Routing and Operation Sequencing – Defining How Work Actually Flows Through the Plant

This topic is part of the SG Systems Global regulatory & operations glossary.

Updated November 2025 • BOM, Work Order Execution, Equipment and Line Assignment, EWI Management, ISA‑88, MES, ERP, Finite Capacity Scheduling, Change Control, Data Integrity
• Planning, Ops, Tech Ops, QA, Engineering, CI, Digital

Routing and operation sequencing is how you define, in systems and procedures, the path a product or batch takes through equipment, operations and lines – and the order in which those operations must occur. Where the BOM tells you what goes into a product, routing tells you how and where work is performed, and operation sequencing tells you in what order work happens, including setups, inspections, holds, cleaning and packaging.

In a simple plant, routing lives in people’s heads: “we always run that SKU on line 2, then put it through the spiral cooler.” In a regulated or high‑complexity environment, that tribal knowledge does not cut it. The validated process, the schedule, the MES recipe and the EWIs all have to agree on the route and the sequence – and changes must be controlled, not improvised on the day.

“If your official routing says one thing, your whiteboard says another and the operators do a third, you do not have a clever flexible plant – you have three conflicting versions of reality and no single source of truth.”

1) What We Mean by Routing and Operation Sequencing

There are a few terms that often get mixed together:

• Routing:
  • The defined path a product or batch follows through operations and work centres – for example: receive flour → condition → mix → bulk ferment → divide/round → proof → bake → cool → slice → pack → palletise.
• Operations:
  • Individual steps or activities that consume time and capacity: weighing, mixing, loading oven, baking, cooling, QC checks, cleaning, format changeover.
• Operation sequencing:
  • The ordering and dependency logic for operations, including parallel steps, overlaps, wait times, holds and branching (for example, rework flows).
• Work centres / resources:
  • Logical or physical groupings of equipment and labour that perform operations – mixers, proofers, ovens, fillers, packers, inspection cells.

Routing defines the structure of the process. Operation sequencing defines the logic of execution in time. Together, they answer three questions for every work order: where does it go, what happens there and in what order are those things allowed to happen.

2) Why Routing & Operation Sequencing Matter

It is easy to treat routing as an ERP master‑data chore. That is how you end up with routing tables that nobody trusts and production plans that fall apart by 9 a.m. In reality, routing and sequencing drive:

• Capacity and service:
  • Realistic routings and operation times are the backbone of capacity models and schedules. If they are wrong, every promise date is a guess.
• Cost and OEE:
  • Routings decide where setups, cleaning and quality holds sit. Good sequences minimise idle time and changeovers; bad ones bake waste into the plan.
• Quality and compliance:
  • In GxP and audited food, the validated process, EWIs and batch record must reflect the real route and sequence. Deviating from that without control is non‑compliance.
• Safety and ergonomics:
  • Routing decisions affect material flows, cross‑traffic and manual handling. They can reduce or create safety risks depending on how thoughtfully they are designed.
• Digital effectiveness:
  • MES, data lakes and analytics are only as good as the model of the process they sit on. Broken routing means misleading KPIs and machine‑learning models optimising the wrong thing.

If you have constant firefighting, unstable schedules, nasty surprises in capacity and a habit of explaining everything as ‘special cause’, chances are your routing and sequencing are nowhere near as solid as you think they are.

3) Core Concepts – Routings, Operations and Work Centres

Before jumping into systems, get the vocabulary straight.

• Master routing vs order routing:
  • Master routing is the template path for a product or family.
  • Order routing is the instantiated path for a specific work order on a specific date, possibly with equipment or path choices resolved.
• Operations and phases:
  • Operations can be high‑level (mixing, baking) or broken into phases (charge, heat, hold, cool) as per ISA‑88. The right level of detail balances usefulness with maintainability.
• Primary vs secondary operations:
  • Primary operations transform the product. Secondary operations support the process (cleaning, changeovers, inspections, staging). Secondary steps still consume capacity and must be in the sequence if you want realistic schedules.
• Work centres and resources:
  • A work centre might be a single asset (line 3 oven), a cell (pack line A) or a logical group (mixing area). Resources include machines, people and sometimes tooling (pans, moulds, change parts).
• Alternative routings and operations:
  • Some products can run via different paths: different lines, different packaging formats, different technologies. Alt routings encode those options instead of leaving it to tribal memory.

