A cable assembly programme placed its order against a connector drawing and received an assembly whose overmould covered the connector’s latch. The conductor, the gauge and the length were all correct; the tool had been cut before the latch position was confirmed, and the moulding was the part that had never been drawn.
Custom cable assembly: the four cost lines
The components, the tooling, the assembly time and the test.
Each is quoted separately by a supplier who builds cables regularly, and each behaves differently as the quantity rises. The tooling is a fixed charge, the components and the assembly time scale with the order, and the test sits between the two depending on how much of it is sampled.
The assembly that covered the latch
The drawing described the connector and not the moulding.
The overmould was designed around the connector body, and the latch sits outside that envelope. Because the tool had been cut before a moulded sample was seen, the correction was a tool modification rather than an adjustment, and the delay was the tool shop’s queue rather than the assembly line.
Cost line one: the components
Three parts, and the third moves most.
The connector pair, the conductor and the jacket material, and any component inside the connector such as an identification element. The first two are quoted from a catalogue, and the third is where a specification change shows, because adding a component to the connector assembly adds a soldering step as well as a part.
Cost line two: the tooling
Two tools, and only one of them is usually visible.
The overmould tool, which shapes the finished assembly, and the test fixture, which holds the assembly during measurement. The first appears in a quotation as a die or a mould, and the second is often omitted, which is why the first invoice can be larger than the quotation that preceded it.
Cost line three: the assembly time
It scales with the number of operations.
Stripping and tinning, soldering or crimping, the component fitting, the moulding cycle and the final inspection are each a step. A cable with two conductors and one component has four steps; a shielded multi-conductor assembly with two components has more, and the difference appears in the unit price rather than in the tooling.
Cost line four: the test
Three levels, and the choice is commercial.
A continuity and short check on every assembly, the negotiated tier on a sample, and the pull and bend cycles on a sample per build. The first is cheap per unit and catches assembly errors; the other two describe the design, and repeating them on every unit adds cost without adding information.
| Cost line | Behaviour as quantity rises | Where it appears | Common omission |
|---|---|---|---|
| Components | Falls at purchasing thresholds | Unit price | The component inside the connector |
| Tooling | Fixed | Separate line | The test fixture |
| Assembly time | Falls with volume | Unit price | The added step from a new component |
| Test | Partly fixed, partly per unit | Mixed | The sample tests behind the claim |
Step one: freeze the mechanical drawing
It includes the moulding envelope.
The drawing states the connector positions, the bend radius at the exit, the overmould’s outer dimensions and the latch clearance. A drawing that stops at the connector body leaves the moulding to the tool maker, and the tool maker’s interpretation is what the first sample will show.
Step two: approve a moulded sample before the tool is finalised
It is the cheapest way to find an envelope problem.
A soft tool or a machined prototype produces a sample that can be fitted to the device and inspected for clearance. Where the programme is confident in the drawing, the sample still costs less than a tool modification and its queue.
Step three: define the tests with their sample sizes
Three tests, and each names a quantity.
The per-unit continuity check, the negotiated tier on a stated sample per build, and the mechanical cycles on a stated sample. Naming the sample sizes is what allows two cable assembly quotations to be compared, because the test scope is the line that differs most between them.
Step four: book the tool against the sample date
The two are scheduled together.
Cutting the production tool before the moulded sample is approved removes the only opportunity to correct the envelope at no cost. A programme that books the sample and the tool in the same window treats the sample as the gate rather than as a formality.
Where cable assembly programmes lose time
Three patterns, and the third is the most avoidable.
A drawing that omits the moulding, an identification component added after the connector tool is cut, and a test scope agreed verbally and priced differently in two quotations. Each sits in the first two weeks of the programme rather than the last.
FAQ
Should the tooling include the test fixture?
It should be quoted, and it is often omitted because the tool is visible in the sample and the fixture is not. The fixture holds the assembly during measurement, so a quotation without it describes the product and not the process, which is why the two lines are requested separately.
How much does the identification component add to the unit price?
A component and one soldering step in the connector assembly, which is a small addition to a cable’s unit cost. The larger effect is on the tooling and the test, because a connector that carries a component needs its own assembly sequence and a test that confirms the negotiated tier.
What sample size is reasonable for the mechanical test?
Enough to produce a series rather than a single figure, which in practice means a handful per build rather than one unit. The result is recorded with the build it came from, and a change to the connector, the moulding or the jacket is treated as a new build for that test.
Can a cable assembly programme start without a moulded sample?
It can, and the tool is then cut against the drawing alone, which is where envelope problems are discovered at the modification stage. Where the schedule genuinely cannot accommodate a sample, the drawing carries the moulding dimensions explicitly so that the tool maker is working to a stated envelope.
Next step
Send the connector, the length, the tier and the volume to Wecent Group through the contact page. The reply sets out the four cost lines with the tooling and the test scope itemised. Related reading: charger manufacturing services, OEM and ODM charger manufacturing and inside the charger factory. External references: USB Implementers Forum charger specification, USB-IF compliance programme, IEC standards, BSI standards, Intertek testing services and TUV testing and certification.
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