Communication with the general public - informs the general public, for example illustrated instructions found in the manuals for vehicles and consumer electronics. This type of technical illustration contains simple terminology and symbols that can be understood by the lay person and is sometimes called creative technical illustration/graphics.
Specialized engineering or scientific communication - used by engineers/scientists to communicate with their peers and in specifications. This use of technical illustration has its own complex terminology and specialized symbols; examples are the fields of aerospace and military/defense. These areas can be further broken down into disciplines of mechanical, electrical, architectural engineering and many more.
Communication between highly skilled experts - used by engineers to communicate with people who are highly skilled in a field, but who are not engineers. Examples of this type of technical illustration are illustrations found in user/operator documentation. These illustrations can be very complex and have jargon and symbols not understood by the general public, such as illustrations that are part of instructional materials for operating CNC machinery.
As Designers, we produce illustrations for inhouse publications, and also can produce an illustration to insert within documentation. As illustrators. We produce line and colour illustrations from any source information, by viewing the actual equipment to working from engineering drawings. We use several basic mechanical drawing configurations called axonometric projection. These are: Parallel projections (oblique, planometric, isometric, dimetric, and trimetric), and many types of perspective projections (with one, two, or three vanishing points). Technical illustration and computer-aided design (CAD) can also use 3D and solidbody projections, such as rapid prototyping.In the natural sciences, "scientific illustration" refers to a style of drawing using stippling and simple line techniques to convey information with a minimum of artistic interpretation.
Most commonly now, we work from many electronic formats, but mainly STEP or IGES. Whilst CAD has opened the door to the creation of an illustration at the click of button, in reality, it is not always as simple as that. Quite often an assembly can have more than one CAD file, from different sources with little or no interface detail between them, this is where the skill of a technical Illustrator does bridge the gap. Most illustrations can be produced to any specification required. JSP186, JSP(D)543, ATA iSpec 2200, S1000D. My software of choice is Isodraw, though Ialso utilise Solidworks 3dVIA for colour work and animations.