Routing in Manufacturing: What It Is and How It Works With the BOM
A bill of materials tells you what goes into a product.
A routing tells you how it gets made: which operations, in what order, on which work centers, and how long each one takes.
Most manufacturers put serious effort into their bills of material, because a missing component stops a job. Routings get less attention, because a wrong run time does not stop anything. It just quietly makes the schedule unrealistic, the capacity plan wrong, and the product cost inaccurate.
That is why the routing is one of the most important records in a manufacturing ERP, and one of the most neglected.
This guide explains what a routing is, what it contains, how it works with the BOM, how it drives scheduling, capacity, and costing, and how to keep routings accurate.
What Is a Routing in Manufacturing?
A routing is the sequence of operations required to manufacture an item, with the work center, setup time, run time, and other details for each operation.
When a work order is created, the routing becomes the job’s plan: the list of steps the shop floor follows, the basis for scheduling each step, and the standard against which actual labor and machine time are measured.
Routings are also called process routings, routing sheets, or operation sheets. On the floor, the printed version usually travels with the job as a traveler.
Routing vs. Bill of Materials
| Bill of materials (BOM) | Routing | |
|---|---|---|
| Answers | What goes into the product? | How is the product made? |
| Contains | Components, subassemblies, and quantities per unit | Operations, work centers, setup and run times |
| Drives | Material requirements, purchasing, and material cost | Scheduling, capacity, labor, and overhead cost |
| Owned by | Usually engineering | Usually manufacturing or industrial engineering |
| When it is wrong | Shortages, wrong material cost, failed backflushes | Unrealistic schedules, wrong capacity, wrong labor cost |
Together they define the full cost and plan of an item: materials from the BOM, conversion cost from the routing. For the BOM side, see our guide to bill of materials management.
What a Routing Contains
Each operation on a routing typically includes:
- Operation number, often in increments of 10 (10, 20, 30) so steps can be inserted later.
- Description of the work, such as “CNC mill pockets” or “Final inspection.”
- Work center where the operation runs: a machine, a group of similar machines, a cell, or a labor area.
- Setup time, incurred once per lot regardless of quantity.
- Run time, per unit or per batch.
- Labor and machine time, which may differ. One operator may run two machines, or a machine may run unattended.
- Crew size when an operation needs more than one person.
- Queue, wait, and move times between operations, which often account for most of the manufacturing lead time.
- Work instructions, drawings, and quality checks for the operation.
- Tooling or fixtures required.
- Outside operation details when the step is performed by a vendor.
A Routing Example
A routing for a machined steel bracket:
| Op | Description | Work center | Setup (hours per lot) | Run (hours per unit) |
|---|---|---|---|---|
| 10 | Cut bar stock to length | Saw | 0.25 | 0.02 |
| 20 | Mill profile and holes | CNC mill | 1.00 | 0.12 |
| 30 | Deburr | Bench | 0.00 | 0.03 |
| 40 | Powder coat | Outside vendor | — | 3 days lead time |
| 50 | Final inspection | QA | 0.00 | 0.01 |
How Setup Time and Lot Size Change Unit Cost
Setup time is spread across every unit in the lot, so the same routing produces different unit times at different quantities.
For a lot of 100, the in-house operations take:
- Saw: 0.25 + (100 × 0.02) = 2.25 hours
- CNC mill: 1.00 + (100 × 0.12) = 13.00 hours
- Deburr: 100 × 0.03 = 3.00 hours
- Inspection: 100 × 0.01 = 1.00 hour
That is 19.25 hours, or 0.1925 hours per unit.
For a lot of 25:
- Saw: 0.25 + (25 × 0.02) = 0.75 hours
- CNC mill: 1.00 + (25 × 0.12) = 4.00 hours
- Deburr: 25 × 0.03 = 0.75 hours
- Inspection: 25 × 0.01 = 0.25 hours
That is 5.75 hours, or 0.23 hours per unit, nearly 20% more time per bracket.
This is why quoting from an average unit cost goes wrong on small orders, and why reducing setup time is so valuable: it lowers the cost of every small lot and makes smaller, more frequent runs practical.
What the Routing Drives: Scheduling, Capacity, and Cost
Scheduling
The routing defines each operation’s duration and sequence. Scheduling uses it to decide when each step runs on each work center. See our guide to production scheduling.
Capacity Planning
Multiply routing times by planned quantities, sum by work center, and you have the load. If the routing understates the CNC run time by 20%, the capacity plan understates the load on the CNC by 20%. See our guide to capacity planning.
Product Cost
Routing times multiplied by labor rates and overhead rates produce the conversion cost of the item. In a standard cost system, that becomes the standard. When actual time differs, the result is a labor efficiency variance. See manufacturing cost variances.
Lead Time
Setup, run, queue, and move times together determine how long a job takes, which drives promise dates and MRP’s planned lead times.
Shop Floor Execution
The routing is what operators see on the traveler or terminal: what to do next, with which instructions and drawings, and what to report when they finish.
