Routing

A routing is the ordered list of operations needed to manufacture a product. Each operation specifies the work centre or equipment, the setup time, the run time per unit, the labour grade required, the in-process quality checks, any environmental conditions (temperature, humidity, classified-area grade), and the document(s) the operator must read and sign. The routing is paired with the Bill of Materials (BOM) — the BOM tells you what materials enter, the routing tells you in what order they are transformed, by whom, on what equipment, and with what controls.

In a non-regulated factory the routing is essentially a cost-and-scheduling tool. In a regulated factory it is also a compliance object: it is the source-of-truth for the master record (MMR, MBR or DMR), it is what the kiosk enforces step-by-step at execution, and it is what the executed batch record is compared against during release review. A change to the routing is therefore a change-control event, not a spreadsheet edit.

A defensible routing step contains, at minimum, the following fields. Anything less and the executed batch record is incomplete; anything more and the operator is overwhelmed.

The same artefact has different names depending on the regulation, but the function is identical.

The BOM is the list of materials and the routing is the list of operations. Either alone is useless; together they form the complete master record of how the product is made.

• BOM line: 'API X — 250 mg per tablet — qualified supplier list AP-001 — release-tested per spec SP-API-X'.
• Routing step that consumes it: 'Step 020 Dispense API X to scale tolerance ±0.5 % — work centre Dispense Booth 2 (ISO 8) — performed by Operator with witness — record actual weight, balance ID, calibration date'.

When the BOM changes (new supplier, new spec, new strength) the routing is almost always affected (new dispense tolerance, new IPQC). A change-control process that updates one without re-evaluating the other is the root cause of a large fraction of cGMP deviations.

Paper batch records still exist, but the modern equivalent — sometimes called an electronic batch record (eBR), an electronic device history record (eDHR), or a guided-execution kiosk — turns the routing into a state machine. The operator cannot start step N+1 until step N is signed; the system blocks signature on step N until all required IPQC are within spec; the system records timestamp, user, equipment ID and any deviation reason.

This is also where the routing earns its keep at audit time. An EU GMP Annex 11 inspector walks the executed batch record line by line and expects every routing step to have a matching, signed entry; an FDA Form 483 observation is almost guaranteed if a step in the master routing is missing from the batch record, or if a step in the batch record has no parent in the master routing.

IPQC is not a separate document — it is a property of the routing step. Each test specifies what is measured, the acceptance limit, the action limit, the test method, the equipment used, the sample size, and the disposition on out-of-spec. Examples by dosage form:

• Tablets: weight variation (USP <905>), hardness, friability (USP <1216>), thickness, disintegration (USP <701>).
• Capsules: fill weight, lock length, weight uniformity.
• Liquids and suspensions: pH, viscosity, fill volume, particulate inspection.
• Sterile injectables: container-closure integrity, visible particulate inspection (USP <790>), fill weight uniformity.
• Powders and blends: blend uniformity (10 locations, typically), moisture content.
• Devices: dimensional inspection, electrical safety test, leak test, sterile-barrier integrity.

An out-of-spec IPQC is not a release decision — it is a deviation that triggers an investigation. The routing should specify the hold disposition (quarantine the in-process material, stop the line, escalate to QA) rather than leaving it to operator judgement.

The same routing that drives compliance also drives the financials. Setup time × number of changeovers + run time × volume + labour grade × headcount + equipment depreciation per hour gives standard cost per unit. Routing changes (faster equipment, removed step, parallelisation) flow directly into standard cost; standard cost variances flow back into routing review.

ISA-95 formalises this two-way flow between the business system (ERP) and the manufacturing operations system (MES): the routing is one of the canonical exchanged objects. In practice, the routing maintained in V5 (or any compliant MES) is the master; the ERP carries a simplified view for scheduling and cost. Drift between the two is a frequent source of deviations and inventory variances.

A routing change is a master-record change. The minimum control set:

1. A change request describing the change, the rationale, and the impact assessment (product quality, regulatory submission, validation, training).
2. Approvals from QA, manufacturing, engineering and (where applicable) regulatory affairs.
3. Update to the master routing with a new version number.
4. Update to dependent documents — SOPs, training matrices, label artwork if affected, validation reports if process parameters changed.
5. Effective-date control — the new routing applies from a defined batch; in-flight batches finish on the previous version.
6. Training of operators on the new routing before the effective date.

For pharma manufacturers, a routing change that affects a CMC (Chemistry, Manufacturing and Controls) commitment in an approved filing may also require a regulatory variation or supplement (FDA CBE-30, PAS, or EMA Type IA/IB/II).

1. Routing exists in the ERP but not in the quality system — manufacturing follows one version, QA reviews against another.
2. IPQC limits hard-coded in the routing but not in the LIMS — operator passes a test the lab system would have failed.
3. Equipment listed as a generic class ('blender') rather than a qualified asset ID ('Blender BL-12, last qualified 2025-11-04') — the inspector cannot tell which blender was used.
4. Routing edits made directly in production without change control — the executed batch record cites a master version that does not match the change-control log.
5. Setup and run times never revisited after the initial launch — variance reports compare actuals against an idealised standard that no batch has hit in five years.
6. Out-of-sequence step execution allowed by the system — operators 'work ahead' on a slow step and sign it later.
7. Routing copied between SKUs by clone-and-edit without re-validating the differences (different fill volume, different cleaning regime, different IPQC).

• routings table keyed by (product_id, version), with status (draft|approved|effective|retired) and effective_from / effective_to dates.
• routing_steps child table with sequence, work_centre_id, setup_minutes, run_minutes_per_unit, labour_grade_id, environmental_class_id and signature_policy.
• routing_step_ipqc child table joins each step to one or more tests with spec, method, sample size and disposition.
• Change control: any edit to an effective routing is blocked; the system forces a new draft version and a change-control record before promotion.
• Kiosk execution: each operator action writes a routing_step_execution row with timestamp, user, equipment_id, e-signature and any deviation reference.
• Release-review pack diffs the executed batch record against the active routing version and flags any missing steps, sequence anomalies or out-of-spec IPQC.