Digital design and manufacture

A design team is developing a plastic drone arm that must be light but strong. Explain how CAD and virtual modelling would be used and what physical testing still remains.

1. 01Model parametrically

   Build a parametric 3D CAD model of the arm whose wall thickness and rib dimensions are editable values, so the geometry can be varied quickly during optimisation.

2. 02Simulate with FEA

   Apply the expected flight and crash loads in finite-element analysis to compute stress and deflection; thicken or rib the areas of high stress and thin the lightly-loaded areas to save weight, iterating on screen without making anything.

3. 03Confirm physically

   Once the model meets the targets, 3D print or mould a physical arm and test it under real loads, because the simulation's accuracy depends on its material data and assumptions - the virtual work guides the design, the physical test verifies it.

Result: Parametric CAD lets the arm's dimensions be varied quickly and FEA optimises strength-to-weight on screen, cutting the number of prototypes; a physical load test is still required to confirm the simulated result.

A firm needs 200 identical aluminium parts machined to a tolerance of plus or minus 0.1 mm. Explain why CNC is chosen over hand machining and outline the workflow.

1. 01Why CNC over hand work

   Hand machining 200 parts to plus or minus 0.1 mm would be slow and would vary from part to part; CNC positions the tool automatically to high precision and repeats the exact same toolpath every time, so all 200 parts are identical and within tolerance.

2. 02Outline the workflow

   Model the part in CAD; generate toolpaths and G-code in CAM; load the stock and run the G-code on the CNC mill, which cuts each part identically; a first-off is inspected against the tolerance before the batch runs.

3. 03Note the trade-off

   CNC's higher machine and programming cost is justified here by the precision and repeatability over 200 parts; for millions of parts, die casting would become cheaper per unit.

Result: CNC is chosen because it delivers the plus or minus 0.1 mm tolerance identically across all 200 parts; the workflow is CAD model to CAM toolpaths and G-code to CNC machining, with a first-off inspected before the batch - precision and repeatability justify the cost at this batch size.

A start-up needs a single functional prototype of a complex bracket with internal lattice reinforcement, needed within a day and likely to change several times. Recommend a manufacturing approach and justify it.

1. 01Match the need to the method

   The part is a one-off, geometrically complex (internal lattice) and likely to be revised - so a tooling-based or subtractive process is unsuitable; additive manufacture builds it directly from the CAD file with no tooling and can make the internal lattice that moulding or machining could not.

2. 02Choose the process

   SLS is a strong candidate because it fuses powder without support structures, so the internal lattice can be built and the part is strong and functional; FDM is the cheaper alternative if strength and internal geometry allow.

3. 03Justify against iteration

   Because there is no tooling, each design revision costs only another print, so the bracket can be iterated rapidly within a day - exactly the strength of 3D printing for prototyping.

Result: 3D printing is chosen because it builds the complex internal-lattice one-off directly from the model with no tooling and allows same-day iteration; SLS suits the strength and internal geometry, with FDM as a cheaper fallback - additive manufacture matches a complex, changing one-off far better than moulding or machining.

A manufacturer wants to hold as little stock as possible while never running short. Explain how EDI, MRP and scheduling achieve this and identify one risk.

1. 01Plan the materials

   MRP works back from the production schedule and the bill of materials to calculate exactly which components are needed and when, so only the required quantities are ordered - avoiding both shortage and excess stock.

2. 02Order automatically

   EDI sends the orders directly to suppliers' systems the moment they are triggered, with no manual re-keying, so materials arrive just in time and stock is kept low.

3. 03Identify the risk

   The whole plan depends on accurate data and reliable systems and suppliers: a wrong forecast or bill of materials, or a system or supplier failure, can either halt production or create shortages - so the data and supply chain must be dependable.

Result: MRP calculates precisely what is needed and when, and EDI orders it automatically just in time, letting the firm run on low stock; the risk is that inaccurate data or a system or supply failure can stop production, so reliability is essential.