Graphics – Drawing Techniques (IGCSE Design & Technology 0445)
This set of notes covers every graphic‑product requirement of the Cambridge IGCSE Design & Technology (0445) syllabus. It is organised to match the syllabus structure, links directly to the assessment objectives, and includes concise reminders of the common‑content and specialist‑option material that must be understood alongside the drawing techniques.
1. Syllabus Overview & Assessment Objectives
| Component | Key Content | Assessment Objectives (AO) |
|---|
| Common content (Product design) |
Need analysis, brief, specification, research, idea generation, selection, development, planning, realisation, testing, evaluation, health & safety, sustainability, design in society |
AO1 30 % – knowledge & understanding
AO2 40 % – application of knowledge
AO3 30 % – analysis & evaluation |
| Specialist option – Resistant Materials |
Material families, properties, preparation, shaping, joining, finishing |
AO1 30 %
AO2 40 %
AO3 30 % |
| Specialist option – Systems & Control |
Structures, mechanisms, electronics, control circuits, sensors, actuators |
AO1 30 %
AO2 40 %
AO3 30 % |
| Graphic products (Drawing techniques) |
Freehand, orthographic, isometric, dimetric/planometric, perspective, sections, exploded views, nets, ellipses, scaling, CAD integration |
AO1 20 % – terminology & conventions
AO2 70 % – accurate production of drawings
AO3 10 % – critique of drawing quality |
Project (Component 2) checklist – the eight stages of the design cycle and the graphic‑product tasks that normally accompany them:
- Identify need & write a brief – sketch concepts, note key dimensions.
- Research & develop a specification – produce a table of requirements, include tolerances.
- Idea generation – freehand sketches, mind‑maps, annotated diagrams.
- Idea selection – evaluation matrix, annotate chosen concept with orthographic views.
- Development – detailed orthographic, isometric and section drawings; CAD models.
- Planning – work‑breakdown, material list, exploded view of assembly.
- Realisation (making) – develop nets, mark cutting lines, record any modifications.
- Testing & evaluation – annotate test results on drawings, suggest improvements.
2. Common Product‑Design Content (required for all candidates)
2.1 Need identification & design brief
- Analyse the problem, target user, and context.
- State the purpose, functional requirements and any constraints (size, cost, material, safety).
- Write the brief in clear, numbered statements – this becomes the reference for the whole project.
2.2 Research & specification
- Gather information from sources (catalogues, internet, interviews).
- Summarise findings in a specification table: dimensions, performance, durability, environmental impact.
- Where required, give tolerances (e.g. ±0.5 mm) and reference datum lines.
2.3 Idea generation & selection
- Freehand sketching, thumbnail drawings, and annotated diagrams to explore alternatives.
- Use an evaluation matrix (criteria vs. concepts) to justify the chosen solution.
2.4 Development & planning
- Produce detailed orthographic, isometric and section drawings.
- Create an exploded view and a work‑break‑down schedule.
- List all materials, tools and joining methods.
2.5 Realisation (making)
- Follow the development drawings; record any deviations.
- Use appropriate health‑and‑safety precautions (see 2.6).
2.6 Health & safety
- Identify hazards (sharp tools, hot surfaces, chemicals).
- Use the standard safety symbols (e.g., goggles, gloves, ventilation).
- Always wear personal protective equipment (PPE) and keep a tidy work area.
2.7 Sustainability & design in society
- Consider life‑cycle: raw material extraction → manufacture → use → disposal.
- Choose recyclable or renewable materials where possible.
- Assess energy consumption, waste generation and the product’s social impact.
3. Specialist Options – Key Knowledge
3.1 Resistant Materials (Option 1)
- Material families: woods (hard/soft), metals (ferrous, non‑ferrous), plastics (thermoplastic, thermoset), composites (fibreglass, carbon‑fibre), ceramics.
- Properties to consider: density, strength, stiffness, thermal conductivity, corrosion resistance, workability.
- Preparation & shaping processes: sawing, filing, drilling, turning, milling, bending, moulding, casting, laminating.
- Joining methods: adhesives, mechanical fasteners (screws, rivets, bolts), welding, soldering, interlocking joints.
- Finishing: sanding, painting, varnishing, anodising, powder coating.
3.2 Systems & Control (Option 2)
- Structures: forces, moments, stress, strain, simple trusses, beams, columns.
- Mechanisms: levers, gears, cams, linkages, pulleys, springs – focus on motion, speed ratio and force amplification.
- Electronics & control: basic circuit symbols, series/parallel connections, switches, relays, sensors (temperature, light, pressure), actuators (motors, solenoids), simple logic (AND, OR, NOT).
