Axonometric Projection Chapter 14

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

Isometric Projection Lines of an isometric drawing that are not parallel to the isometric axes are called nonisometric lines These lines are not equally foreshortened

Isometric Projection 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

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