1.3 BOM, Subassemblies & Kitting

Material readiness is the hidden engine of predictable box build. A design only becomes manufacturable once the BOM is reshaped into tested subassemblies and operator-friendly kits, with every torque spec, consumable, and variant captured in the right system. When modules are pre-verified and carts are scanned clean, the line can flow without the distractions of shortages, mix-ups, or last-minute fixes.

1.3.1 EBOM → MBOM: make the product buildable

• EBOM (engineering BOM): “what it is” — parts on drawings.
• MBOM (manufacturing BOM): “how we build it” — modules, kits, and consumables grouped for the line.

Convert once, own in MES/ERP

• Break the product into L1 subassemblies (fan wall, PSU tray, front I/O, harness set, label set).
• Add consumables (TIMs, threadlock, adhesives, gaskets, tape, labels) as real MBOM lines with units/kit
• Record torque groups and program images as pseudo-items (so kitting can verify them exist before start).
• Keep variant columns (A/B/C)—same MBOM, different marks.
  

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1.3.2 Module breakdown (build the slow bits off the main line)

A good module saves time on the box line and can be tested alone.

Module (L1)	Contents	Why it helps	Test/Check
PSU tray	PSU, cage, EMI fingers, earth bond	Early torque/earth; easy swap	Earth bond < 0.1 Ω
Fan wall	Fans, guard, harness, label	Cable work off-line; airflow arrows validated	Spin & current
Front I/O	PCBAs, light pipes, buttons, harness	Cosmetic alignment off-line	Button/LED check
Display/door	Hinge, gasket, bezel	Seal & flushness off-line	Gasket compression
Harness set	Pre-tested loom bundle	One SKU, one bag	Continuity log
Label set	Regulatory + brand + SN placeholder	Zero hunting; region-safe	Visual vs map
Accessory kit	Cord, screws, rails, manual	Pack ready; region-safe	Count & region

Rule: If it’s fiddly, has torque, or needs test—make it a module.

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1.3.3 BOM that the floor can pick (columns that matter)

Item	Qty/Unit	Int. PN	Mfr PN	Description	Variant A/B/C	Alt/AVL	Torque/Spec	Notes
10	1	800-110	—	Subassy, PSU Tray	✔/✔/✔	—	Earth <0.1 Ω	L1 module
20	1	520-015	ABC-123	Fan, 80×80, 12 V	✔/—/✔	DEF-456	0.8 N·m	Arrow ↑
30	1	760-042	—	Kit, Labels (EU)	—/✔/—	—	—	Map LB-22
40	1	911-007	—	TIM Kit (pads/paste)	✔/✔/✔	—	Bead 1.5 mm	Syringe 3 g
50	1	600-201	—	SW Image, v3.2	✔/✔/—	—	Checksum 9F…	MES-pushed

Tips

• Put subassemblies in the top 20 lines; raw parts later.
• Use Alt/AVL openly; don’t hide in a PDF.
• Put torque / bead sizes / gasket compression right in BOM notes.

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1.3.4 Kitting patterns (choose one, or blend)

• Full cart kit (one cart = one unit): fastest at line start; great for high mix.
• Module supermarket + light point-of-use pick: keep L1 modules on a min/max supermarket; line picks only a short list (screws, pads, ties).
• Wave kitting: pre-stage N units for a shift; good for runners.

Cart layout (top → bottom)

1. Label bin (locked to SKU), program card, torque map print.
2. L1 modules: trays, fan wall, I/O, harness set.
3. Small parts totes: screws by torque group (color cups), spacers, washers.
4. Consumables: TIM kit, threadlock, tape, gaskets (sealed & dated).
5. Accessories: cords, rails, manuals, region items.

Color bands on the cart = Variant (e.g., A=Blue, B=Orange).

