Coiling, Bagging and Cartoning Cable Assemblies for Export Without Damage

Packing cable assemblies for export is the last process step and the first one buyers stop specifying. The assembly passes continuity, passes withstand-voltage, gets coiled by hand, gets a tie pulled tight around it, goes into a bag, goes into a carton, and then spends five weeks in a steel box that swings, heats up past anything the shop floor ever sees, and cools down again every night. A harness that left the test bench good can arrive kinked, set, cracked at a strain relief or with a bent terminal — and none of that shows up on the test record you were sent.

The fix is a packing specification written as a revision-controlled document, not a sentence in an email. Here is what belongs in it, in the order the goods move.

What actually breaks between the packing bench and your dock

Five failure modes account for most harness arrival damage, and each has a specific cause in the packing method.

• Permanent set in the jacket. The cable holds the shape it was packed in, or holds a groove where a tie was. It never comes out.
• Bend-radius damage at the coil. A coil tighter than the cable was designed for deforms the shield, migrates the conductor within the jacket, or strains the insulation wall unevenly — invisible on inspection, visible on a withstand-voltage retest.
• Point loading on connector housings. A loose assembly at the bottom of a carton with fourteen kilos above it takes that load through the hardest object in the bag, which is the housing.
• Terminal damage on unterminated ends. Loose crimped terminals with no housing dangle, catch, and bend. A bent tine on a receptacle terminal is scrap.
• Moisture, salt and the slow stuff. Container humidity cycles daily. Bare copper tarnishes, printed labels lift, cartons soften and lose stacking strength.

Two more apply to a subset of assemblies: electrostatic damage on anything with a semiconductor at one end, and traceability loss — goods arrive fine but nobody can say which lot they came from, which is a failure of exactly the same kind as a bent pin.

The coil: bend radius, twist and the tie that leaves a groove

Coiling looks like the least technical operation on the floor. It causes more arrival damage than any other.

Radius, and the mistake everyone makes with the number

Every cable has a minimum bend radius on its datasheet, expressed as a multiple of the outside diameter. As a working orientation, fixed installation is commonly in the region of four to six times OD, repeated flexing higher again, and continuous-flex or torsion service — drag chain, robot dress packs — higher still. Those are orientation figures. The binding number is on the datasheet for the cable you actually bought, and if the datasheet is silent, that is itself a finding about the cable.

The mistake is a units error, and it is extremely common: the datasheet gives a radius, the packing bench measures a coil diameter. A coil formed at the minimum bend radius is half the size it should be. Write the requirement into your specification as a minimum coil diameter — at least twice the minimum bend radius, and comfortably more where you can afford the carton volume — so nobody has to do the conversion at 5pm on a shipping day.

Twist, and why a figure-eight is not a preference

Winding cable into a simple circular coil puts one full turn of twist into the cable per loop. On a length of single-core wire nothing much happens. On a shielded twisted-pair, a servo feedback cable or anything with a foil-and-braid construction, accumulated twist distorts the lay of the pairs and the shield coverage, and it will not fully unwind when the customer pulls the coil out. Figure-eight coiling reverses the twist on alternate loops so it cancels. For any shielded or paired assembly over a couple of metres, specify figure-eight and say why — the construction detail that makes this matter is covered in servo and encoder feedback cable shielding.

Why a tight tie leaves a permanent mark

Cable jackets — PVC, TPE, polyurethane — are viscoelastic. Put a jacket under sustained compressive strain and the polymer chains gradually rearrange to accommodate it; the deformation stops being elastic and becomes permanent. Now add the container: interior temperatures over a summer sailing routinely run far above the shop floor, and every ten degrees accelerates that relaxation. A nylon tie tensioned by a pistol tool with a cut-off head is applied at a force chosen to make the tie hold, not to protect the jacket. Five weeks at temperature later, the groove is a feature of the cable.

That groove is not cosmetic. It is a local reduction in insulation wall thickness, which is where a withstand-voltage test wants to fail — the reason the outgoing hipot record and the incoming inspection can disagree is often sitting right there. On a shielded cable it also deforms the braid and shifts the geometry that sets impedance. The reading of those test records is set out in continuity, hipot and insulation resistance.

So write the tie rule explicitly: hook-and-loop straps or wide flat ties, hand-tensioned, no pistol tool with an automatic tension setting; no tie across a connector body; no tie at the strain-relief transition, which is the single highest-stress point on the assembly; and an acceptance criterion the inspector can apply — no visible indentation in the jacket when the tie is cut.

Bagging: static, moisture and the connector face

Three separate jobs get done by a bag, and buyers routinely specify one bag and expect three outcomes.

Static. Three material families get called "antistatic" and they do different things. Low-charging pink polyethylene resists triboelectric charge generation but provides no shielding. Conductive black bags dissipate but are not a barrier in the general case. Metallised static-shielding bags act as a Faraday enclosure and are the only family that protects contents from an external field. A bare passive harness with no semiconductor anywhere on it often needs none of them; an assembly with an over-moulded electronics module, or one going into a customer's ESD-controlled receiving line that will reject non-conforming packaging on sight, needs the right one named by type. Specify the family and the standard reference, not the word "antistatic".

Moisture. Desiccant only does anything inside a moisture-barrier bag. A sachet dropped into a vented polyethylene bag is theatre — it saturates in days and then sits there. If moisture matters for your route and season, specify a barrier bag, a desiccant quantity sized to the bag's surface area, a heat seal, and a humidity indicator card so that the person opening it can tell whether the barrier held.

