In this guide 6 sections
A bill of materials lists every component. A routing lists the operations. A work order applies both to a stated quantity, a start date and a customer, as one live job on the floor. The BOM drives purchasing, the routing drives labour and machine cost, and the work order drives what each operator does at the machine today.
The bill of materials is the ingredient list
A bill of materials names every component of one finished unit with its quantity, so a pump housing lists a casting, four studs, a gasket and a nameplate.
Many BOMs have levels. The finished pump sits at the top, the sub assembly below it, the raw items below that, and each level carries its own part number and its own revision.
Purchasing reads this record. Multiply each line by the order quantity, subtract stock on hand and open purchase orders, and the buying list appears, with shortages shown first.
- Part number and description
- Quantity per unit and unit of measure
- Scrap allowance for cut or machined items
- Revision and effective date
The routing is the sequence of operations
A routing says how it is made. Each step names the operation, the work centre, the setup time and the run time per piece, as in sawing, turning, drilling, deburring and inspection.
Accounts reads this record for conversion cost. Hours at a work centre multiplied by its hourly rate give labour and machine cost per unit, before any overhead is added.
A planner reads it for capacity. Drilling takes six minutes a piece. With 500 due, that is fifty hours.
- Operation number and name
- Work centre or machine
- Setup time and run time per piece
- Inspection points and tools needed
The work order is the live job
A work order is one instruction to make a stated quantity of a part by a stated date for a named customer or stock location. It copies the BOM and routing at release, so later edits to the masters do not disturb a job already on the floor.
Materials are issued against it. Operations are reported against it. Finished pieces are received against it. At the close, its balance shows what the job really used of bar stock, spindle hours and inspection time compared with what the routing and BOM had allowed.
The BOM and routing are the plan. The work order is the event.
Which record drives which decision
Purchasing follows the BOM. Costing follows both the BOM and the routing, then compares those standards with the work order’s actual issues and hours once the job is closed. Floor instructions come from the routing.
Mix-ups are common here. Adding a drilling step to one work order helps that job only, while adding it to the routing helps every future job and every quote.
Ask whoever edits a record whether they are touching the BOM, the routing or the work order, and ask every single time.
Check yours with one part
Take one part your plant makes often. Print its BOM, its routing and its last work order, then lay all three on one table and read them line by line.
Look for a stud issued but missing from the BOM, a deburring step done but absent from the routing, or a turning time far from plan. Each gap is a costing error.
Bring the planner and accounts together. Fix the master records first, before the next work order is released, so the corrected stud count and deburring step reach the next job without a manual note.
BOM, routing and work order comparison sheet
Three blocks share one page for a single part number: components with quantity and scrap allowance, operations with work centre and times, and issued material with reported hours. A variance column shows planned against actual.
Open a blank worksheet to printQuestions owners ask
Is a recipe the same as a bill of materials?
In food and chemical work, a recipe or formulation plays the BOM role, listing inputs and quantities per batch for a mixer, kettle or reactor. A process sheet plays the routing. The batch record then plays the work order, because it ties the recipe to a quantity, a date and the lot that results.
Can a small shop work without routings?
Yes, for simple jobs costed on material. Once you quote on labour or machine hours, a routing becomes the record that makes the quote repeatable, so two planners price the same bracket alike. Write routings for the three busiest parts first, then add the others whenever a quote needs a labour or machine hour figure.
What happens if the BOM changes after a work order is released?
Usually nothing happens to the open job, because the work order holds its own copy of both records from the day it was released to the floor. Decide who may change an open job, such as the planner or the shift supervisor, and record each change as a note on the order itself.
Who should own these records?
Engineering or the planner should own the BOM and routing, while production supervisors own the work orders and report actual hours against them. Accounts reads all three but edits none. Anyone may ask for a change, but a named person approves it, dates it and records the reason in the revision note.