Engineering Drawing: A Comprehensive Guide for Biomedical Engineering Students, Lecture notes of Engineering Drawing and Graphics

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Engineering

Drawings

A short series of lectures on Engineering Drawing as Part of ENGG Introduction to Biomedical Engineering 1 By Paul Briozzo

What

is

an

Engineering

Drawing

An Engineering Drawing is a technical (not artistic) drawing which clearly defines and communicates a design to other interested parties. Other parties may have an interest in design collaboration, procurement / purchasing, costing, manufacturing, quality control, marketing, handling / packaging.

Consider

the

following

description

of

a

“V

Block”

MATERIAL: CAST IRON

Pictorial

Freehand

Lunar Module Landing Gear Plans, NASA, 1969

Examples

of

Layout

Drawings

Proposal Drawing Engineering drawing by Harry C. Shoaf (Space Task Group Engineering Division) of the proposed ʺ lunar lander ʺ to be used with an advanced version of the Mercury spacecraft. (Shoaf, Drawing, Nov. 15, 1961.) Surveyor 1 , Lunar Lander, 1969

The

History

of

Engineering

Drawing

Free

Hand

Sketches

- Leonardo

DaVinci 1500

AD

Sforza monument Anatomical study of the arm c Rhombicuboctahedron Design for a flying machine c

Graphical Projections Projections Axonometric/ Isometric Orthographic Oblique Parallel Projection Perspective Orthogonal 1 st Angle 2 nd Angle 3 rd Angle 4 th Angle

Method

and

Rules

of

Projections

Select a view from the most advantageous position.

Observe overall structure first. - Note: parallelism, proportions and alignment.

Method Rules

of

Projection

Object viewed from

Parallel lines remain parallel.

Proportions remain unchanged. - Circles are always ellipses with the major axis of ellipse perpendicular to the polar axis of circle. - Transformation of

angles.

Parallel

Projection

Axonometric/ Isometric Orthographic Oblique Parallel Projection Orthogonal 1 st Angle 2 nd Angle 3 rd Angle 4 th Angle

Cavalier views are not preferred. They show lines which represent the depth of the object as being disproportionally long. Even though they are parallel to each other, depth lines appear to diverge away from each other.

Cabinet views are preferred over Cavalier. The issue of depth disproportionality and divergence is “somewhat” eliminated by halving the depth dimension.

Oblique

Projection

Cavalier and Cabinet Projections Cavalier Cabinet

Oblique

Projection

Basic Rules

Place the object so that the view with the most detail is parallel to the picture plane.

Place the object so that the longest dimension runs horizontally across the sheet.

Axonometric

Projection

Projection lines are perpendicular to Projection Plane.

Principal axes inclined to Projection Plane. -

Isometric (Equal Scaling)

Dimetric

Trimetric

Isometric

Dimetric