- Testing & safety: continuity testing, load testing, use of multimeter, isolation of live parts.
4. Graphic‑Product Requirements (Drawing Techniques)
4.1 Formal Drawing Standards
4.1.1 Line‑type conventions (BS 8888)
| Line type | Symbol | Purpose |
|---|
| Visible solid | ───── | Edges that can be seen in the view |
| Hidden (short‑dash) | ‑‑‑‑‑ | Edges obscured by the object |
| Centre (chain‑dot) | ╌╌╌╌╌ | Axes of symmetry, circles, cylinders |
| Construction (thin solid) | ——— | Guidelines not part of the final drawing |
| Section (thin dash‑dot) | ‑·‑·‑· | Cutting plane in sectional views |
4.1.2 Dimensioning rules
- Place dimensions outside the object whenever possible; use extension lines that are at least 3 mm long.
- Show overall dimensions first, then detailed dimensions for features.
- All dimensions are in millimetres (mm) unless the brief states otherwise.
- Indicate tolerances only where the specification requires them (e.g. 20 mm ± 0.2 mm).
- Establish a datum line (reference edge or centre line) and dimension all other features from it.
- Include a title block on every sheet containing:
- Student name, class, date
- Drawing number and title
- Scale (e.g. 1 cm = 5 mm)
- Projection method (first‑angle or third‑angle)
- Revision date (if applicable)
4.1.3 Projection methods
- First‑angle projection – front view in the centre, plan below, side elevation to the right. Predominantly used in the UK and Europe.
- Third‑angle projection – front view in the centre, plan above, side elevation to the left. Used in the USA.
- Schools must adopt one method and apply it consistently throughout the exam.
4.1.4 Drafting aids
- Technical pens (0.3 mm, 0.5 mm, 0.7 mm) for line weight control.
- Scale rulers (1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100).
- Set squares, T‑squares, protractors for orthogonal and angled lines.
- Templates (circles, ellipses, squares, hexagons) and flexicurves for smooth curves.
- CAD software (AutoCAD, Fusion 360, SketchUp, SolidWorks) – use layer management to assign line types, and enable hidden‑line removal for technical perspectives.
4.2 Freehand Drawing
- Pencil selection: HB–2B for shading, H for fine outlines.
- Grip & movement: hold the pencil loosely; use whole‑arm motion for large shapes and wrist for detail.
- Practice routine: daily sketches of basic shapes (circle, square, triangle) and shading techniques (hatching, cross‑hatching, stippling).
- Dimensions: add only essential dimensions with a ruler; keep the sketch fluid and avoid over‑detailing.
Assessment focus (AO2)
- Clarity of concept and intention.
- Correct proportion and relative size of elements.
- Effective use of line weight to emphasise important features.
4.3 Orthographic Projection
4.3.1 Standard views & projection planes
| View | Projection plane | Shows |
|---|
| Front (Elevation) | Vertical (YZ) | Height × Width |
| Top (Plan) | Horizontal (XZ) | Length × Width |
| Side (Side elevation) | Vertical (XY) | Height × Depth |
4.3.2 Step‑by‑step procedure (first‑angle example)
- Choose the projection method and draw the layout grid (baseline and vertical datum).
- Sketch the front view first using visible‑solid lines; add hidden‑line dashes for obscured edges.
- Transfer key dimensions vertically to the top view and horizontally to the side view, keeping the same scale.
- Insert centre lines for symmetry and apply the correct line‑type symbols.
- Check alignment of corresponding points across all three views (height, width, depth must match).
- Label each view (e.g., “Front view – 1st‑angle”) and complete the title block.
4.3.3 Hidden‑line and section conventions
- Hidden edges – short‑dash (‑‑‑‑‑).
- Section lines – thin dash‑dot (‑·‑·‑·) spaced 3 mm apart.
- Section symbol – a thick dash‑dot line “⧈” with a leader arrow indicating the cutting plane.
4.3.4 CAD integration
In CAD the orthographic views are generated automatically from a 3‑D model. Ensure the drawing style is set to “Technical” so that line types, scales and projection method match the manual standards.
4.4 Isometric Drawing
4.4.1 Geometry
- Three principal axes are equally inclined to the horizontal; each axis makes 30° with the baseline.
- All axes use the same scale – true‑scale representation of height, width and depth.
4.4.2 Construction steps
- Draw the isometric axes: two lines at 30° above the horizontal and one vertical line.
- Mark the chosen scale on each axis (e.g., 1 cm = 5 mm).
- Plot points by measuring equal distances along the axes.
- Connect points with visible solid lines; use short‑dash for hidden edges.
- Apply centre‑line symbols for cylindrical features.
4.4.3 Advantages
- Shows all three dimensions simultaneously.