If all you have in ERP is a single ‘MAKE’ operation with a generic work centre called ‘BAKERY’ or ‘PRODUCTION’, you are not doing routing; you are using a modelling shortcut that hides everything important about how work actually flows.

4) Where Routing and Sequencing Data Come From

Routings should be an explicit, traceable reflection of process knowledge, not a best guess by whoever had the most time in front of the keyboard.

• Process development and tech transfer:
  • Process flow diagrams, P&IDs, scale‑up reports and tech‑transfer packages define the intended manufacturing route and critical steps.
• SOPs and EWIs:
  • Work instructions describe stepwise tasks for operators. Routings should be consistent with these, not silently diverge.
• Validation and qualification:
  • For GxP, the validated process (PPQ, cleaning validation, equipment qualification) defines which routes and sequences are allowed. Alternative paths must be validated before they appear in routings.
• Time studies and OEE data:
  • Operation times, overlaps and queue times should be informed by measured data, not wishful thinking or vendor brochures.
• Constraint and risk analysis:
  • Outputs from QRM, HAZOP, FMEA and allergen risk assessments often drive additional steps, checks or holds in the sequence.

If process development, validation and planning do not talk, routings drift away from the real process. Eventually some auditor spots that your ‘official’ route bears only a passing resemblance to what actually happens on the floor. That conversation does not end quickly or pleasantly.

5) From Master Routing to Site‑ and Line‑Specific Paths

Many companies have more than one plant or line that can make the same product family. That raises design questions:

• Global vs local routings:
  • Global or corporate master routings define standard operations, but each site may have local variations: different mixers, ovens, proofing technology, QC labs.
  • Decide which elements are global (sequence, critical steps) and which are local (operation times, work centre IDs, cleaning patterns).
• Equipment‑dependent routing:
  • A dough line running through a spiral proofer and tunnel oven has a different sequence and constraints than one using static racks and a deck oven. That difference must be explicit in routings.
• Different market / regulatory requirements:
  • Products for different markets may require different operations (extra inspection, tamper‑evident packaging, label verification). Separate routings or optional operations cover this.
• Alternative site routing:
  • Network‑level routing decides which plants are primary, secondary or contingency sources for each product. Those decisions define which site‑specific routing variants must be maintained and validated.

Trying to model radically different plant layouts and technologies with one generic ‘global routing’ usually ends with heroic local workarounds and planners ignoring the master data. Better to admit the complexity and model it explicitly than pretend everything is equivalent when it clearly is not.

6) Integration with Work Order Execution and Equipment Assignment

Routing is the structural backbone that other execution decisions hang off.

• From routing to work order operations:
  • When a work order is released, ERP or MES explodes the routing into specific dated operations with planned start/finish times and quantities.
• Link to equipment and line assignment:
  • Routings specify which kind of work centre is required; Equipment and Line Assignment chooses which physical line or asset will run each operation.
• Link to EWIs and MES recipes:
  • Each operation in the routing references the correct EWI or MES recipe segment, so that when the order is dispatched, the right instructions and parameter sets appear on the right terminals.
• Feedback loop:
  • Actual operation times, waits, downtimes and yields feed back to improve routing times and sequencing rules. If you never update routings, they quickly become fiction.

In a healthy setup, planners can trust that if an operation appears in the routing, it will show up correctly in the work order, on the line and in the batch record. If that chain is broken, people bypass systems and revert to whiteboards and memory – and all the digital investment is quietly sidelined.

7) Changeovers, Setups and Cleaning in the Sequence

The big difference between toy routings and useful ones is whether they treat setups and cleaning as first‑class citizens.

