articles — studio notes

Design for assembly: the cheapest cost reduction available.

Teams negotiate unit prices for weeks and accept assembly labour as a law of nature. It isn't — most of it was decided in CAD, and it can be undecided there too.

skeelx — 24 aug 2026 · 4 min read

Every part is a tax

Each component in your product carries invisible fees: it must be sourced, stocked, inspected, presented to the line, handled, oriented and fastened — and every one of those steps can go wrong. The first DFA question is brutal and productive: does this part need to exist, or can it merge with its neighbour? Part consolidation — the boss moulded in rather than screwed on, the clip formed into the housing, one moulding doing three jobs — attacks unit cost, assembly time and defect surface simultaneously. Fewer parts, fewer problems is nearly a law.

the screwed-on version housing boss, screwed on clip, separate part bracket label plate six screws, two types, two drivers each part: sourced · stocked · inspected · presented · oriented · fastened — each step can fail consolidate the consolidated version parts load one direction — straight down housing — boss & clip moulded in chassis — self-locating one screw type, one driver position decided by geometry, not operator skill decisions on the line no decisions left to get wrong cost, time and defect surface fall together — and the quote follows the labour the factory can see parts illustrative — fewer parts, fewer problems is nearly a law
every part is a tax — consolidation is the refund

One direction, no decisions

The fastest assembly is a stack: parts loading from one direction, ideally straight down, each self-locating so position is decided by geometry rather than operator skill. Symmetric where orientation shouldn't matter; aggressively asymmetric where it must — a connector that fits two ways will be fitted the wrong way at exactly the rate statistics predicts. Design out the decisions and you've designed out both the seconds and the errors, which is why DFA and quality are the same project wearing different badges.

Fasteners are confessions

A screw is the line admitting the parts wouldn't stay together on their own — sometimes necessary, always costly: a part plus an operation plus a driver plus a torque to control. Rationalise ruthlessly: snaps and interlocks where the engineering supports them, and where screws must exist, one type, one size, one driver across the product if you can possibly manage it. Serviceability sets the boundary — the fastener a field technician needs is different from one sealing a disposable — so decide the service story first, then the joinery.

Why it pays double in China

An assembly-friendly design quotes better — factories price the labour and risk they can see — and it survives translation: a build that needs no tribal knowledge transfers to a new line, or a new factory, without the yield dip that punishes fussy designs. Run the DFA pass before quoting, not after: it's part of how our engineering practice preps every pack, and a pilot build is where the remaining seconds get found.

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