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1.2 Typical Products & Complexity Levels

Complexity in box build is less about how many parts sit on a BOM and more about how tightly mechanics, wiring, software, and compliance interact. Each added requirement—whether sealing against water, loading secure keys, or managing airflow—reshapes the way a line must be designed and staffed. By breaking products into practical levels of effort, factories gain a shared framework that aligns design intent with manufacturing reality, making risks and resource needs visible before they disrupt schedules.

1.2.1 What actually drives “complexity”

Not just part count. It’s a blend of:

  • Assembly density (standoffs, fasteners, torque points, adhesives).
  • Interconnect (harness count/length, shield bonds, RF).
  • Software (programming, keys, calibration, variant options).
  • Regulatory (earth/hipot/leakage, EMC gaskets, IP seals).
  • Thermals & mechanics (TIMs, fans, airflow, tight cosmetics).
  • Variant spread (SKUs, regional labels, accessories).

Use these as dials when scoping a new box.


1.2.2 Five levels you’ll actually see (with examples)

Level

Typical product

What makes it simple/hard

Tester needed

Setup you want

L1 – Simple control unit

Small controller, sensor hub, wall thermostat

1–2 PCBAs, few fasteners, 1 harness or none, light labels

Continuity/power-on, basic I/O

Single bench or U-cell; paper SWI → later MES

L2 – Modular panel

DIN-rail panel, PSU tray, fan wall

Multiple subassemblies, torque map, 3–6 harnesses, earth test

Functional with loads, earth continuity

Small flow line; torque tools w/ presets; routing map

L3 – Connected device

Gateway, HMI, NVR, set-top

Programming, keys/MACs, storage, antennas, thermal pads

Scripted FCT, network check, soak

Fixtures for alignment, label station from MES, thermal/TIM kit

L4 – Rugged/IP system

Outdoor node, vehicle controller

Gaskets, 360° shield bonds, IP67 seals, heat spreaders

FCT + hipot/leakage, IP spray/dunk

Seal stations, gasket compression checks, 100% visual gates

L5 – High-end/rack system

1–4U server, cabinet/kiosk

Many modules, airflow management, variant kits, safety

Full FCT, burn-in, safety (earth/leakage), network

Conveyor/cell hybrid, kitting supermarket, serialized accessories

If it ships to the field solo and takes a screwdriver to open, it’s at least L2–L3.


1.2.3 Effort by level (what to plan for)

Area

L1

L2

L3

L4

L5

Steps/unit

10–25

25–60

60–100

80–140

120–250

Torque points

2–6

6–20

10–30

20–40

40+

Harness touchpoints

0–2

3–8

5–12

8–15

15+

Programming ops

0

0–1

1–3

1–3

2–6

Safety tests

Rare

Earth

Earth

Earth + Hipot/Leakage

Earth + Hipot/Leakage

Cosmetic sensitivity

Low

Med

High

High (seals)

Very high (front panels)

Pack complexity

Low

Med

High

High

Very high (accessories/rails)

Numbers are guidance—use your BOM and test plan to size the cell.


1.2.4 Complexity scorecard (10-minute estimate)

Give each item 0–2 points; sum for a rough Complexity Score.

  • PCBAs ≥3 (1), ≥5 (2)
  • Harness interfaces ≥6 (1), ≥10 (2)
  • Programming/keys ≥1 (1), secure/provisioning (2)
  • Gaskets/IP seals present (1), IP67/69K (2)
  • Earth/hipot/leakage (1), plus RF/antenna tuning (2)
  • TIMs: pads only (1), paste/shims map (2)
  • Variant options ≥3 (1), ≥6 (2)
  • Cosmetic grade B (1), grade A/retail (2)

Score → Level (rule of thumb)

0–3 → L1, 4–6 → L2, 7–9 → L3, 10–12 → L4, 13+ → L5.

Use this to pick fixtures, staffing, and test depth.


1.2.5 Risks & first fixes by level

  • L1: Risk: complacency (wrong labels, loose standoffs). Fix: one-page torque/label check; single fixture for alignment.
  • L2: Risk: stripped threads/grounding misses. Fix: torque audit per shift; earth bond tile; star washer callouts.
  • L3: Risk: key/memory mix-ups, thermals. Fix: scan-to-program, checksum verify; TIM kit with photo map; 5-min thermal sanity soak.
  • L4: Risk: leaky seals and long shield pigtails. Fix: gasket compression gage; 360° backshells; IP spray sample per lot.
  • L5: Risk: variant chaos and airflow mistakes. Fix: SKU scan unlocks SWI/labels; airflow arrows & tape-out in chassis; burn-in matrix.


1.2.6 Staffing & line design patterns

  • L1: 1–2 operators, one bench, torque driver + small tester.
  • L2: 2–4 operators in U-cell; kitting cart; torque tools with presets; quick routing fixtures.
  • L3: 3–6 operators; two fixtures (mech + test) in ping-pong; label/program station tied to MES; small burn-in rack.
  • L4: 4–8 operators; seal station, leak/IP fixture; E-stop & hipot cage; dedicated visual gate.
  • L5: Cell + conveyor; feeder lines for subassemblies; ICT/FCT + burn-in bays; pack cell with accessory supermarket.


1.2.7 When to upgrade the process

  • Change from L2→L3 when: programming & calibration show up, or test >5 min. → Add MES recipe push, image vault, and soak.
  • L3→L4 when: IP claims or safety testing appears. → Add gasket gauges, hipot cage, 100% shield/earth checks.
  • L4→L5 when: rack/cabinet scale or >6 variants. → Add product wheel, accessory kitting, separate pack line.


1.2.8 Example mapping (three real-world flavors)

  • Wall thermostat (L1→L2): snap-fit enclosure, 4 screws, one ribbon. Key risks: wrong faceplate label, cracked standoffs. Fixtures: bezel locator, torque driver 0.4–0.6 N·m.
  • Outdoor gateway (L3→L4): PCBAs + LTE modem, GPS, IP67 gland, shielded harness. Risks: gasket nicks, antenna mis-seat. Needs: 360° shield clamp, IP spray, GNSS lock test, 700–1000 VDC hipot to chassis.
  • 2U network appliance (L5): hot-swap fans/drives, rails, airflow baffles, dual PSUs. Risks: reversed fans, missing EMI fingers, thermal pads mis-placed. Needs: torque map, airflow verification, 30–60 min burn-in, label/IMEI/MAC control.


1.2.9 Pocket checklist — scoping a new box build

  • Count PCBAs/harness interfaces; assign a level (L1–L5) with the scorecard
  • Identify tests: function, earth/hipot, IP, burn-in; estimate durations
  • Note seals/TIMs and airflow features; plan gauges/fixtures
  • Confirm programming/keys flow; tie to MES and label set by SKU scan
  • Choose line pattern (bench/U-cell/conveyor) and staffing
  • Define acceptance: torque, cosmetics, label map; first-article plan



Conclusion: Assigning a clear complexity level and matching it with the right fixtures, tests, and staffing keeps box builds efficient and repeatable. With this structured approach, even the most demanding systems can be assembled with consistency and confidence.

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