- No perspective distortion – true scale on each axis.
- Can be produced accurately with ruler, set square and protractor.
4.4.4 CAD use
Most CAD packages have an “Isometric” visual style that automatically aligns the model to the 30°/30°/vertical axes, allowing rapid production of isometric line drawings.
4.5 Dimetric / Planometric (Axonometric) Drawing
4.5.1 Geometry
- Two axes are drawn at equal angles (commonly 30°) to the horizontal; the third axis is at a different angle (often 42°) to give a more realistic appearance.
- Scales are not uniform: a separate scale is marked for the two equal axes and for the third axis.
4.5.2 Construction steps
- Draw the two equal axes at 30° to the baseline.
- Draw the third axis at the chosen angle (e.g., 42°).
- Mark the appropriate scales on each axis.
- Plot points and connect edges using the same line‑type conventions as for isometric drawings.
4.5.3 When to use
- When the plan view must remain true‑to‑scale (e.g., floor plans combined with a 3‑D view).
- When a slightly more realistic visual impression is desired without full perspective.
4.6 Sectional & Exploded Views
4.6.1 Sectional views
- Indicate the cutting plane with a thick dash‑dot line and a leader arrow.
- Show the cut surface with evenly spaced hatch marks (3 mm spacing).
- Dimension features directly on the sectional view; reference the original datum where necessary.
4.6.2 Exploded views
- Separate components along their assembly lines to reveal how parts fit together.
- Use thin construction lines (———) to indicate the direction of movement.
- Number or label each component (e.g., “1 – Base plate”).
- Often combined with a short “assembly sequence” diagram showing the order of construction.
4.7 Developments (Nets)
- Unfold a 3‑D shape into a 2‑D pattern that can be cut and folded.
- Maintain true dimensions – the net must be drawn at the same scale as the orthographic views.
- Use solid lines for cut edges and dotted lines for fold lines (mount or valley).
- Label each face (A, B, C…) and indicate the direction of the fold.
4.8 Ellipses
- Represent circles viewed in perspective or on a sloping plane.
- Construction methods:
- Ellipse template or flexible curve.
- In CAD, draw a circle and apply a “skew” or “scale‑Y” transformation.
- Key parameters: major axis (a), minor axis (b), tilt angle (θ) relative to the horizontal.
- Label axes when required for dimensioning.
4.9 Perspective Drawing
4.9.1 Types of perspective
| Perspective | Vanishing points | Typical use |
|---|
| One‑point | 1 (on horizon) | Objects facing directly towards the viewer. |
| Two‑point | 2 (off‑centre on horizon) | Objects rotated away from the viewer. |
| Three‑point | 3 (two on horizon, one above or below) | Extreme viewpoints – looking up or down. |
4.9.2 Construction steps – one‑point example
- Draw a horizontal horizon line at eye level and mark the vanishing point (VP).
- Sketch the front face as a rectangle perpendicular to the picture plane.
- From each corner of the front face, draw lines converging to the VP.
- Decide the depth of the object; close the shape by drawing a line between the two converging lines at the chosen depth.
- Add details (windows, doors, textures) using the same vanishing lines to maintain consistency.
- Apply atmospheric perspective – objects further away are lighter, less contrast.
4.9.3 Scaling in perspective
- Near objects are larger; use a “scale reduction factor” (e.g., 1 cm at the front = 0.5 cm at the back) to keep proportions realistic.
- In CAD, adjust the camera distance and field of view; enable hidden‑line removal for a “technical perspective”.
4.10 Scaling – Enlarging & Reducing
- Scale ratio = new size ÷ original size. Common ratios: 1:2 (enlarge), 1:5 (reduce), 2:1 (double).
- When using a scale ruler, select the appropriate scale and measure directly.
- In CAD, use the “Scale” command or change the drawing scale in the layout tab.
- Always note the scale on the title block and on any enlarged or reduced detail views.
4.11 Materials & Modelling (Graphic‑Product Media)
| Material | Typical use | Joining / fixing methods |
|---|
| White drawing paper (A3, A4) | Sketches, orthographic & isometric drawings | None – drawing directly on surface |
| Card / Corrugated card | Physical prototypes, 3‑D models, nets | Adhesive (PVA glue), slots, flaps |
| Plastic sheets (PVC, acrylic) | Transparent views, component mock‑ups | Solvent cement, screws, adhesives |
| Foam board | Lightweight 3‑D models, presentation boards | Hot‑glue, double‑sided tape |
| CAD output (PDF, DWG) | Digital submission, large‑format prints | Not applicable – digital file |
Choose the medium that best demonstrates the required drawing technique and meets the brief’s constraints (size, durability, cost).