• Sequence‑dependent setups:
  • The time and tasks for setup depend on the previous and next product: format changes, allergen changes, colour changes, tooling swaps.
  • Routing and operation sequencing must be aligned with changeover optimisation logic and allergen matrices.
• Cleaning operations:
  • Line cleaning, CIP, SIP, dry clean and inspection should be explicit operations with times, resources and, in GxP, links to cleaning validation SOPs.
• Campaigning and families:
  • Operation sequencing should reflect campaign strategies – for example, light to dark, non‑allergen to allergen – not just treat each order in isolation.
• Hold times and environmental controls:
  • Proofing, fermentation, drying and cooling steps with minimum/maximum times and temperature/humidity constraints need to be modelled as operations or operation attributes.

Plants that ignore this and put only value‑adding steps in routings usually find their schedules are wildly optimistic on changeovers and cleaning, and then blame ‘unreliable operators’ instead of fixing the underlying model.

8) Digital Tools – From ERP Routings to Advanced Scheduling

Routing and sequencing logic lives in different layers of the digital stack:

• ERP routings:
  • Define high‑level operations, default work centres and basic times. Good for costing and rough‑cut capacity, weak for real‑world sequencing.
• Finite‑capacity schedulers (APS/FCS):
  • Use routings as input and apply capacity limits, sequence‑dependent setups, availability calendars and priorities to create feasible schedules.
  • See Finite Capacity Scheduling.
• MES / recipe engines:
  • Implement ISA‑88 style phases and unit procedures, control step‑level execution and capture real operation data.
• eBR / workflow engines:
  • Enforce sequencing, signatures and checks in GxP contexts, making sure no critical step is skipped or performed out of order.

Some organisations push all sequencing logic into one layer (for example, only in MES or only in APS). That is rarely sustainable. High‑level routing belongs in ERP; time‑ and resource‑constrained sequencing belongs in APS/MES; detailed step logic and checks belong in MES/eBR/EWIs. Trying to cram everything into one system usually ends with either excessive complexity or people ignoring the tool altogether.

9) Constraints, Rules and Governance in Sequencing

Routing and sequencing must respect a messy mix of constraints. Some are absolute, some are trade‑offs.

• Hard constraints:
  • Regulatory: validated paths, cleaning frequencies, required inspections, hold times.
  • Technical: limits of equipment (temperature, pressure, capacity, speed, dough absorption, rheology).
  • Safety: dust explosion zones, incompatible chemicals, allergen segregation.
• Soft constraints / optimisation targets:
  • Minimising changeovers and cleaning.
  • Balancing labour across lines and shifts.
  • Prioritising high‑margin or service‑critical orders.
  • Energy usage and utility peaks.
• Business rules:
  • Campaign size minimums, make‑to‑order vs make‑to‑stock rules, shelf‑life requirements, customer‑specific sequencing constraints.

If schedulers can override hard constraints with a drag‑and‑drop Gantt change and no system challenge, routing is not being governed properly. Conversely, if every soft preference is encoded as a ‘must’, you get rigid plans nobody can actually execute. Governance is about being explicit which is which and designing rules accordingly.

10) Roles & Responsibilities

Creating and maintaining routing and sequencing logic is a team sport. Typical ownership split:

• Technical services / manufacturing science:
  • Own the process model: steps, dependencies, scale‑up constraints, ISA‑88 recipes, critical operations.
• Planning / supply chain:
  • Own routings in ERP and scheduling rules in APS/FCS; ensure operation times and capacities are realistic and kept up to date.
• Operations:
  • Provide reality checks, identify workarounds and undocumented steps, and help refine times and sequences based on day‑to‑day running.
• QA / validation:
  • Ensure routings and sequences match validated processes and cleaning strategies; review and approve changes under change control.
• Engineering & maintenance:
  • Provide constraints and opportunities based on asset capability, planned maintenance and reliability data.
• Digital / IT:
  • Implement routing and sequencing logic across systems and ensure data models are consistent.

