ERP for Manufacturers: Bills of Material, Routings and Actual Costing
Short answer: what separates a manufacturing ERP is not the module list but how the bill of material, routing and work centre chain feeds costing. An ERP claiming to "have a production module" is not necessarily able to calculate actual cost. This article lists the technical questions manufacturers should ask during evaluation.
Why a standard ERP falls short in manufacturing
For a trading company an ERP is purchase, sale, stock and accounting. In manufacturing four new concepts enter that chain:
1. Bill of material: which components make up a product, across multiple levels.
2. Routing: which operation runs on which work centre, with what setup and run time.
3. Work centre cost: allocating energy, depreciation, labour and overhead to machine hours.
4. Actual consumption: materials and time actually used, not theoretical figures.
Without these four an ERP sees production only as stock movement: raw material out, finished goods in. The difference between them is never measured.
Standard cost or actual cost?
They answer different questions and both are needed.
Standard cost is for planning: quoting and budgeting. It is set at the start of a period and stays fixed.
Actual cost measures what happened: how much material and time each work order consumed. The variance between standard and actual is the number management should watch.
The evaluation question is: "At what level of detail can you show the variance between standard and actual?" If the answer is "per product" it is insufficient; the variance must split into material and time and be visible by line and shift.
Bills of material: five things to check
- Versioning. When a recipe or BOM changes, are past productions still calculated with the old version? Without versioning, the cost of closed periods changes silently.
- Alternative components. Can two materials serving the same purpose be defined? During supply shortages this is the only structure that keeps production running.
- Scrap rates. Can scrap be defined per component? A single global scrap rate does not reflect reality.
- By-products and scrap returns. Can secondary output enter stock and reduce cost?
- Phantom levels. Can non-stocked intermediates appear in the structure without generating stock records?
Routings: four things to check
- Are setup and run time separate? On small batches most of the cost is setup; without separation the calculation drifts as quantity grows.
- Are alternative routings supported? If the same product can run on different machines, its cost differs; a single routing hides that.
- Is subcontracting a routing step? Outsourced work must reconcile quantities sent and returned with the subcontractor invoice.
- Is capacity planning finite or infinite? Infinite capacity always says "it fits" and never reveals the bottleneck.
Data capture: the most skipped step
Actual cost cannot be calculated without data from the floor. Three methods exist:
1. Manual entry (terminal or paper): fastest to start, accuracy depends on discipline.
2. Barcode/terminal: operation start/stop capture; a balanced solution.
3. Automatic machine capture (counters, PLC, OPC-UA): most accurate, most expensive, longest to build.
The sequence that works in practice: a manual period first, automatic capture second. The manual period produces the reference against which automatic data is validated. Going straight to automation leaves counter faults undetected for a long time.
Critical requirements differ by sector
- [Food manufacturing](/en/industries/food-beverage-manufacturing): batch traceability, shelf life, FEFO, recipe versions.
- [Plastics](/en/industries/plastics-manufacturing): mould management, cycle times, machine-level costing, regrind ratio.
- [Metal and machinery](/en/industries/metal-machinery-manufacturing): quote costing, subcontracted operations, project cost accumulation.
- [Packaging](/en/industries/packaging-manufacturing): multi-unit conversion, reel and remnant tracking, tolerance delivery.
- [Textiles](/en/industries/textile-apparel): style-variant hierarchy, size runs, subcontractor tracking.
The same "production module" must do different things across these five. Do not decide without seeing your own sector's items in the demo. How to turn product choice into a matrix is covered in the [ERP selection guide](/en/blog/erp-selection-guide), and the cost lines in [the real cost of an ERP project](/en/blog/erp-consulting-guide).
Technical questions for evaluation
- How is cost accumulated in a multi-level BOM, and at which level is it cut off?
- Are BOMs and routings versioned? Does recalculating a past period change the result?
- Where does actual consumption come from — terminals, scales, counters?
- Which elements make up the work centre hourly rate, and how are they allocated?
- Is rework a distinct operation type or does it blend into normal production?
- Is capacity planning finite? Can the bottleneck work centre be reported?
Is a manufacturing ERP enough on its own?
In most manufacturers the ERP is the core but not the only system. It is usually joined by [mobile applications](/en/solutions/mobile-app-development) for shop-floor and warehouse terminals, a [B2B portal](/en/products/b2b-dealer-portal) for dealer orders, [bank integration](/en/products/bank-integration) for collections and reconciliation, and [time and attendance](/en/products/time-attendance) for shifts. Unless how these talk to the ERP is defined at the start, each becomes its own data island.
Frequently asked questions
Our ERP has a production module but we do not use it. Why?
The most common reason is that BOM and routing data were never built. The module is available but produces nothing because nothing feeds it. In that case the ERP does not need replacing; the data model does. That is typically far shorter than a new ERP project.
What is needed to run MRP?
At least three things: accurate bills of material, reliable stock and realistic lead times. If any one is missing, MRP output is unusable and the team quickly stops trusting it.
Does collecting production data require stopping the plant?
No. Data capture is built alongside the existing flow and started on a pilot line. The only step usually needing downtime is fitting a physical counter or connection to a machine, and that is done in a planned maintenance window.
What is the difference between ERP and MES?
The ERP plans and calculates cost; MES manages real-time execution on the floor. In small and mid-sized plants the ERP production module covers most needs. MES becomes relevant when second-level resolution and line automation are required.