Copper, Terminals and Assembly Minutes: What Actually Drives a Harness Quote

Two quotes come back for the same drawing, the same quantity, the same delivery term, and they are 25% apart. Nothing in either document explains why. Both are a single unit price with a minimum quantity beside it, and the buyer is left guessing whether the cheap one has cut something or the expensive one is simply padded.

A wire harness quote cost breakdown is not hard to reconstruct, because a harness is one of the few assemblies where the cost stack is legible from the drawing. Conductor, terminals and connectors, protection and consumables, assembly minutes, test and pack, then overhead and margin. Get a supplier to split those five and the 25% gap will sit in one or two of them — almost never spread evenly across all five.

Copper: the part that moves under you

Start with the conductor, because it is the only line whose price changes while you are deciding.

Copper cost in a lead is arithmetic, and you can do it yourself. Copper's density is 8.96 g/cm³, so a conductor's mass per metre is its cross-sectional area multiplied by that figure. Add roughly 2–5% for lay-up: strands are laid helically, so a metre of finished cable contains slightly more than a metre of each strand.

Multiply the mass by the current copper price, then treat that as the floor. What sits on top of it:

• Tinning. Tin-plated strands cost more than bare copper and are specified for corrosion resistance and solderability. If your drawing does not say, one supplier will quote bare and the other tinned, and there is a chunk of your 25% right there.
• Insulation compound and wall thickness. Thin-wall versus standard-wall changes the material weight and the extrusion cost. Temperature rating and flexibility class change the compound.
• Copper conductivity grade and strand count. A finer strand count for flexibility costs more to draw and to terminate.
• Drum residuals. Wire comes on drums. A job that needs 1.3 drums either leaves a part drum in stock or gets rounded up in the quote. On a short run, that rounding is visible in the unit price.

The commercial question follows directly: is the quote fixed, or indexed? Ask for the quote validity period in days, and ask whether the price carries a copper-index adjustment clause and what threshold triggers it. Both answers are legitimate. A fixed price for 30 days with no clause and a 90-day indexed price are simply different risk allocations, and you should know which one you have bought. On heavy-gauge harnesses this single question moves more money than any negotiation on assembly labour.

Terminals and connectors: usually the biggest surprise

On a low-circuit-count lead with short wire, the terminated ends can cost more than everything else combined. Three things drive that.

Piece price and pack size. Terminals and housings are sold in reels and bags with their own minimum quantities. If a housing comes in packs of 5,000 and you need 1,000 assemblies, someone buys 5,000. Either the factory absorbs it and prices it in, or it appears as a line you did not expect. Ask directly: what is the pack minimum on each purchased part, and what happens to the remainder?

Purchased or consigned. You can send the connectors yourself. Buyers doing this for the first time under-estimate two costs on the factory side — incoming inspection, and the risk of running out mid-build — so most shops apply a handling charge on consigned material. That charge is negotiable and should be visible. What is not negotiable is the schedule risk: if your consigned parts land late, the line stops and your lead time moves, and the factory is entitled to say so. Ask what handling percentage applies to consigned parts, and what the shortage policy is.

Availability. Interconnect parts run on their own supply calendar and can go to long lead times without warning. A quote priced against stock and a quote priced against a 16-week buy are different quotes with the same number on them. Ask which parts on the bill of materials are held in stock and which are bought to order.

None of this is visible unless your enquiry package names the parts precisely. A drawing plus a wire list plus a connector bill of materials with manufacturer part numbers gets you comparable quotes; a photo and a length gets you three numbers you cannot line up. That package is worth building properly — see what belongs in a harness RFQ.

Assembly minutes: where "the same drawing" stops being the same

The third bucket is time, and it is the one where two shops genuinely differ rather than just pricing differently.

Think in operations rather than in hours. A single-ended lead is one cut, one strip, one crimp. Every feature you add to the drawing adds a discrete operation with its own seconds:

• Each additional branch adds a lay-up on the formboard, plus a break-out that has to be positioned and secured.
• Each splice — ultrasonic, crimped or soldered — adds a station and, usually, an insulation step over it.
• Tape wrap is priced by the centimetre. Half-lapped wrap uses roughly twice the tape and twice the time of a spiral wrap over the same length.
• Sleeving and conduit add cut-to-length, feed and end-securing operations.
• Labels and markers add a print step, an apply step and, if you require it, a verification step.
• Heat-shrink, especially adhesive-lined, adds a heat cycle and a cool-down that is hard to parallelise.
• Testing adds bench time per assembly, and the fixture that makes it fast has to exist.

The equipment mix decides how many of those seconds are machine seconds. Automatic cut-strip-crimp units do the repetitive front end at a rate no bench can match, which is why a shop with them will quote a plain two-ended lead lower than one working entirely on benchtop crimpers. Bench work reasserts itself as soon as the assembly needs a formboard. Huisheng Electronics, for instance, publishes an equipment roster listing more than twenty production and test machines, spanning automatic cut-strip-crimp units, servo crimping presses, benchtop crimpers and forming machines — a mix that suits both ends of that split. Where a specific shop sits on it is worth asking about explicitly, because it tells you which of your part numbers they will be competitive on.

