Maintenance BOMs for spare parts

A maintenance bill of material (BOM) structures a technical object from the maintenance point of view and lists its spare parts. SAP's training names three jobs for it: it shows the object's structure clearly, it lets planners pick spare parts when planning an order, and it lets them plan spare parts in a task list. It differs from a production BOM because it holds only items relevant to maintenance.

Three kinds of maintenance BOM

The material BOM is the efficient choice when several identically built objects need maintenance. Instead of one BOM per machine, you create a material, give it a BOM, and enter that material number in the construction type field in the Structure view of each piece of equipment or functional location. Contoso's three winding machines are the same model, so Rosa maintains one material BOM on construction type material CMC-WM-3000 and assigns it to all three. Change the BOM once, and every machine sees the change.

Usage and items

Every BOM has a BOM usage. In the standard system, usage 4 is plant maintenance, and SAP's documentation states that BOMs with usage 4 are relevant only to maintenance; production cannot use them. Each item has an item category: stock items are planned from stock and create reservations on an order; non-stock items are bought for the job and create purchase requisitions; text items carry notes. Contoso's tension sensor is a non-stock item because Detroit uses about two a year.

When Rosa plans an order for the winding machine, she opens the component overview and chooses the structure list. SAP explodes the BOM and shows its items; she ticks the bearing and the belt and they become components on the operation, already with the right material numbers and units. That is the real payoff of maintenance BOMs: fewer wrong part numbers on orders, and therefore fewer wrong parts at the machine.

Some parts are complex enough to be maintained in their own right but are not worth an equipment record, such as a gearbox assembly made of a dozen spare parts. SAP supports assemblies for this: a material, typically of a dedicated material type, that has its own BOM and appears as an item in a higher-level BOM. Notifications and orders can reference the assembly together with the equipment, so a technician can report "bearing on the gearbox assembly of winding machine 10000451" with precision. Contoso keeps assemblies to a minimum and introduces them only where the breakdown history shows that the extra precision pays off.

BOMs have validity dates, like other master data. When Detroit switches to a new bearing type in March, Rosa can change the BOM with a valid-from date so that orders planned before March still show the old bearing and orders planned after show the new one. That keeps the planning history honest and avoids a one-day scramble to update every open order.

Walkthrough: creating the shared material BOM

1. Create material CMC-WM-3000 as the construction type (Contoso uses a non-valuated material type for construction types; check your material types).
2. Create its BOM with CS01, plant 1710, usage 4. Add items: spindle motor, bearing and belt as stock items (category L), the tension sensor as a non-stock item (category N) with purchasing data.
3. Enter CMC-WM-3000 in the construction type field of each winding machine's Structure view (equipment 10000451, 10000452 and 10000453).
4. Create a test order on 10000452 and open the structure list: the BOM items must appear without any equipment BOM of its own.