Design for assembly: the cheapest cost reduction available.

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.

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. It's also the build a robot or a vision-checked station handles best, so a design that takes the decisions off the line is ready for more automation when volumes justify it.

Fasteners are confessions

A screw is the line admitting the parts wouldn't stay together on their own. It's sometimes necessary and 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. For products sold in the EU with a portable battery inside, part of that story is becoming a requirement: from 18 February 2027, those batteries must be readily removable and replaceable by the end user, with limited exceptions. Design the battery's joinery to come apart in the owner's hands, not just to go together on the line.

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.

The agent-native lens: assembly that software can read

When the buyer sends an assistant. Two kinds of buyer now read the assembly. One is you, sending an agent to collect and compare quotes from several factories. It can only compare like with like if the pack is unambiguous: a consolidated bill of materials, one fastener specification, an assembly sequence written step by step. A fussy design invites each factory to price its own assumptions about labour, and those assumptions are exactly what an agent can't see in a quote. The other is your end customer's assistant, asked whether the battery can be swapped or which screws hold the back on. If your service information names the tools, the fasteners and the spare parts plainly, it has an answer to give.

When the business runs on agents. DFA becomes a check that runs on every CAD release instead of a workshop held once. An agent can compare the release with the last one and report what grew: part count, fastener types, drivers, any part that now loads from a second direction where the model carries that information. In a pilot build it can map the defect log onto the assembly steps and point to the step where errors cluster. Merging two parts is still an engineering trade-off (more tooling complexity for less labour), so a person makes it, and the engineering lead signs the DFA review before any request for quotation goes out.

Ready for what comes to the line next

Assembly is heading toward more automation, firmer service obligations and more software reading your geometry before a person does. A design with fewer parts, one direction and no decisions left on the line is ready for all three, and that work is still cheapest while the product only exists in CAD.