Two practical asks. First, request the quote split between machine-processed leads and bench assembly, even approximately. Second, ask for the standard time per assembly the quote is based on. A supplier who cannot state it is quoting from feel, which is fine at 1,000 pieces and dangerous at 50,000.

The full cost stack, and how to reconcile two quotes

Two of those deserve a sentence each, because they are the ones that turn a good unit price into a bad total.

Setup cost per part number. Every distinct assembly needs a formboard laid out, applicators fitted and set, a first article approved. That cost exists whether you order 1,000 or 100,000. At small volumes it is either charged openly as a one-off or buried in the unit price — and if it is buried, splitting an order across more SKUs quietly multiplies it. This is the mechanism behind most of the "why is my MOQ so high" arguments; the reasoning is worked through in planning SKUs around a 1,000-piece minimum.

Test fixtures. A dedicated continuity fixture costs money to build and belongs to whoever paid for it. Settle ownership in the purchase order, not later.

With the stack laid out, reconciling two quotes becomes mechanical. Do it in this order. Stop when the gap closes.

1. Normalise the commercial terms. Same Incoterms 2020 rule, same currency, same payment terms, same quantity break. A price quoted on different terms is not a comparison.
2. Compare the conductor assumptions. Bare or tinned, insulation type and wall, strand class. Ask both suppliers to state them explicitly.
3. Compare the purchased-parts list. Same manufacturer part numbers for housings, terminals and seals, or substitutes? A substitute at half price is a different product, not a discount.
4. Compare protection. Tape type and wrap method, sleeve or conduit, shrink with or without adhesive liner.
5. Compare test scope. Continuity only, or continuity plus insulation and withstand-voltage, and is a record issued per lot?
6. Ask both for setup and tooling as separate lines. Then rebuild the total including them.
7. Ask both for the quote validity period and whether the price is indexed.
8. Compare pack. Coiling and restraint method, inner packaging, carton count and cube.

By step 5 most gaps have resolved into one of three things: a different wire specification, a substituted interconnect part, or a test scope one side left out. The remaining difference is real, and it is the one worth negotiating. The general version of this exercise, across categories, is covered in why China quotes for the same spec differ.

Common questions

Should I ask for a cost breakdown, or is that unreasonable?

Asking for a breakdown into material, purchased parts, labour and setup is normal and most shops will provide it at the level above. Asking for supplier margin, or for their purchase price on each terminal, generally is not — and pushing for it tends to produce a fictional breakdown that adds up to the number they already quoted. Ask for the split that lets you compare two quotes, not the split that lets you audit their business.

At what quantity does the unit price actually improve?

The step changes come from batching, not from goodwill. Setup amortises across the run, wire is bought in whole drums, and purchased parts hit their next pack break. That is why the same shop can quote a materially better price at 5,000 than at 1,000 with no change to the drawing. Stated minimums at this end of the market commonly start around 1,000 pieces per item, with samples dispatched in 7–10 days and volume in 15–25 days — so ask for pricing at your realistic annual volume in three or four call-offs, not at your first order quantity. The negotiation itself is covered in minimum order quantity negotiation.

The cheapest quote came from a company that also has an import-export licence. Does that mean it is a trading company?

Not on its own. Many small Shenzhen electronics companies register a business scope covering both production and import-export, because they manufacture and also export directly. The scope tells you what they are permitted to do, not what they do. Resolve it by looking at the production evidence rather than the licence — and by checking that the entity quoting you is the entity that will invoice you, which is the same discipline as checking a certificate's holder name and validity.

What to ask the supplier next

Attach this to your enquiry and you will get quotes you can actually line up side by side:

• Split the quote into conductor, purchased interconnect parts, other materials, assembly labour, test, and pack.
• State the wire specification you priced: conductor size, bare or tinned, insulation type and wall, strand class.
• List every purchased part by manufacturer part number with its pack minimum, and mark which are stocked and which are bought to order.
• State the quote validity period in days, and whether a copper-index adjustment clause applies and at what threshold.
• Quote setup, applicator tooling and test fixtures as separate one-off lines, and state who owns the tooling and fixtures afterwards.
• Give pricing at three quantities — your first order, your annual volume in one lot, and your annual volume in four call-offs.
• State the Incoterms 2020 rule and give carton dimensions, pieces per carton and gross weight.

Suppliers who build to drawing across several product families are used to this level of enquiry, and the ones who answer it in full are usually the ones who costed the job rather than guessed it. Huisheng Electronics, which runs six wire and harness lines on an OEM and ODM basis and publishes its equipment roster and its stated MOQ, sampling and lead-time figures openly, is a reasonable place to test the list — its stated terms and the caveats attached to them are set out on the Huisheng Electronics factory page. Send the same seven points to every shop you are comparing, and the 25% gap will explain itself. For the costs that sit outside the quote entirely, the hidden costs of sourcing from China is the companion list.