Linking Materials to Operations
In a simple setup, all components on the BOM are issued at the start of the job. In many plants, materials are actually consumed at specific operations: fasteners at assembly, paint at finishing, packaging at the last step.
Linking each BOM component to the operation where it is used gives you:
- More accurate WIP, because material moves into the job when it is actually consumed. See our guide to WIP inventory.
- Later material requirements dates, so components can arrive just before the operation that needs them, instead of at job start.
- Picking and staging at the right place on the floor.
Alternate Routings and Outside Operations
Alternate Routings
An alternate routing defines a different way to make the same item, such as a second machine, a different cell, or outsourcing a step when the primary work center is overloaded. Alternates give the scheduler options without changing the item.
Outside Operations
When a step such as plating, heat treating, or coating is done by a vendor, it should still appear on the routing as an operation. That lets the system:
- Create a purchase order for the service, tied to the job.
- Track that the parts are at the vendor, so they do not disappear from WIP.
- Include the vendor’s lead time in the job’s schedule.
- Add the service cost to the job when the parts come back.
Routings in Process Manufacturing
Process manufacturers often use the term less, but the idea is the same. A formula or recipe defines the ingredients, and a process definition defines the steps: weigh, mix, cook, cool, fill, package. Steps may have fixed durations, such as a 4-hour cure, regardless of batch size.
In mixed-mode plants, a process operation often feeds a discrete one, for example a batch that is mixed and then packaged on a filling line. Both need to be planned and costed in the same system. See our guide to discrete vs. process manufacturing ERP.
How to Keep Routings Accurate
- Compare actual to standard regularly. If labor and machine time are reported by operation, the system can show where actual times consistently differ from the routing.
- Separate setup from run time when reporting, so you can tell whether a variance is a setup problem or a cycle-time problem.
- Use time studies for new or high-volume items, and historical actuals for the rest.
- Update routings through a controlled change process, the same way BOM changes are handled, so open jobs, costs, and capacity plans update together.
- Review queue and move times. They are often set once and forgotten, and they drive lead time.
- Assign ownership. Every routing should have someone responsible for keeping it current.
Common Routing Mistakes
- Copying a similar part’s routing and never correcting it.
- Combining several operations into one, which hides where time and cost are actually spent.
- Leaving out inspection, packaging, or outside operations, so they are missing from both the schedule and the cost.
- Using best-case run times, which makes every job look inefficient and every schedule late.
- Ignoring the difference between labor and machine time when one operator runs several machines.
- No queue or move time, which makes lead times look shorter than they ever are.
Routings in Manufacturing ERP
In a manufacturing ERP, the routing is not a document. It is live data that feeds scheduling, capacity planning, MRP lead times, costing, and the shop floor at once. When the routing changes, everything that depends on it updates.
How Bizowie handles it: Bizowie Cloud ERP supports full multi-level subassemblies with automatic creation of dependent work orders, and keeps track of labor and machine capacity schedules by work center. Labor and machine time are recorded from the shop floor and applied as direct costs, and third-party processes are managed within the work order. Custom travelers and labels can be printed with work order details and barcodes, and the BOM, work instructions, and drawings can be pushed directly to the employee’s workstation. Controlled drawings, ECO/ECRs, and quality data can be managed in the same platform through its document management capabilities.
For more, see our manufacturing ERP software buyer’s guide and our guide to work order management.
Frequently Asked Questions
What is the difference between a routing and a BOM?
A bill of materials lists the components and quantities that go into a product. A routing lists the operations, work centers, and times required to make it. The BOM drives material requirements and material cost; the routing drives scheduling, capacity, and labor and overhead cost.
What is setup time vs. run time?
Setup time is the time to prepare a work center for a job, such as changing tooling or loading a program, and it is incurred once per lot. Run time is the time to process each unit or batch, and it scales with quantity.
What is a traveler in manufacturing?
A traveler is the document, printed or electronic, that accompanies a job through the shop. It typically shows the work order, the routing’s operations, materials, instructions, and spaces or barcodes for reporting progress.
What is an alternate routing?
An alternate routing is a different approved way to make the same item, such as using a different machine or outsourcing an operation. It gives schedulers flexibility when the primary work center is overloaded or down.
How often should routings be reviewed?
Review routings whenever a process changes, and compare actual to standard times at least quarterly for high-volume items. Any operation that consistently runs well over or under its routing time should be updated.
Do process manufacturers use routings?
Yes, though they may call them process steps or process definitions. A formula or recipe defines the ingredients, and the process steps define the equipment, sequence, and durations, which drive scheduling and conversion cost in the same way.
Bring Us a Routing That Never Matches Reality
If your routings say one thing and your floor does another, bring us an example:
- A part whose run times were copied from something else.
- A job with an outside operation that keeps going missing.
- A product whose cost changes with every lot size.
- A process step that feeds a packaging line.
We’ll show you how Bizowie would model it, schedule it, and cost it, and if the platform is not a good fit for your operation, we’ll tell you that too.