Why can't the liner be bonded first in Case Assembly?

Chips and flipping. Later riveting drops dust into foam cells, and further handling lifts the edges.

Is the 5 mm gasket overlap mandatory?

It offsets shrinkage. Less than 5 mm and the joint opens as rubber relaxes; more than 8 mm distorts the seal mark.

What happens when one station exceeds 90 seconds?

The slowest station sets the pace. Split it in two, or move work upstream.

Does Case Assembly always need a moving line?

No. Below 300 cases a day, one operator can build a whole case in a cell.

What balance rate is realistic?

Eighty-five to ninety percent. Below 80 the split is unfair; near 95 there is no slack for an upset.

Case Assembly Line: Hardware, Gasket and Liner Sequence

Quick answer: Case Assembly runs hardware first, gasket second, liner last. Hardware is fixed by impact and torque, so the shell moves under the tool. The gasket seals by compression and cannot survive repeated flipping. The liner is clean and must never meet chips. Split stations along that order and each lands between 45 and 90 seconds.

Dividing the Case Assembly Line into Stations
Why Hardware Comes First
Gasket Seating Order and Overlap
Why the Liner Goes Last
Line Balance and Work in Process Caps
FAQ

1. Dividing the Case Assembly Line into Stations

Case Assembly follows the surface each part touches: hardware on walls and lid, gasket in the rim groove, liner against the cavity. Those postures cannot share one bench without repeated turning.

A mid-size case carries about 416 seconds of direct labour. Across five to eight stations each falls between 45 and 90 seconds. Fewer stations overload one bench; more add handling, and handling brings scuffs.

No.	Operation	Station	Takt (s)
1	Incoming check and kitting	Feed	68
2	Handle, latch and hinge fitting	Hardware A	78
3	Riveting and re-torque	Hardware B	74
4	Rim wipe and gasket seating	Seal	72
5	Lid and base liner bonding	Liner	66
6	Close, latch trial and packing	Final	58

2. Why Hardware Comes First

A rivet gun delivers its blow in under 0.05 seconds and the impulse travels along the wall. A thin panel deflects and the shell creeps 1 to 2 mm across the bench. With a gasket already seated, the lip is squeezed repeatedly and loses rebound within minutes.

Torque tools add a second load: latch and hinge bases pull in opposite directions, so the shell twists and the rim plane drifts. Debris matters too: one chip under the gasket opens a leak no visual check finds.

Reversed order	Immediate effect	Rework cost
Gasket before hardware	Lip flattened, weak rebound	Strip replaced, rim re-cleaned
Liner before riveting	Chips embedded in foam	Liner scrapped, line stopped

3. Gasket Seating Order and Overlap

A gasket starts at a corner, not the middle of a long side. The corner is hardest to press home, and once anchored, both straight runs have a datum. Start in the middle and the strip walks toward both ends, leaving surplus that must be forced in by stretching.

At the return, the tail overlaps the head by 5 mm at the same groove depth, kept off latch bases and hinges. Press with a 20 mm roller at about 100 mm per second and hold stretch below 3 percent, because stretch returns as shrinkage.

4. Why the Liner Goes Last

The liner is the only clean part in the sequence. Egg-crate foam, cut EVA and flocked sheet cannot be wiped free of metal dust, so a contaminated piece is replaced. Running the liner after hardware means chips are already blown off at the pre-final station.

Bonding also ends the flipping. Adhesive peaks within ten minutes, and moving the shell then lets foam slide and lift at the edges. Lid first, base second, cure at 20 to 30 °C. If the lid resists at one corner, the liner is thick and holds the gasket off its seat.

5. Line Balance and Work in Process Caps

A line sized for 600 cases a day runs two shifts of 6.8 effective hours: 48960 seconds, a takt of 82 seconds. The bottleneck sits at 78 seconds, so a stopped rivet gun does not starve the line.

Balance is station time divided by station count times takt: 416 over six times 82 gives 85 percent. Under 80 percent means uneven cutting and someone waiting.

Parameter	Value
Daily output	600 cases
Direct operators	7
First pass yield	96%

Work in process needs a ceiling: two cases between stations, twelve on the line. A larger pile is a blockage, usually at riveting when a gun overheats or at sealing while the operator waits for gasket.

Conclusion

The rule is simple: shock and chips first, compression next, clean parts last. Hardware, gasket, liner. Cut stations along that direction and takt settles between 45 and 90 seconds. Two numbers show whether it is healthy: a balance rate near 85 percent and work in process under twelve cases. Keep both and output becomes predictable, which is what Case Assembly planning is for.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.