Can one Case Assembly Workstation handle both batch sizes?

Answer: It can, but not in one shift without cost. Twelve changeovers in the morning and a 95-second cycle in the afternoon fight over the same bench.

Is a 28-minute changeover acceptable for small batches?

Answer: No. A sequenced trolley, two clamps and quick fittings bring it to 12 minutes. Going lower means a new fixture, which pays back less than a solid first-off.

Do written instructions really control ESD habits?

Answer: They control the order, which is most of the risk. Grounding before touching the case, verified by a strap test each shift, makes static failures traceable.

What should a field bay fix first?

Answer: Levelling. A 20 mm ground step puts the latch 2 mm out, and four adjustable feet beat any precision fixture.

18 Units vs 260 a Day: Case Assembly Workstation Actions

Quick answer: Small custom batches and high-volume lines need different actions. Eighteen units a shift turn on changeover and first-off checks; 260 a day turn on poka-yoke.

Three industries, three sets of actions
Small batches: changeover and first-off
High-volume line: cycle and poka-yoke
ESD and cleanroom hand movements
Mobile bay at a field repair point
Four rework locations and their limits
FAQ

1. Three industries, three sets of actions

The same bench assembles an ammunition case and an electronics case with different hands. One presses a gasket and threads a seal wire dozens of times a shift; the other aligns a panel through a 3 mm gap.

Duty	Size and main actions	Common mistake
Ammunition	640 × 420 × 260 mm, 3 mm wall; liner, gasket, seal wire	Gasket out of groove
Electronics	480 × 360 × 180 mm; conductive gasket, panel, inserts	Strap ungrounded, ESD
Instruments	520 × 380 × 240 mm cavity; damping pads, levelling	Pad pinched, lid binds
Field repair	800 × 500 × 340 mm, 21 kg; module swap, latch reset	Latch opens on the lift

Handling splits three ways: carry, lift, hand over. A 21 kg case exceeds a comfortable one-person hold, so anything heavier goes to two people. Set the bench for the heaviest case and raise light ones on a platform.

Tooling changes too: a roller presses the gasket, an air driver closes latches at 2.8 N·m, electronics inserts accept 0.8 N·m. Lowering air pressure does not convert one driver into the other; the head changes.

2. Small batches: changeover and first-off

At 18 units a batch, changeovers outnumber assemblies. Twelve changeovers a shift at 28 minutes each consume 5.6 hours.

Case Assembly Workstation: a frosted case rests on its side, lid edge forming one white line, black hinge blocks at both ends

A 420-second unit is normal at that volume. Slow cycles are tolerable; a skipped first-off is not. Build 3 first-off units: one to keep, one torn down for latch witness marks, one for a leak test.

Item	18 units	260 units
Changeovers	12 per shift	1 per shift
Unit time	420 seconds	95 seconds
Gate	3 first-off units	Latch-present sensor

Mistakes cluster right after the first-off. The operator sees a good unit, speeds up, misses gasket compression on unit four, and trims a liner 5 mm short by unit six. Training does not fix that; a switch that lights only when the clamp is fully down does.

Changeover has removable steps. Order the trolley by job sequence, hold the fixture with two eccentric clamps, use quick-disconnect fittings. Those three take 28 minutes to 12.

3. High-volume line: cycle and poka-yoke

At 260 units a day the cycle falls to 95 seconds. The bay stops assembling and starts preventing: a missed part becomes impossible rather than memorable.

Latches are the usual omission. A proximity switch that confirms the latch is seated keeps the conveyor from releasing an open case; visual inspection leaves roughly 1.8 per thousand, the sensor brings it under 0.1.

Torque needs a record. Fit the driver with a transducer, four screws per case, and stop the line on an out-of-range reading. At 260 cases and 1040 screws a day, sampling covers 3% at best.

Fast lines hide one more defect: a liner fitted upside down. EVA liners differ by 2 mm between faces, and a reversed liner still closes. A red pull tab on the back face makes it visible at a glance.

4. ESD and cleanroom hand movements

In an electronics bay the movements follow static rules. Bench resistance sits between 10⁶ and 10⁹ ohms, humidity between 45% and 60%, temperature at 22℃ plus or minus 3℃, illumination at 600 lux.

Case Assembly Workstation: a clear case lies open, lid upright behind it, two black latches at the lid corners, black cavity on a marble bench

Parameter	Range	Consequence of drift
Surface resistance	10⁶ to 10⁹ ohms	Charge drains slowly onto panels
Humidity	45% to 60%	Below 40% charging worsens
Illumination	600 lux	Below 500 lux a gasket fault hides

Ground first, then touch the case. Keep the liner 100 mm off the bench rather than laying it down. Hold panels by the edges only.

Failures concentrate on the first habit. A wrist strap clipped to a sleeve instead of skin reads above 10⁹ ohms, which equals wearing nothing. Test against a 1 megohm reference each shift.

One movement gets skipped: peeling the film. Do it while grounded, because the peel can generate 2000 volts, enough to destroy a 3 mm MOS device.

5. Mobile bay at a field repair point

A field repair point has no workshop, so the bay folds into a van. Unfolded it takes 6 square metres; two people erect it in 12 minutes and pack it in 8.

Power comes from a 5 kW petrol generator, and air tools give way to manual wrenches. At -15℃ air lines ice up and battery capacity drops 40%.

The typical failure is an unlevelled bench. Field ground varies 20 mm, the case sits tilted, and the latch lands 2 mm off; forced closure breaks the tongue. Four adjustable feet cost 3 minutes.

Coastal sites at 240 hours of salt spray add one habit: wipe the bench dry and oil the hinges before packing up.

6. Four rework locations and their limits

Rework is sorted by location, not by process. The same latch fault can come from a tall liner, a distorted case, or a latch never pressed home.

Location	Limit	Action
Latch	Gap above 0.5 mm	Check liner, then flatness
Gasket	Compression below 25%	Replace the strip
Liner	Edge over 3 mm from wall	Recut, never shim
Label	Position off by 1 mm	Peel, clean, reapply

Together those four sit near 4.2% rework at 26 yuan a unit. Getting under 1% does not need more inspectors; it needs the limits at the bench and a 25% sample block.

Log the location too. Five reworks in the same place over three days is a Case Assembly Workstation or material problem, and the line should stop.

Conclusion

Batch size sets the actions and duty sets the hands. Eighteen units need changeover discipline and a real first-off; 260 a day need poka-yoke and torque records; an ESD room needs grounding; a field point needs levelling. A Case Assembly Workstation earns its keep in those movements.

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.