1.4 Master data model & SSOT rules: BOM, routing, resources

Master Data functions as the executable code of the factory. If the Bill of Materials (BOM) or Routing contains an error, the MES will unknowingly automate the production of a defect. Therefore, Master Data must not be treated merely as static documentation, but as a rigid configuration set that requires careful version control, validation gates, and data integrity checks.

Canonical master data entities

A production process relies on four distinct data entities. Each entity must have a unique immutable identifier (Primary Key) to prevent ambiguity.

1. Bill of Materials (BOM)

• Definition: The hierarchical list of components and raw materials.
• Primary Key: PartNumber + Revision (e.g. PCBA-1001-Rev02).
• Constraint: A BOM should not be modified in place. Any significant change generally requires a new Revision ID to maintain traceability.

2. Routing (bill of labor)

• Definition: The sequential list of operations, capable work centers, and standard times.
• Primary Key: RouteID + Revision.
• Constraint: Every Operation Step must map to a valid Resource Type.

3. Resources (work centers)

• Definition: Physical assets (Machines, Lines, Benches) or Logical groups (Test Stations).
• Primary Key: AssetID (Physical) or ResourceGroupID (Logical).
• Constraint: Resources must have an Active / Maintenance / Decommissioned state flag.

4. Recipes / programs

• Definition: Machine-specific files (Pick & Place placement files, Reflow profiles, In-Circuit Testing (ICT) test scripts).
• Primary Key: ProgramName + Checksum (MD5/SHA256).
• Constraint: The Manufacturing Execution System (MES) should verify that the machine loaded the exact program specified in the Routing before processing begins.

Pro-Tip: The Engineering Bill of Materials (EBOM) must be decoupled from the Manufacturing Bill of Materials (MBOM). Engineering designs by function; Manufacturing builds by assembly step. The MBOM is consumed by the MES.

Synchronization logic

The integrity of the system depends on the proper alignment of these entities. The following logic should be considered to enforce the “Digital Triad” (Bill of Materials (BOM) + Route + Work Instruction).

• When a Bill of Materials (BOM) Revision increments (e.g. Rev A to Rev B), the system should flag the associated Routing for review, as new parts frequently necessitate changes to the assembly process.
• When the active Work Instruction Revision does not match the Active Routing Step Revision, the system should block the operation to prevent building to obsolete prints.
• When the Recipe Checksum currently loaded on the machine does not match the approved Checksum stored in the MES Master Data, trigger an alert or interlock to halt the process until verified.

Lifecycle state machine

Data typically matures through defined states. The implementation of a State Machine helps prevent the premature or unauthorized usage of data on the shop floor.

State definitions

1. Draft: Under construction. Visible to Engineers only. Action: Block from Production Orders.
2. Pending Approval: Locked for editing. Awaiting Quality Assurance (QA)/Production Manager signatures.
3. Released (Active): The Single Source of Truth (SSOT). Available for scheduling.
4. Obsolete: Legacy data. Action: Block from new Orders. Retain only for historical genealogy.

Transition rules

Data transition rules

• When the State is set to “Released,” the record should be locked as Read-Only.
• When a modification is required on a Released record, the system should encourage the creation of a new Revision (Rev N+1).
• When a critical quality issue is detected, authorized personnel have the ability to force the State to “Hold” or “Obsolete” to prevent further use.

Drift controls & reconciliation

Over time, the ERP (Financial view) and MES (Manufacturing Execution System) will drift apart without active policing. These automated controls must be implemented to detect and block drift.

1. Blocking conditions

• Checksum Mismatch: Before releasing a Work Order, the system should calculate the hash of the combined Bill of Materials (BOM) and Routing. If the calculated hash of the Order does not match the hash of the approved Master Data, flag or quarantine the Order for review.
• Ghost Resources: If a Routing specifies a Resource (e.g. Resource_A), but that Resource is currently flagged as “Decommissioned,” the system should restrict scheduling.

2. Reconciliation reports

A nightly comparison job must be run between ERP and MES databases:

• Orphaned Parts: Items existing in MES BOMs but deleted/inactive in ERP.
• Unit of Measure (UoM) Conflicts: ERP uses “Each”, MES uses “Meters”. Action: Flag for manual correction.

Change control: ECO & flushing strategy

Engineering Change Orders (ECO) naturally introduce some risk. Defining exactly how a change enters the production stream is beneficial to avoid mixing revisions unintentionally.

Effective date logic

• Immediate: The line must be stopped. All WIP must be purged. The new revision must be setup. (Only for Safety/Critical Quality).
• Rolling (Flush): Current WIP is allowed to finish on Old Revision. New Orders are started on New Revision.

WIP compatibility logic

• When a change affects Form, Fit, or Function, it is usually necessary to purge the existing WIP or route it for documented rework.
• When a change is primarily limited to documentation, you may safely allow the existing WIP to complete its normal routing.

Versioning syntax standard

Ambiguity can hinder traceability. The adoption of a clear syntax helps distinguish prototype data from mass production data.

• Pre-Production: Use Decimal or Alphanumeric (0.1, 0.2, A, B).
• Mass Production: Use Integers (01, 02, 03).
• Rule: A change in a child component (Part A → Part B) should ideally force a revision increment of the parent assembly.

Final Checkout: Master data model + SSOT rules (BOM/routing/resources)

Category	Metric / Control	Threshold / Rule
State	Production Gate	Only “Released” state is executable.
Integrity	Immutability	Released records are Read-Only (No “Edit”, only “Revise”).
Alignment	Triad Check	BOM + Route + WI revisions must match.
Drift	Nightly Reconciliation	0 Orphaned Parts; 0 UoM conflicts.
Recipes	Machine Control	Recipe Checksum in MES = Recipe Checksum on Equipment.
ECO	WIP Handling	Defined “Flush” vs “Purge” strategy for every change.
Access	Approvals	Min. 2 Signatures (Engineering + Quality) to Release Master Data.