HKDSE DAT common mistakes
HKDSE DAT · Understand the traps and how to avoid them.
Writing a design brief that names a solution ('design a wall-mounted rack with four hooks') instead of stating the user, context and problem to be solved.
Candidates want to look decisive and jump straight to the product they have already pictured, so the brief reads as a description of the answer rather than a statement of need. This then caps the marks for the whole design folio because evaluation later has nothing independent to test against.
What to do instead
Draft the brief as: target user + situation + need + constraints + what success looks like, with no product noun. Test it by asking whether two different products could satisfy it; if not, rewrite. Keep the brief visible through the project and check each design decision against it.
Treating the design process as a linear checklist and skipping iteration: research, then one idea, then a final drawing, with no evidence of testing, feedback or revision.
School projects are often run to a deadline where producing a finished artefact feels like the goal, and candidates believe a clean, tidy sequence scores better than a messy one. Examiners, however, reward evidence of evaluation and modification.
What to do instead
Build at least two documented loops: after concept selection, show user or expert feedback and what changed; after prototyping, show a test result, a fault found, and the modification made. Label each loop on the folio so it is unmistakable.
Describing materials by name only ('use plastic', 'use metal') without justifying choice against function, manufacturing process, cost, durability or sustainability.
Candidates memorise material names from textbooks but have not practised linking properties to a specific design decision, so justification is replaced by assertion. Marks are lost where the question asks for reasons.
What to do instead
For every material or component decision, write a short justification chain: required property, candidate materials, comparison on that property plus one secondary factor (cost, recyclability, availability), chosen material, and the trade-off accepted. Use a small comparison table rather than prose.
Naming a manufacturing process without matching it to the material, batch size or geometry, for example specifying injection moulding for a one-off large hollow shell.
Processes are learned as a list rather than as decisions governed by volume, tooling cost, wall thickness and shape. Under exam pressure the most familiar process is written down regardless of fit.
What to do instead
For each process, memorise three trigger facts: typical batch size, tooling or set-up cost, and a geometry or material constraint. Before writing, state the batch size and material of the product, then select the process that satisfies both, and say why the alternative was rejected.
Drawing orthographic or isometric views with missing hidden detail, inconsistent line types, no centre lines, or dimensions that do not sum correctly.
Candidates focus on making the drawing look like the object and treat conventions as decoration. They also work freehand without projecting from a base view, so views disagree with each other.
What to do instead
Adopt a fixed drawing routine: choose and lightly block the front view, project all other views from it with construction lines, then apply line conventions (visible, hidden, centre, dimension, projection) and finally check that each dimension appears once and the totals close. Practise under time with a checklist you tick off.
Producing a final design that ignores stated constraints such as overall size, budget, standard component sizes, ergonomic reach or safety requirements introduced in the question.
Candidates design in the abstract and only re-read the constraints when writing the evaluation, by which point the concept is fixed. Numeric constraints are especially easy to overlook.
What to do instead
Copy every constraint into a numbered list at the start and convert each into a measurable criterion (maximum mass, maximum cost, minimum clearance). Annotate each concept sketch with the relevant numbers, and include a compliance table in the evaluation showing measured or calculated values against each criterion.
Describing a control system or mechanism qualitatively ('a sensor detects the object and the motor moves the arm') without a block diagram, input/output states, or consideration of what happens when a condition fails.
Candidates are more comfortable with narrative than with system representation and do not realise that a block diagram is itself the answer being marked. Failure states are rarely taught explicitly, so they are not considered.
What to do instead
Practise converting any described system into input, process, output blocks with signal direction arrows, then add a state table listing normal, fault and safe states. For mechanisms, sketch the linkage or gear train and state the resulting motion, speed change and direction change.
Ignoring ergonomic and anthropometric data, sizing a product to the candidate's own body or to a guessed average rather than to a stated percentile and user group.
Personal experience feels like valid evidence, and percentile tables are seen as unnecessary detail. The result is a product that fits the designer but not the intended user.
What to do instead
State the user group and the percentile you are designing for (for example 5th percentile female reach for access, 95th percentile male for clearance), quote the dimension used, and show it applied on a dimensioned drawing. Where adjustability is the answer, show the adjustment range and the percentiles it covers.
Writing an evaluation that only praises the outcome ('the product is attractive, useful and meets the brief') with no measured evidence, no limitations and no further development.
Evaluation is left to the end and written from memory of intentions rather than from test data. Candidates fear that admitting weaknesses loses marks, when the opposite is true.
What to do instead
Evaluate against the numbered criteria set at the start, one line each, with the evidence source (test, user trial, measurement, calculation). Then list at least two genuine limitations and one specific, feasible further development with the reason it would improve the product.
Treating sustainability as a single sentence about recycling, without addressing material selection, energy in manufacture, product lifetime, disassembly or end-of-life routes.
Sustainability is often taught as a slogan rather than as a set of design decisions, so candidates cannot see where to apply it in their own work.
What to do instead
Apply a short lifecycle checklist to the chosen design: material source and recyclability, number of materials and whether they can be separated, energy intensity of the chosen process, expected lifetime and repair options, and end-of-life route. Report one specific change made as a result and the trade-off it created.