22-Mec-B5 Product Design and Development · May 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams, May 2014 — 07-Mec-B5 Product Design and Development. Three hours. Open book; no calculator permitted. Question 1 must be completed and is worth 40 marks; four of the six remaining questions are chosen, each worth 15 marks, for 100 marks in total. Only the first five questions as they appear in the answer book are marked, and the paper states that most answers are expected in essay form or as tables, figures and charts, with clarity and organisation carrying weight.
The paper prints 40 + 6 × 15 = 130 marks and a candidate attempts 40 + 4 × 15 = 100 of them. All seven questions are answered below, because this set is a study resource rather than an examination script. The arithmetic that appears is deliberately light — no calculator is allowed.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Technology 1: three-dimensional parametric CAD with model-based definition. A feature-based, history-driven solid model with a full assembly structure improves design quality in ways a drawing board cannot. Interference and clearance are checked automatically rather than by inspection; mass properties, centres of gravity and inertias fall out of the model; a change to a driving dimension propagates through every dependent feature and every drawing view; and configurations let variants be maintained as one controlled family rather than as divergent copies. Model-based definition takes it further by carrying tolerances, surface finish and process notes as product manufacturing information on the model itself, so the model — not a drawing derived from it — is the legal definition of the part.
Technology 2: engineering simulation. Finite-element stress, fatigue and modal analysis, computational fluid dynamics for flow and thermal behaviour, multibody dynamics for mechanisms, and statistical tolerance-stack analysis all do the same thing for design quality: they move the discovery of a failure from the prototype, where it costs a tool change, to the model, where it costs an afternoon. Their real value appears when they are used to explore rather than to confirm — design of experiments and optimisation over a parametrised model produce a design that is robust across the range of conditions it will actually meet, which no single prototype test can demonstrate.
Technology 3: additive manufacturing for rapid prototyping, closed by 3D scanning and coordinate metrology. Printing a part in hours converts abstract argument into physical evidence: fit, ergonomics, assembly sequence and user reaction are all things people judge badly from a screen and well from an object in the hand. Scanning and coordinate measurement close the loop in the other direction, bringing the as-built geometry back as a deviation map against the nominal model, which is how a designer learns what the process actually delivers rather than what the drawing asked for.
The three technologies deliver a fraction of their value if each is a separate island with a manual export between them, because every manual step is an opportunity for the analysed geometry, the printed geometry and the released geometry to be three different things. The interfacing strategy has five parts.
One master model in one controlled vault. A PDM or PLM system holds the single authoritative model with revision control, check-in and check-out, and an approval workflow. Every other tool takes a controlled copy from it and publishes its results back to it. This is the architectural decision on which the other four depend, and it is the one most often skipped.
Neutral, semantically rich exchange formats. Native CAD where the tools are from the same vendor; STEP AP242 where they are not, because AP242 carries product manufacturing information and assembly structure rather than dumb surfaces; and lightweight visualisation formats such as JT or 3D PDF for review by people who do not own a CAD seat. Choosing a format that loses the tolerances is how a supplier ends up making the wrong part.
Associative links rather than exports. Modern CAE is set up so the mesh, loads and boundary conditions are attached to named geometric faces of the CAD model, not to a dead copy of it. When the model changes, the analysis re-meshes and re-runs against the new geometry without being rebuilt. The equivalent on the manufacturing side is associative CAM toolpaths. This is what makes a design iteration cheap enough to do ten times instead of twice.
A defined path to the physical part and back. CAD to a tessellated build format — STL, or 3MF where colour and material data matter — with the tessellation tolerance chosen deliberately, since a coarse chord height is a real dimensional error introduced at the interface. Coming back, scan data is registered to the nominal model and reported as a coloured deviation map, and coordinate-measuring results feed the same comparison. Both are attached to the vault against the revision they were taken from.
A common data spine and disciplined process. One part-numbering scheme and one bill-of-materials structure shared by CAD, CAE, CAM and the enterprise system; a naming and revision convention that survives the round trip; and a rule that analysis and prototype results are stamped with the model revision they came from. Add automated regression checks — mass properties, interference, tolerance stack — run on each check-in, and the toolchain reports its own inconsistencies instead of waiting for a person to notice them.
Two cautions belong in a complete answer. Simulation and prototyping quality is bounded by the quality of the material data, boundary conditions and process assumptions behind them, so both must be validated against physical test at least once per material and process before their results are trusted unsupervised. And an additive prototype is generally not made by the production process, so it answers questions of form, fit and sequence well and questions of strength, creep and fatigue badly unless the process is the production one.
