Produce and interpret engineering drawings, including detail drawings, assembly and exploded views, sectional views and tolerances, and describe technical illustration for instructions and manufacture

What this dot point is asking

Engineering drawing applies graphics to machines and manufactured products, and it is a major area of the Graphics Technologies focus area. NESA expects you to produce and interpret engineering drawings: detail drawings of single parts, assembly and exploded views showing how parts fit, sectional views, and the tolerances that control accuracy. You should also describe technical illustration that explains products and instructions. This is tested in the written paper and is often the basis of a graphics Major Project.

Detail drawings

A detail drawing fully describes a single component so it can be manufactured. It shows the part in orthogonal views, with every dimension, the material, the finish, tolerances and any notes a maker needs. Each part of a product has its own detail drawing, and together they form the documentation from which the parts are made. A good detail drawing leaves nothing to guesswork: someone who has never seen the part can make it correctly from the drawing alone.

Assembly and exploded views

Where detail drawings describe parts individually, assembly drawings show how they go together:

• Assembly drawings show the complete product with all parts in their assembled positions, often with a parts list (a bill of materials) keying numbered components to the detail drawings.
• Exploded views pull the parts apart along their axes of assembly, so you can see every component and the order in which they fit. They are the standard way to show how something is put together and are used throughout maintenance manuals and assembly instructions.

Sectional views

Many parts have internal features that hidden lines cannot show clearly. A sectional view cuts through the part along a defined section plane and hatches the cut surface, revealing bores, recesses and internal construction. Half sections, full sections and part sections suit different needs. Sectioning in engineering drawing follows the same standard conventions as in general technical drawing.

Tolerances and fits

Real parts cannot be made to a perfectly exact size, so engineering drawings state tolerances: the allowable variation above and below the nominal dimension. Where parts must fit together, the combination of their tolerances defines the fit, from a tight interference fit to a loose clearance fit. Tolerancing matters because too tight a tolerance is expensive to make while too loose a one lets parts fail to fit or function. Showing appropriate tolerances is a mark of real engineering understanding.

Technical illustration

Technical illustration takes engineering information and presents it clearly for an audience that may not read formal drawings:

• Instructional illustrations such as exploded assembly guides show a user how to put a product together.
• Maintenance and parts illustrations identify components for service and ordering.
• Catalogue and presentation illustrations show products attractively while remaining accurate.

Good technical illustration combines accuracy with clarity, using pictorial views, callouts and numbering so the reader understands without specialist training.

Using this in your project

An engineering graphics Major Project typically produces a coordinated set: detail drawings of each part, an assembly drawing with a parts list, an exploded view, and sectional views where needed, all to standard conventions with appropriate tolerances. In your folio, explain how the set fully documents the product for manufacture and assembly, which is exactly the competence the markers reward.