How does computer-aided design change the way technical drawings are produced, and what can 2D and 3D CAD do that manual drawing cannot?
Describe and apply computer-aided design (CAD) to produce technical drawings and 3D models, and explain the advantages of CAD over manual drawing and its links to manufacture
A focused guide to CAD for HSC Industrial Technology Graphics Technologies. What CAD is, 2D drafting and 3D modelling, parametric design, the advantages over manual drawing, output and the link to CAM and manufacture.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
Computer-aided design has transformed graphics, and NESA expects you to understand and apply it. You need to describe what CAD is, use it to produce technical drawings and three-dimensional models, and explain its advantages over manual drawing and how it links to manufacture. CAD is now central to the graphics industry and to the Major Project in this focus area, where folios commonly include both manual and CAD-produced drawings, so this content is examined and practised directly.
What CAD is
Computer-aided design replaces the drawing board, tee-square and instruments with software that creates drawings and models electronically. The designer draws with precise numeric input rather than by hand, so geometry is exact, and the drawing exists as editable data rather than fixed ink on paper. CAD ranges from simple two-dimensional drafting to sophisticated three-dimensional modelling, and it is the everyday tool of the modern graphics, engineering and architectural industries.
Two-dimensional CAD
Two-dimensional CAD reproduces traditional technical drawing on the computer. The designer draws lines, arcs and shapes to exact dimensions, uses layers to separate information, and applies the same Australian Standards conventions for line types, dimensioning and sectioning as manual drawing. Because everything is numerically precise, drawings are perfectly accurate and easy to revise, copy and reuse.
Three-dimensional CAD and modelling
Three-dimensional CAD builds a virtual model of the object in space. The model can be rotated and viewed from any angle, rendered with materials and lighting, and used to automatically generate orthogonal views and pictorials. Many systems are parametric, meaning the model is driven by dimensions and relationships: change one dimension and the whole model and its drawings update. Three-dimensional models can also be analysed for fit, clash and even strength before anything is built, which removes errors early.
Advantages over manual drawing
CAD offers clear advantages, which the written paper often asks you to explain:
- Accuracy: geometry is exact, with no measurement or scaling error.
- Speed of editing: changes are made instantly without redrawing.
- Reuse and consistency: standard parts, symbols and templates are reused across drawings.
- Storage and sharing: drawings are stored, copied and sent electronically.
- Visualisation: 3D models and renderings show the design realistically before it exists.
The limitations are the cost of software and hardware and the skill and training needed to use CAD effectively.
Output and the link to manufacture
CAD drawings are output to printers and plotters for hard copy, exported in standard file formats for sharing, and, crucially, passed to manufacture. A CAD model can be sent to CAM (computer-aided manufacturing) software that generates the tool paths for CNC machines, so the design drives the cutting directly with no manual re-marking. Three-dimensional models can also drive 3D printers. This unbroken digital link from design to manufacture is one of the most important changes CAD has brought to industry and a key point to make in the written paper.
Using CAD in your folio
In this focus area your folio typically shows both manual and CAD-produced drawings, so you demonstrate the underlying drawing skills and your command of the software. Use CAD to produce accurate working drawings, present 3D visualisations of your design, and explain in your folio why CAD suited each task and how it links to making the project.
Exam-style practice questions
Practice questions written in the style of NESA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
2019 HSC1 marksCAD programs use vector images rather than raster images because A. raster images are too small for large projects. B. raster images rely on mathematical computations. C. vector images do not lose resolution when scaled or reproduced. D. vector images are able to incorporate detailed photographic information.Show worked answer →
The correct answer is C: vector images do not lose resolution when scaled or reproduced.
CAD stores drawings as vectors, that is as mathematical definitions of points, lines and curves. Because the geometry is defined by equations rather than a fixed grid of pixels, a vector drawing can be scaled, zoomed and reproduced at any size with perfectly crisp lines and no loss of resolution, which is essential for accurate technical drawings.
It is vectors, not raster, that rely on mathematical computation, so B is wrong; raster handles photographic detail, so D is wrong; and raster size is not the real issue, so A is wrong. So C is correct.
2019 HSC1 marksWhat equipment could a designer use to convert a freehand sketch into a form suitable for storage and transmission? A. Scanner B. Laminator C. 3D printer D. Flash driveShow worked answer →
The correct answer is A: scanner.
A scanner digitises a paper sketch by capturing it as an image file. Once the freehand sketch is a digital file it can be stored on a computer, edited in software and transmitted electronically, which is exactly what the question asks for.
A laminator (B) only seals paper in plastic, a 3D printer (C) outputs physical objects rather than digitising a drawing, and a flash drive (D) only stores files that are already digital. So A is correct.
2019 HSC2 marksA draftsperson is asked to produce a 'fly-through' of a building design. List the series of steps needed to produce the presentation.Show worked answer →
Award up to two marks for a sensible ordered sequence of steps.
Build the 3D model. Create an accurate 3D CAD model of the building from the plans, including the structure and key surfaces.
Apply materials and lighting. Add textures, colours and materials and set up lighting so the model looks realistic when rendered.
Set the camera path. Define a camera route through and around the model with keyframes for the viewpoint over time.
Render and output. Render the sequence of frames along the path and compile them into a video file for presentation.
Full marks need the logical order of model, then materials and lighting, then camera path, then render and output.