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Design and Management

Types of drawings

This unit of work addresses aspects of the following syllabus outcomes:

A student:

H3.1 is skilled in sketching, producing and interpreting drawings.

Extract from Stage 6 Industrial Technology syllabus. © Board of Studies, NSW, 1999

Different forms of drawings need to be produced for inclusion in a major project management folio. Drawings can take the form of pictorial drawings or orthogonal drawings. The type of drawing chosen depends on the information you are trying to convey and, it needs to be relevant to the focus area. Drawings can be done freehand, accurately drawn on paper or drawn using computer software. Each of these methods should be included when producing a major project management folio.

Freehand drawing

The importance of freehand sketching cannot be overestimated. Most original ideas find their first expression through the medium of a freehand sketch. Engineers usually prepare their designs and turn them over to the detail draughtsperson in this convenient form. Information concerning changes in design or covering replacement of broken parts or lost drawings is conveyed through sketches.

The degree of perfection required in a given sketch depends on its use. Sketches that are hurriedly made to supplement an oral description may be rough and incomplete. On the other hand, if the sketch conveys important and precise information to people it should be made as carefully as possible under the circumstances.

Freehand sketches should be used in the development of ideas when documenting the design and management of your major project.

Pictorial drawing

A drawing that represents three sides of an object in one view is a pictorial drawing. Orthographic views are two-dimensional. Two or more views of an object can convey an idea of shape and form to people who are familiar with this type of drawing.

Engineers, however, need to convey the idea of shape and form to persons untrained in engineering drawing. Pictorial views are used in these cases because of their three-dimensional aspect, which convey a full shape description to the viewer.

Some samples of common pictorial drawing methods may be viewed by accessing the following site:

http://www.stemnet.nf.ca/DeptEd/g7/pictorials.htm

However, note that Cabinet Projections are more commonly referred to as Oblique Projections in Australia. Other forms of pictorial drawing include dimetric drawing, trimetric drawing and planometric drawing.

Isometric drawing is the most commonly used method of pictorial drawing. Isometric drawings are built on three lines, called isometric axes. One is drawn vertically and the other two with the 30° set square either side of it. The intersection of these lines would be the lower front corner of a block with square corners. In commercial practice, isometric drawings are widely used because they can be prepared easily and the lengths of the lines scaled directly.

Orthogonal drawing

Orthogonal drawing is often referred to as orthographic drawing.

For an overview of orthogonal drawing visit the site:

http://www.stemnet.nf.ca/DeptEd/g7/ortho.htm

Practically speaking, all objects that a draftsperson is called upon to draw are three- dimensional. Techniques used in pictorial drawings are not satisfactory for working drawings since they cannot convey accurately the constructional features of the object.

To represent three-dimensional parts on the flat plane of the drawing paper in such a way that all features are shown in their true dimensions, and in their true relationship to other features on the part or object, a number of views of the part or object are drawn from different angles, and employ what is known as orthographic projection. Orthographic projection means right-angular, or perpendicular projection.

Orthographic drawings used to convey information about a part or object are known as detail drawings, architectural drawings or working drawings. All drawings should be drawn in third angle projection; each view shall be so placed that it represents the side of the object near to it in the adjacent view.

Working drawings

here are two types of working drawings:

assembly drawings.
detail drawings.

An assembly drawing is one in which two or more parts are shown fitted together. These drawings are made quite often to a reduced scale to show the general appearance of the unit. This indicates the relevant positions of the various parts. Assembly drawings may be either pictorial or orthographic.

The drawing of a single part or item giving all the information necessary for making it is called a detail drawing. This is the simplest form of working drawing and should consist of:

Carefully selected views
Well-located dimensions
Drawing to as large a scale as possible.

Architectural drawing

Architectural drawing is concerned with the representation and specification of buildings and structures. There are two main types of architectural drawings:

Sketch plans. In these, plans and elevations are used, but without working information. They are rendered in watercolour, pen and ink, pencil or crayon, to make them legible and attractive.
Working drawings. These form the most important class of drawings and include plans, elevations, sections and detail drawings which, when read with the specifications for details of materials, finish, etc., give all the necessary information for the erection of the building.

Reference:

A suitable reference for learning about, and learning to draw is:

Park A., Dodds K., and Bland S. (1989) Technology Drawing. Longman Cheshire: Melbourne.
Relevant chapters include chapters 8, 12, and 13.