1.3 BOM, Subassemblies & Kitting

MaterialEffective readinessmanagement of the Bill of Materials (BOM), sub-assemblies, and kitting is the hiddenmost enginecritical logistical mandate in Box Build manufacturing. Due to the high diversity of predictablemechanical boxcomponents build.(screws, Abrackets, designgaskets) only becomes manufacturable onceand the BOMcomplexity isof reshapedtolerance intostacking, testederrors subassembliesin material flow — such as a missing fastener or a wrong screw length — can halt an entire assembly line. This process must ensure the right parts are delivered to the assembler at the right time 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.sequence.

1.3.1 EBOMBOM →Management MBOM:for makeBox the product buildableBuild

The Box Build BOM is fundamentally different and more challenging to manage than a PCBA BOM. It integrates three distinct categories of material.

A) Material Categorization

1. EBOMPCBA (engineering BOM):Sub-Assemblies: “whatFinished itPrinted is”Circuit —Board partsAssemblies on(PCBAs) drawings.from upstream processes. These require serial number scanning for traceability.
2. MBOMCOTS (manufacturing BOM):Components: “howCommercial weOff-the-Shelf buildparts it”like —fans, power supplies (PSUs), hard drives, and displays. These carry their own warranties and compliance certifications.
3. Mechanical/Hardware: The most volatile category, including the enclosure, brackets, labels, gaskets, and fasteners (screws, nuts, washers). modulesMandate:, Mechanical parts must be managed with the same rigor as electronic components due to the high risk of Foreign Object Debris (FOD).

B) Documentation Mandate

The BOM must specify not just the part number, but the kits,required 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 groupsquantity and program images as pseudo-items (so kitting can verify them exist before start).
• Keepthe variantusage 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 = Variantlocation (e.g., A=Blue,"M3 B=Orange)x 6 mm, Qty 4, for mounting PSU to Chassis Floor"). This reduces assembly error.

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1.3.52 MaterialSub-Assemblies readinessand gates (no kit, no start)Modularity

TheComplex lineBox startsBuilds onlyrely whenon pre-assembling smaller units offline before final integration into the chassis. This approach improves efficiency, quality, and cycle time.

A) The Purpose of Sub-Assemblies

• kitParallel passesProcessing: these:
  Allows
  1. Varianthigh-volume 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 presenttasks (e.g., someloading gaskets/adhesives),components onto a fan tray, mounting a display panel) to occur simultaneously, shortening the final assembly cycle time.
  2. windowQuality openControl Gate: andEach noted.sub-assembly can be functionally tested or dimensionally verified before being mounted into the larger system. This ensures a failure is caught early when the cost of rework is low.

  Fail any →

• NG-QUARStandardization: theCreates cart;interchangeable domodules. notIf “borrow”a partssub-assembly adfails hoc.final test, it can be quickly swapped out, minimizing system downtime.

B)

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Manufacturing

1.3.6 Shortage playbook (calm, visible, reversible)

Ladder (in order):

Flow

1. Use AVL alternateSource: (sameRaw spec)parts —and MESlower-level swap with reason code.PCBAs.
2. VariantSub-Assembly swapWorkstation: (ifSpecialized safe): run SKU B while A is short—product wheel helps.
3. Partial buildstation to abuild cleanthe hold pointmodule (e.g., up"Front toPanel 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 scanModule").
• LanguageIntermediate manualsInventory:: SKU-bound;Completed, noserialized freesub-assemblies picking.are placed into inventory.
  

Final Box Build: The final assembly uses the completed sub-assembly module as a single SKU.

1.3.3 Kitting: The Logistics Solution

Kitting

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is

1.3.8the Datalogistical thatprocess bindsof itgathering all (genealogycomponents thatrequired matters)

for

Binda subassemblysingle SNsassembly task or a complete product and delivering them to the assembly workstation in one defined container (the kit). Kitting is mandatory for high-mix, low-volume Box Build lines to control inventory and minimize downtime.

A) Types of Kitting

1. finalFull unitProduct SNKit: atContains install:
   every
   • PSUscrew, traylabel, SN,cable, fanand wallPCBA SN,required harnessto SN(s).build one complete unit.
   • LotOperation IDs: labels, gaskets, TIMs, threadlock, adhesives.
   • Torque record: sampled results per mapKit (stationTask logger)Kit): Contains only the components needed for a single, sequential task (e.g., "The Fastener Kit for Phase 2: PSU Installation").
   • Programming image checksum + time.
     

   This is yourpreferred on high-volume lines as it reduces clutter and material exposure.box-build

genealogy—gold

B) forKitting RMAs.

Quality

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1.3.9 Metrics that tell you kitting works

Mandates

• KitFOD accuracyControl: =Hardware (kitsscrews, startednuts, withwashers) must be bagged or packaged to the exact quantity required. Loose hardware in the kit container is a source of zero line-side adds) ≥ 98–99%.
• Start-on-timeFOD raterisk per shift.
• Pick errors PPM (wrong part in kit).
• Module FPY (L1) — if low,on the lineassembly will starve.line.
• Shortage minutesManagement: The kitting process is the last checkpoint to prevent line-down situations. The kitting technician must audit the kit against the BOM, signing off on quantity verification before release.
• ESD Protection: ESD-sensitive components (bottleneckPCBs, starved)memory trendingmodules) down.must remain in protective packaging (ESD bags or trays) until the moment of installation at the ESD-safe workstation.

Final

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1.3.10 Common traps → smallest reliable fixChecklist

TrapMandate	SymptomCriteria	FixVerification Action
BOM Categorization	EBOMMechanical handedhardware, toCOTS, floorand PCBAs managed in distinct groups.	EndlessAssembly hunting	Builddrawing links each part number to a MBOMUsage Location withwithin modules/consumables;the publish in MESchassis.
Sub-Assembly Mandate	RawComplex screwsmodules bybuilt lengthand onlyverified offline before final installation.	WrongSub-assemblies torque/hardware	Torquecarry groups:their colorown cupsserial +number PNand +quality N·m on cartsign-off.
Kitting Accuracy	LabelsHardware free-picked(screws, washers) packaged to exact quantity required per task.	RegionKitting mix-upstechnician performs a	Label100% kitsquantity audit peragainst SKUthe +BOM MESbefore print;releasing block start withoutthe kit to the floor.
ESD Integrity	TIMsESD-sensitive asitems “shopremain supply”in protective packaging until installation.	Over/underAudit paste	TIMensures ESD bags are included in the kit withand beadproperly gaugeshandled &at photothe map; lot/expiry scanworkstation.
FOD Prevention	ModulesLoose withoutfasteners testare eliminated from the kitting process.	ReworkOnly atbagged/taped hardware is delivered, preventing misplaced screws in the 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 borrowunit.

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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.