with the plane of projection and the third axis makes either a smaller or a greater angle




Dimetric Projection




Trimetric Projection

• Trimetric projection is an axonometric projection where no two axes make equal angles with the plane of projection

• Each of the axes have different ratios of foreshortening




Ellipses in Trimetric




Axonometric Projections Using Intersections• Before computer automated

drafting, a method was devised to create axonometric projections using projections from orthographic views




Axonometric Projections Using Intersections

axonometric projection chapter 14. 2 technical drawing 13 th edition giesecke, mitchell, spencer,...

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