Technical drawing
Technical drawing is a means by which a designer can communicate a design to others in a design team, or to those responsible for manufacture/construction, in a complete and unambiguous manner. Various conventions have been developed over the years to support this process, most notably two-dimensional orthographic projections (i.e. plans, elevations, and sections) described above and three-dimensional metric projections (i.e. axonometric and oblique).
Introduction to three-dimensional visualization
Representing three dimensions on paper is a vital skill for designers, enabling them to communicate their ideas to other people, especially non-designers such as users, managers, and marketing personnel. There are several tried and tested drawing systems used to produce a realistic representation of an object such as perspective drawings, full-size elevations, and retouched photographs of models. These methods of drawing are used by designers to communicate different aspects of their designs to each other, to clients, and to those responsible for the manufacture/construction of the product design.
In order that a design is manufactured accurately and in accordance with the product’s specifications, standard drawing methods and conventions have been developed over the years, so that there can be no misunder-standings between all parties involved in the design process from conception to completion of a project. Some techniques such as isometric drawings are based on mathematical systems; others convey a larger degree of realism by applying perspective to the drawing. This section explores a range of drawing techniques utilized during the concept design stage.
One-point perspective, with one vanishing point toward which all lines, except those normally at right angles to the viewers’ sight line, will recede and converge.
A two-point perspective has two vanishing points, placed on the horizon to the left and right of the object.
A three-point perspective has the vertical lines of an object converging toward a third vanishing point directly below or above it.
Orthographic drawing
A central problem in drawing for design is how to represent three-dimensional objects on a surface that only has two dimensions. Orthographic drawing is one method of drawing used by designers to enable them to represent real or imagined three-dimensional objects on a two-dimensional surface. The other main drawing methods are oblique and perspective. The method of drawing chosen by a designer will depend on what he or she wishes to communicate in the drawing.
The multiview drawing—orthographic projections
This is a related set of orthographic projections that are known as plans and elevations. The plan, or top view, shows the view of an object as if taken from above. An elevation may be a front, side, or rear view, depending on how you orient yourself to the object or assess the relevant significance of its faces. A section is the view of an object as it would appear if cut through by an intersecting plane. Sections on an orthographic drawing show details it would not be possible to see with the naked eye. Cut solids in a section are shown crosshatched. And finally, the view of the base of an object, when required to be shown, can be referred to as a base view or base plan and is located above the front elevation in a first-angle projection and below the front elevation in a third-angle projection. A single plan, elevation, or section can only reveal partial information about an object, as the third dimension is flattened on to the drawing surface. Together, however, the projections are able to fully describe the object’s three-dimensional form.
Drawing conventions
There are two conventions for regulating the relationship between orthographic views: first-angle projection and third-angle projection, each indicated by a projection symbol. The difference between the two is in how the different views of an object are positioned on the drawing surface. In the layout of a first-angle projection, the plan is drawn first, then the elevation of the front face positioned immediately above it and the left-end elevation positioned to the right of the front elevation. In the layout of a third-angle projection, the views are arranged so that the front elevation is placed below the plan and the left-end elevation is positioned to the left of the front elevation. In any multiview drawing, the maximum possible number of views that can be shown of an object is six: plan, front elevation, rear elevation, base plan, left elevation, and right elevation. Each orthographic view represents a different orientation and a particular vantage point from which to view an object. Each plays a specific role in the communication of a design.
The method of projection you use will depend on what is most appropriate for the application. For drawing a long, thin product, a third-angle projection would be easier to read because the end elevation is placed to the left and adjacent to the front elevation.
Axonometric sketch of the Acapulco clock, by George Sowden for the first exhibition by Memphis, 1981.
Oblique projection drawing of the iconic Casablanca sideboard, by Ettore Sottsass for Memphis, 1981 (see p. 39).
Constructing a first-angle projection, as commonly used in the UK and Europe.
Constructing a third-angle projection, as commonly used in the United States.
Layout of drawings
Paper sizes used in North America are shown in the box below; the “A” series based on the international paper size standard, ISO 216, is normally used for all drawings outside North America. The drawing should be framed within a border. Anything within the border forms part of any contract requirements.
The title block should be located within the drawing frame on the lower right-hand corner. The following information should always be included in the title block: designer’s name/company name, drawing title, drawing number, date of drawing, and scale. All lines should be uniformly black, dense, and bold. Lines should be all in pencil or all in black Rotring (or similar) graphic pen. Drawing sheets have two formats: portrait, where the longest side is oriented vertically, and landscape, where the longest side is oriented horizontally. Every drawing should be drawn in proportion, i.e. to a uniform scale.
The scale used should be stated on the drawing as a ratio, e.g. scale 1:2. Do not use descriptions such as full-size or half-size. The scale that you choose for a drawing will depend on the size of your drawing sheet and the size of the object to be depicted. The scale should be large enough to allow easy and clear interpretation of the information. Details that are too small for clear dimensioning in the main representation of an object or building should be shown in a separate view to a larger scale.
Recommended scales to use are:
- For drawings at full size, i.e. actual size: 1:1
- For drawings smaller than full size: 1:2, 1:5, 1:10, 1:20, 1:50, 1:100, 1:200, 1:500, 1:1000
- For drawings larger than full size: 2:1, 5:1, 10:1, 20:1, 50:1
Standard paper sizes
In the United States paper sizes are as follows:
Letter = 8.5in x 11in (216mm x 279mm)
Legal = 8.5in x 14in (216mm x 356mm)
Junior Legal = 8in x 5in (203mm x 127mm)
Ledger = 17in x 11in (432mm x 279mm)
Tabloid = 11in x 17in (279mm x 432mm)
The “A” sizes are as follows:
A4 = 210mm x 297mm
A3 = 297mm x 420mm
A2 = 420mm x 594mm
A1 = 594mm x 841mm
A0 = 841mm x 1189mm (this nominally represents one square meter and forms the basis of the series)
Guidelines for drawing
In summary, when drawing, visualizing, and presenting design concepts you should adhere to the following points:
Visualize early
Don’t just visualize as a presentation tool, but as a concept generation device that can convey your concepts clearly and concisely to as wide an audience as possible.
Iterate often
Iterate as much as possible during the initial stages of the design process. This will help you generate ideas in a manner more conducive to evaluating a concept’s merits rather than falling for the superficial qualities of a particular visual.
Don’t overvisualize
The aim of concept generation is to generate just enough viable concepts as possible. Low-fidelity rapid sketches and models are far more useful at this stage of the design process than more polished techniques as they encourage debate.
Visualize neutrally
When evaluating alternate design options it really helps to keep the quality and style of each visual as similar as possible. By presenting designs in a neutral manner, you can shed a sense of ownership, and the efforts of the entire team can be evaluated on a level playing field.
Be aware of how people interpret visuals
You need to be fully aware of the subtle messages that different forms of visuals carry. For example, a rough pencil sketch has an immediacy that might imply an underdeveloped concept, while a photorealistic computer rendering may imply that a mere concept is, in fact, a finished design that is beyond criticism or change.