When nobody clearly owns routing master data, it quietly decays. Planners patch around it with spreadsheets, MES recipes fork away from ERP, and eventually nobody is willing to touch the routing tables for fear of breaking something. At that point, you are flying the plant on muscle memory alone.

11) Common Failure Modes & Audit Findings

Routing and sequencing issues are depressingly predictable:

• One giant ‘make’ step:
  • ERP has a single operation that lumps an entire process into one time bucket. Capacity planning and costing are little better than guesses.
• Routings that do not match reality:
  • Official routings omit steps operators always perform (for example, intermediate inspections, rework loops, temporary storage); batch records show a different story than ERP.
• Copy‑paste inflation:
  • New products are created by cloning routings from vaguely similar SKUs; over time, the routing library becomes a tangle of inconsistencies nobody wants to clean up.
• Unmodelled constraints:
  • Proofing, drying or hold‑time constraints are ignored in routings, so schedules look brilliant on paper and impossible on the floor.
• Shadow routing in spreadsheets:
  • Planners quietly run their own line‑by‑line operation maps and times in Excel because they do not trust ERP or MES data.
• GxP misalignment:
  • Validated process descriptions, eBR flows and ERP routings disagree on steps or sequences. Auditors notice and start asking awkward questions about how changes are controlled.

The pattern is simple: when routing and sequencing are not kept truthful and central, they reappear as uncontrolled local workarounds. Those workarounds might keep product moving, but they destroy transparency and make serious digital or CI work almost impossible.

12) EWIs, eBR and Embedded Sequencing

At the operator level, routing and operation sequencing show up as instructions and enforced workflows, not as ERP tables.

• Electronic Work Instructions (EWIs):
  • EWIs present the ordered steps, checks and set‑ups for each operation. They must align with routing; if they do not, operators are forced to choose between ‘what the system says’ and ‘what actually works’.
  • See EWI Management.
• Electronic Batch Records (eBR):
  • In GxP, eBR workflows enforce sequence, signatures, material additions, parameter checks and holds. The eBR is effectively the routing and sequencing logic, but on a per‑batch level.
• Interlocks and conditional logic:
  • Systems can prevent an operation from starting until prerequisites are complete – for example, cleaning verified, materials consumed, previous step signed off, lab release received.
• Deviation handling:
  • Where breaks in sequence are unavoidable, integrated deviation workflows allow documented, reviewed exceptions instead of undocumented shortcuts.

The ideal state is simple: for operators, routing and sequencing are invisible. They just follow screens that always present the right next step and prevent the wrong ones. You only notice sequencing because it is working – or because it is missing and chaos fills the gap.

13) Designing a Site‑Level Routing & Sequencing Framework

You do not fix routing by editing a few ERP fields. You need a deliberate design and governance approach:

• 1. Map the real process:
  • Walk the line. Document the actual steps, waits, loops, rework paths, clean‑downs, lab holds and material movements. Ignore what the systems say for now.
• 2. Define modelling levels:
  • Decide which steps belong in ERP routings, which in APS, which in MES/eBR and which only in EWIs. Avoid modelling the same thing in four different places.
• 3. Standardise structures and naming:
  • Operation naming conventions, work centre hierarchies and routing patterns should be consistent across products. That makes maintenance and analytics orders of magnitude easier.
• 4. Link to change control:
  • Changes to routing and sequencing must go through formal change control where there is any quality, safety or regulatory impact. Master‑data edits are not admin tasks; they are process changes.
• 5. Clean up iteratively:
  • Start with high‑volume or high‑risk products and lines. Fix their routings properly, prove the value, then roll out patterns to the rest of the portfolio instead of trying to big‑bang the entire plant.
• 6. Monitor and refine:
  • Use variance between planned and actual times, WIP queues and OEE patterns to spot where routing is drifting away from reality again and needs a tune‑up.

The goal is not a perfect textbook model; it is a living, controlled representation of how work really flows, accurate enough to drive decisions and simple enough that people are willing to maintain it.

