Engineering products from first principles

Anonymised: delivered for a Portuguese manufacturer shown here as “the manufacturer”. Figures are illustrative and carry no client data or identifying product detail.

The challenge

The manufacturer faced a strategic product decision for a new range of flushing systems: how best to cover a spread of market requirements. Two development branches were on the table — a pair of simpler, cheaper products that each serve part of the market, or a single, more complex product flexible enough to answer more requirements on its own. The first keeps each product cheap but doubles production complexity; the second carries a higher unit cost yet covers more of the market with one line. Picking wrong is expensive in tooling and production, so the goal was to make the call early, on evidence rather than instinct — and then to engineer the chosen product to a standards-compliant prototype.

What we did

• Techno-economic analysis — benchmarked competitor and candidate products on technical and economic terms to compare the two strategies like for like, then captured the strategic trade-offs in a SWOT.
• Ideation, modelling and prototyping — a calibrated parametric hydraulic model to steer the design, CAD iteration on a living version map, and 3D-printed prototypes tested in water within days.
• DOE, root cause and lab testing — a 2³ factorial experiment and root-cause analysis run on our own bench, then a regression model and an optimisation against the European flushing standard.

Approach

1 — Benchmark and cost the options

We put the two development branches side by side, and against the competition, on two levels.

Technical. We reverse-engineered competitor and candidate products — counting components, weighing raw material by family, and estimating production cost — then benchmarked real-world performance in a standard application. That turned each option into a comparable bill of materials and a like-for-like performance baseline.

Economic. We translated the technical picture into unit cost and required investment — raw material, production, mould and assembly-line amortisation — normalising every option so we compared apples to apples. The two strategies, a two-product range and a single flexible product, were costed across each variant.

SWOT. Finally we set the two solutions in a SWOT to capture the strategic trade-offs the numbers alone miss — chiefly that two products are individually cheaper but multiply production complexity, while the single product costs more per unit yet buys flexibility and broader market coverage.

2 — Ideate, model, and prototype

With the strategy set, we moved from problem to hardware in tight loops. We framed the functional targets — the full and reduced flush volumes required by the European flushing standard — and ideated the mechanisms to hit them.

To steer the design rather than guess, we built a parametric hydraulic model of the valve — volumes, flow rates, buoyancy, weight and timing — and calibrated it against bench measurements. The model predicts how each geometric change moves the discharge volume (raise the float, narrow a tube, shift the equilibrium point), so design decisions were made on physical insight, not trial and error.

Then we iterated in CAD on a living version map and 3D-printed every candidate to test it in water within days — tube diameters, float volumes, seal cones, counterweights — keeping what worked and shelving what didn’t. Several prototype generations in, the full flush was on target and the design was consolidating toward fewer, simpler parts.

3 — Prove it: DOE, root cause, and our own bench

When early prototypes under-shot the target flush, we didn’t guess. We ran a root-cause analysis, mapping every contributor to discharge volume — flow rates, buoyancy, weight, and dynamic effects such as surface tension and the float’s piston effect — and tested the suspects one by one.

To pin down what actually controls the flush, we designed a 2³ factorial experiment — three factors (tank water level, full-flush window, reduced-flush window), eight runs — and ran every test ourselves on a bench rig, timing each flush and measuring discharged volume and flow by hand. This is the part most consultancies outsource or skip; we did the work.

Because the effects were essentially linear, we fitted a regression model — a perfect fit on the orthogonal design — and used it to run thousands of virtual flushes. Scoring each setting by its distance to the standard’s acceptance windows, a Monte-Carlo search found the regulation closest to the standard.

The payoff is a product decision: a single factory regulation can satisfy both the 6/3 L and 4/2 L variants — fewer product codes, simpler assembly, and a path to removing the adjustment windows altogether.

Outcome

The techno-economic analysis accelerated the strategic decision, and the suggested path was implemented. From there we carried the chosen product to a validated, standards-aligned prototype — and left the manufacturer with a calibrated model that lets them optimise regulations without returning to the bench.