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1.3.5 Material readiness gates (no kit, no start)

The line starts only when the kit passes these:

1. Variant check — Cart barcode = SKU/Variant; MES unlocks SWI, label map, and test only on match.
2. Subassembly status — L1 modules show PASS in MES (with their own SNs/earth test where relevant).
3. Critical-lot scans — PSU, PSU earth strap, harness SN, gaskets, TIMs, adhesives (lot/expiry), labels (region).
4. Torque & tools — Drivers in cal; bits present; torque map printed on the cart.
5. MSD/age-sensitive — None? Great. If present (e.g., some gaskets/adhesives), window open and noted.

Fail any → NG-QUAR the cart; do not “borrow” parts ad hoc.

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1.3.6 Shortage playbook (calm, visible, reversible)

Ladder (in order):

1. Use AVL alternate (same spec) — MES swap with reason code.
2. Variant swap (if safe): run SKU B while A is short—product wheel helps.
3. Partial build to a clean hold point (e.g., up to lid close) — park in WIP-HOLD with red tag & list.
4. Module pull from supermarket — keep the box line moving.
5. Stop — when safety/regulatory items are missing (earth strap, gasket, label set), don’t build.
   

Never substitute safety/EMC pieces without PE/QE sign-off.

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1.3.7 Label & region control (easy to get wrong)

• Label kits per region/SKU in sealed bags with map ID; MES prints SN/regulatory from SKU only.
• Power cords/accessories tied to SKU; pack cell verifies by scan.
• Language manuals: SKU-bound; no free picking.
  

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1.3.8 Data that binds it all (genealogy that matters)

Bind subassembly SNs to the final unit SN at install:

• PSU tray SN, fan wall SN, harness SN(s).
• Lot IDs: labels, gaskets, TIMs, threadlock, adhesives.
• Torque record: sampled results per map (station logger).
• Programming image checksum + time.
  

This is your box-build genealogy—gold for RMAs.

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1.3.9 Metrics that tell you kitting works

• Kit accuracy = (kits started with zero line-side adds) ≥ 98–99%.
• Start-on-time rate per shift.
• Pick errors PPM (wrong part in kit).
• Module FPY (L1) — if low, the line will starve.
• Shortage minutes (bottleneck starved) trending down.

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1.3.10 Common traps → smallest reliable fix

Trap	Symptom	Fix
EBOM handed to floor	Endless hunting	Build a MBOM with modules/consumables; publish in MES
Raw screws by length only	Wrong torque/hardware	Torque groups: color cups + PN + N·m on cart
Labels free-picked	Region mix-ups	Label kits per SKU + MES print; block start without kit
TIMs as “shop supply”	Over/under paste	TIM kit with bead gauges & photo map; lot/expiry scan
Modules without test	Rework at final line	Test L1: earth, spin, LED/button, continuity before box
Quiet alternates	Fire drills at shortage	Put AVL in BOM; enable MES swap with reason
Borrowing from other kits	Ghost shortages later	Block cart close until reconciled; red-tag any borrow

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1.3.11 Pocket checklists

Designing the MBOM

• L1 modules defined; each has a test and a PASS state
• Consumables (TIMs, gaskets, adhesives, threadlock) added as lines
• Torque groups and program image listed as pseudo-items
• Variant columns (A/B/C) filled; AVL alternates set

Building a kit

• Cart scanned to SKU/Variant; MES unlocks SWI/labels/test
• L1 modules show PASS; SNs printed on traveler
• Critical lots scanned (PSU, harness, label set, TIMs/gaskets/adhesives)
• Torque bits present; drivers in cal; torque map on cart

At line start

• Kit OK tile green; no adds; MSD/expiry OK
• First article: dry fit + routing check; torque audit sample
• Bind module SNs to unit SN as installed
  

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Conclusion: Converting EBOMs into tested MBOM modules, enforcing kitting gates, and tying data to MES creates a controlled, traceable build process. With this structure, material handling stops being a source of delays and becomes the foundation for consistent, high-quality output.