Isometric and orthographic drawing, working drawings, CAD. Drawing understanding appears in many questions.
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GCSE DT RevisionTechnical Drawing and CAD
Key facts
Types of technical drawing
Isometric — 3D drawing. Vertical lines stay vertical; horizontal edges drawn at 30° to horizontal. All lines are true length. Quick to draw, good for communicating 3D form.
Orthographic projection — multiple 2D views (front, side, plan) arranged systematically. 3rd angle preferred in UK/AQA. Used for manufacturing.
Working drawing — fully dimensioned orthographic drawing for manufacturers. Includes tolerances, material, surface finish, scale, title block.
Drawing conventions: solid outline = visible edges. Dashed lines = hidden detail. Chain lines = centre lines and axes of symmetry.
Exploded drawing — components separated to show assembly relationship.
Files exported directly to CNC/laser/3D printer for CAM manufacture.
Advantages vs hand drawing: easy to edit, precise dimensions, stress simulation, motion analysis, share instantly, no physical prototype needed early on.
Disadvantage: expensive software/hardware, steep learning curve, slower than sketching for initial ideas.
Rapid prototyping — CAD file → 3D print quickly for testing before committing to tooling.
Exam questions — 5 questions · 12 marks · real AQA 8552 past papers
Extended questions included — read the hint. AI marks against the AQA 8552 mark scheme.
1 markIsometric angleAQA 8552 style
On an isometric drawing, at what angle to the horizontal are the lines representing horizontal edges drawn?
A 45°
B 60°
C 30°
D 15°
1 markHidden detail linesAQA 8552 style
In a working orthographic drawing, what do dashed lines represent?
A The outline of the object
B Centre lines and axes of symmetry
C Edges and features hidden behind other parts of the object
D Dimension lines showing measurements
4 marksAdvantages of CAD over hand drawingAQA 8552 style
Evaluate the advantages of CAD software over hand drawing for designing a new product. (4 marks)
Hint: At least THREE specific advantages and ONE honest limitation. Be specific — not just "it is better."
+40 XP
2 marksWorking drawing requirementsAQA 8552 style
State two pieces of information (other than the shape of the object) that must be included on a working drawing. (2 marks)
Hint: Think: what does a manufacturer actually need to know beyond the shape? Size (dimensions), precision (tolerance), what to make it from (material), how smooth (surface finish).