14) How Routing & Operation Sequencing Fit Across the Value Chain

R&D and tech transfer: Early on, routing is just process flow diagrams and lab procedures. As products move to commercial scale, that conceptual flow becomes routings, unit procedures and MES recipes. Getting that right avoids ‘re‑discovering’ the process at every new plant.

Sales & S&OP: Promise dates and feasible scenarios depend on honest capacity models, which depend on realistic routings and operation times. If the routing library is junk, S&OP is theatre and capacity investments are guesswork.

Manufacturing & CI: Line balancing, debottlenecking, SMED, campaign design and replenishment pathing all rely on a clear understanding of the process sequence. Without it, improvement work degenerates into local firefighting.

Quality & regulatory: In GxP and retailer‑audited food, the defined manufacturing route and sequence underpins batch release, PQRs, complaints handling and inspections. If you cannot show a controlled link from validated process to routings to eBR/EWIs, expect findings.

Finance & costing: Operation times and routings drive labour and overhead absorption, line‑level costing and investment cases. If routing is unrealistic, product costs are distorted and portfolio decisions are skewed.

Digital & analytics: A GxP data lake, OEE dashboards and advanced optimisation depend on a stable model of how work flows. Routing and operation sequencing are that model. Ignore them, and you are essentially doing statistics on noise.

In short: routing and operation sequencing are not an ERP configuration footnote. They are the explicit, governed description of how your plant actually works. Treat them casually, and you will get the chaos you have chosen.

15) FAQ

Q1. What is the difference between routing and scheduling?
Routing defines the structural path and sequence of operations and work centres for a product or batch; it changes rarely and is part of master data. Scheduling decides when to run specific orders on specific resources, given demand, capacity and constraints. Routing is the map; scheduling is the decision about when and where to drive on that map this week.

Q2. How detailed should routings be?
Enough to be useful, not enough to become unmaintainable. High‑level routing in ERP should include all primary operations and the most impactful secondary ones (setups, cleaning, holds) with realistic times. Finer detail – instructions, parameter steps, in‑process checks – belongs in EWIs, MES recipes and eBR, not necessarily in ERP. If nobody can keep up with routing maintenance, you have modelled it at the wrong level.

Q3. When do we need alternative routings?
Alternative routings are useful when a product can legitimately run through different paths with different constraints or economics – for example, different sites, different lines, different packaging technologies or different regulatory requirements. If operators are frequently deviating from the ‘standard’ route in ways that are acceptable but undocumented, that is a sign you need to formalise alternative routings and bring them under control instead of treating them as unofficial hacks.

Q4. How does routing relate to cleaning, allergens and validation?
Routing and sequencing must Incorporate cleaning operations, allergen risk controls and steps defined in process and cleaning validation. In many regulated or retailer‑audited environments, only certain routes are validated or permitted for specific allergen or potency classes. Sending a product down an unvalidated route, even if technically possible, is a compliance failure. Modelling these rules explicitly in routing and scheduling tools is far safer than relying on people to “remember not to do that”.

Q5. Where is a practical place to start if our routings are a mess?
Pick one value stream – a line or product family that causes the most pain – and map the real end‑to‑end process with operators, planners and engineers in the room. Compare that to current ERP routings, MES recipes and EWIs, then redesign the routing for that value stream properly, including times and key secondary operations. Wire it into your scheduling and execution tools, measure the impact, and use that pattern as the template for cleaning up the rest. Trying to fix every routing at once usually results in a lot of meetings and very little change on the shop floor.

Related Reading
• Process & Execution: BOM | Work Order Execution | Equipment and Line Assignment | EWI Management | ISA‑88
• Planning, Capacity & Yield: Finite Capacity Scheduling | Yield Variance | Batch Variance Investigation | Mass Balance | GxP Data Lake & Analytics Platform
• Compliance & Governance: Data Integrity | Change Control | Deviation / NCR | CAPA | Process Validation