Packaging and kitting for assemblies: damage, presentation and cost

Packaging is a cost line, not a free service

A supplier quote often includes a line called packing, or it does not mention packing at all. Either way, the cost exists: the bag, the tray, the carton, the label, the labour to pack, the space in the container and the disposal at the other end.

For a small assembly, the pack can be a material cost of a few pence. For a large or fragile assembly, it can be a significant share of the delivered price, especially when the pack is bulky and the freight is charged on volume. A pack that protects perfectly but doubles the carton size is not free.

The buyer should see the pack in the quote and in the freight calculation. Ask for the carton dimensions, the quantity per carton, the carton weight and the pallet pattern. Those four numbers explain most of the freight and a good deal of the handling cost.

What actually gets damaged

An assembly usually fails at its most vulnerable feature. A cable can kink at the entry, a connector can be crushed, a terminal can bend, a housing can crack at a thin wall, and a label can be scuffed until it cannot be read. The body of the part is often the strongest element in the pack.

Abrasion is common when parts move against each other. A bag alone does not stop movement inside a carton. A tray with a shaped pocket, a divider or a clip strip does. The pack should hold the part so the vulnerable feature is not in contact with the carton or another part.

Crush comes from stacking. A carton that is strong enough on its own can still fail at the bottom of a pallet if the load is high or the warehouse stacks it badly. The pack needs a stated stack limit and a pallet pattern that respects it.

Moisture and static are invisible risks. A moulded housing may be unaffected by damp, but a label, an adhesive or a metal contact may not. An electronic assembly may need a static shielding bag and a defined handling procedure. If the part is sensitive, the pack is part of the specification, not a purchasing choice.

Bulk, kit or sequence

Bulk supply is the simplest. The supplier packs a quantity of one part number, and the line takes what it needs. It is cheap to pack and easy to count, but it puts the picking and the matching on your line.

A kit packs the parts for one assembly together. The line receives a bag or a tray with everything needed, and the operator does not pick. Kitting reduces line-side space and picking errors, but it adds packing labour, and a single missing part stops the whole kit.

A sequenced kit goes further. The parts arrive in the order of use, or in a sequence that matches the build order. It reduces the operator's decisions to almost nothing, but it needs a stable build sequence, a reliable forecast and a supplier who can pack to it. A change in the build order can leave a sequenced kit unusable.

A sub-assembly kit is a hybrid. The supplier assembles the difficult joint and packs the variant parts loose, so the line chooses the variant late. It keeps the supplier's volume high and the finished goods low, at the cost of a more complex pack and a longer line-side instruction.

Line-side presentation and ergonomics

A pack that is fine in the warehouse can be wrong at the line. The container has to fit the station, the operator has to reach the parts without stretching or bending, and the empty pack has to leave without blocking the aisle.

Weight matters. A carton that is comfortable to lift once is not comfortable to lift forty times an hour. Keep the unit weight within the handling limit agreed with the line, and split a heavy pack into smaller units even if it costs a little more.

Presentation should make the right part easy to take and the wrong part hard to take. A cut-out that exposes one part at a time, a gravity feed rack or a two-bin system with a clear empty signal all reduce picking errors. A deep box of loose parts invites the operator to grab a handful and sort them at the station.

The empty pack is part of the flow. Single-use packaging has to be collapsed and removed; returnable packaging has to be returned, cleaned and stored. Both need space and a process. A returnable system that nobody collects becomes a pile of empty totes in the corner.

The packaging options

The table sets out the common options and where each one fits. Most programmes use more than one, depending on the part and the route.

Modelling the packaging cost

Build the cost from five lines: the pack material, the packing labour, the freight volume, the damage rate and the disposal or return cost. A cheap bag with a high damage rate can cost more than a tray that prevents the damage.

Freight volume is the line most often missed. A tray that nests can cut the carton size and the pallet count. A pack that cannot nest ships air. Ask for the carton and pallet dimensions, then calculate the freight per unit rather than per carton.

Damage cost includes the part, the labour to replace it, the delay and the customer impact. A 1 per cent damage rate on a low value part may be acceptable; on a high value assembly it may justify a much better pack. Use your own history, not a generic rate.

Disposal and return are real costs. Single-use packaging has a waste cost and, in some markets, an extended producer responsibility obligation. Returnable packaging has a cleaning, storage and transport cost. Neither is free, and the cheaper option depends on the loop length.

Validate the pack with a real shipment

A drop test on a sample box is a useful screen, but it does not reproduce a pallet that is stacked badly, a courier who throws the carton or a ship that rolls for three weeks. Test to a recognised schedule for the route, then send a trial shipment and inspect what arrives.

Open the trial at the destination, not at your own warehouse. Check the parts, the labels, the seals and the pack itself. Photograph the condition on arrival and compare it with the dispatch photos. A pack that looks fine but has transferred a shock to the connector is still a failure.

Include the line in the review. The operator who opens the pack every day will tell you what binds, what spills and what takes too long. A five minute trial at the station is worth more than a specification written in an office.

Finally, write the pack into the drawing pack or the purchase specification. The material, the dimensions, the quantity per pack, the label and the pallet pattern should all be controlled. A pack that is left to the supplier's discretion will change when the supplier changes.