Mechanical protection of the interface. Mating faces want caps or plugs, or at minimum an individual bag. Unterminated crimped ends want to be bundled and taped together, or supported in a foam-lined tray, so no single terminal takes a load. Decide individual bagging versus bulk bagging deliberately: individual costs more per piece and prevents connector-on-connector abrasion, and it is also what lets you put a lot-code label on every unit.

Cartons, labels and lot codes

Board grade, not "strong carton"

A carton is specified by board construction and a strength figure — edge crush or burst, single-wall or double-wall — not by adjective. Two facts should drive the number. Cartons in a container carry the compressive load of everything stacked above them, so the spec follows the stack plan rather than the single carton. And corrugated board loses a substantial share of its stacking strength as it takes up moisture, so a carton that is adequate in a dry warehouse can be inadequate after four weeks at sea. Specify board grade, maximum gross weight per outer — keeping it inside comfortable manual-handling limits is worth doing for your own receiving team — inner cartons or dividers so assemblies cannot migrate, void fill, and corner protection where the stack plan concentrates load.

What the label has to carry

The carton label is a data record, and every missing field becomes somebody's phone call.

The detail that separates a specification from a wish is where the lot code lives. Put it on the unit or on the inner bag, not only on the outer carton. The moment a third-party warehouse de-cartons your goods into bins, a carton-only lot code is gone, and with it any ability to isolate a bad reel of wire to the units that contain it. Ask for a label on every inner bag, or a laser or ink-jet mark on the jacket where the assembly allows it. And ask what the lot code actually resolves to on the supplier's side: a code that only encodes a packing date is decoration. A useful one ties back to the wire reel, the terminal lot, the press and applicator, and the shift.

Who owns the damage when packing fails

Two contractual points decide whether a damaged container is your problem or somebody else's. Under Incoterms 2020, risk under FOB passes when the goods are on board the vessel — but a container is stuffed at a yard days earlier, which means damage during the interval that matters most is hard to attribute in practice. For containerised cargo, FCA is the term drafted for the way the goods actually move; the comparison is worked through in DDP versus FOB for China shipments, and the container-level mechanics in the CMH guide to FCL and LCL sea freight.

The second point is harsher. Marine cargo policies conventionally exclude loss caused by insufficiency or unsuitability of packing. If your harnesses arrive kinked because the coil was too tight, that is a packing failure, and the underwriter's position will be that it is not an insured peril. The packing specification is the document that moves that risk back onto the supplier, so make it an annex to the purchase order with a revision number, and make conformance to it an inspection point — the pre-shipment inspection scope described in product inspection before shipment should include the packed carton, opened, against your annex.

Common questions

Do I need ESD packaging for a plain wire harness?

Usually not, if there is no semiconductor anywhere on the assembly and your own receiving line has no ESD-controlled area. Where it does become necessary is on assemblies with an over-moulded module or a terminated device, and on any part number going into a customer's ESD-controlled process, which will reject non-conforming packaging regardless of whether the part is sensitive. Decide per part number, write the bag family into the specification, and do not pay for shielding bags across a whole order because one SKU needs them.

How do I stop the factory changing the packing after the first shipment?

Give the packing method a document number and a revision, attach it to the purchase order, and require photographs of a packed and unpacked carton at first article and at every revision. Packing drifts because it is nobody's controlled process; the moment it has a revision number and an inspection point, it stops drifting. Approve the first carton the same way you approve a first article.

Should I ask for vacuum packing or shrink wrap on harnesses?

Rarely, and think it through before you do. Shrink film pulls tight as it cools and can impose exactly the sustained compressive strain that causes permanent set, particularly across a connector edge. A sealed barrier bag with desiccant handles the moisture case with less mechanical risk. If a supplier proposes shrink wrap as protection, ask what it is protecting against.

What to ask the supplier next

1. The current packing specification as a document — inner bag type and gauge, coil method and coil diameter, tie type, units per bag, bags per inner, inners per outer, carton dimensions and gross weight.
2. The minimum bend radius from the cable maker's datasheet for every cable in the assembly, and confirmation that the packed coil diameter is at least twice it.
3. Which tie is used and how it is tensioned, with a written commitment to no visible jacket indentation after the tie is cut.
4. Whether ESD-safe bagging is available, in which family, and at what cost per piece for the SKUs that need it.
5. Whether a moisture-barrier bag with sized desiccant and an indicator card can be offered for long sea transit, and what it adds.
6. The label artwork, with every field listed above shown on a proof, and confirmation of the barcode symbology your receiving system reads.
7. What the lot code encodes on the supplier's side, whether it appears on the inner bag or the unit as well as the outer, and how long the corresponding production records are retained.
8. Photographs of a packed and an unpacked carton at first article, and packing conformance written into the pre-shipment inspection scope.

Huisheng Electronics is a workable case to put those questions to. Its published range spans braided charging cable pairs, servo and encoder signal cables, multi-branch industrial looms and control-cabinet wiring, vehicle harnesses and high-current energy-storage leads — a mix that spans nearly every packing case in this article, from shielded assemblies that want figure-eight coiling to heavy leads that want the carton weight watched. Its stated commercial terms are a minimum of 1,000 pieces, samples dispatched in 7–10 days and volume at 15–25 days to warehouse, with target markets listed as the US, Canada, the UK, Germany and France. Those are the company's own figures, and its standard inner and outer packing specification, its carton dimensions and units per carton, whether ESD-safe bagging is offered, and its lot-code label format are not published details. Sort the SKU mix against the minimum order first — the arithmetic is in planning a 1,000-piece harness MOQ — then settle the packing annex, then place the order. If the shipment is also crossing a border, the marking and origin fields on that carton label are covered in duty and origin on imported wiring harnesses, and the spec-side standards in ISO 6722 and crimp validation.