1.3 BOM, Subassemblies & Kitting
Material readiness and module breakdown.
Turning a design into a smoothly built product starts with reshaping the BOM and how materials show up at the line. The handoff is EBOM → MBOM: EBOM (engineering bill of materials) captures “what it is,” while MBOM (manufacturing bill of materials) defines “how we build it” with real modules and kits. Breaking work into small, testable subassemblies keeps the main line fast and predictable, while kitting turns planning into something a cart—and an operator—can trust at start. Control lives in systems too: MES (manufacturing execution system) runs the shop-floor rules, and ERP (enterprise resource planning) holds the business record so variants, labels, and consumables match the SKU. Traceability—serial numbers, lot IDs, torque logs, and software images—creates product genealogy that pays off in RMAs and compliance. With clear alternates via an AVL (approved vendor list) and clean readiness gates, shortages become manageable detours instead of line-stopping surprises.
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.
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.
Rule: If it’s fiddly, has torque, or needs test—make it a module.
1.3.3 BOM that the floor can pick (columns that matter)
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.
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)
- Label bin (locked to SKU), program card, torque map print.
- L1 modules: trays, fan wall, I/O, harness set.
- Small parts totes: screws by torque group (color cups), spacers, washers.
- Consumables: TIM kit, threadlock, tape, gaskets (sealed & dated).
- Accessories: cords, rails, manuals, region items.
Color bands on the cart = Variant (e.g., A=Blue, B=Orange).
1.3.5 Material readiness gates (no kit, no start)
The line starts only when the kit passes these:
- Variant check — Cart barcode = SKU/Variant; MES unlocks SWI, label map, and test only on match.
- Subassembly status — L1 modules show PASS in MES (with their own SNs/earth test where relevant).
- Critical-lot scans — PSU, PSU earth strap, harness SN, gaskets, TIMs, adhesives (lot/expiry), labels (region).
- Torque & tools — Drivers in cal; bits present; torque map printed on the cart.
- 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.
1.3.6 Shortage playbook (calm, visible, reversible)
Ladder (in order):
- Use AVL alternate (same spec) — MES swap with reason code.
- Variant swap (if safe): run SKU B while A is short—product wheel helps.
- Partial build to a clean hold point (e.g., up to lid close) — park in WIP-HOLD with red tag & list.
- Module pull from supermarket — keep the box line moving.
- 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.
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.
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.
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.
1.3.10 Common traps → smallest reliable fix
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