What is Bill of Materials (BOM)?

Bill of Materials : BOM is a complete, formally structured list of components (raw or semi finished materials), which are needed to manufacture a finished product. The BOM list contains the material number together with quantity and unit of measure of each component. The header of the BOM contains the information of the material whose BOM is to be maintained. 

Bill of Materials are used for different purposes. The usage depends on the enterprise area, for example:

The engineering/design bill of materials includes all the elements of the product (from an engineering viewpoint) and contains the technical data. It is usually not dependent on the order.

The production bill of materials includes the items (from a production viewpoint) and assembly conditions. For the assembly, for example, only items relevant to production with process-oriented data are required.

The costing bill of materials reproduces the product structure and forms the basis for automatic determination of the material usage costs for a product. Items that are not relevant for costing are not included in these bills of materials. 

Bill of Materials (BOM) Validity

Area of Validity – The same Bill of Materials can be allocated to several plants. Before you can allocate the BOM to a different plant, the material must exist at the new plant, the unit of issue on the BOM item must be the same. 

Validity Period (Valid from/to dates)

1), Becomes effective with the valid from date

2), The validity date is determined by the system automatically to be either the next effective from date, or 12/31/1999.

Bill of Materials (BOM) Scrap Data

Assembly Scrap – Yield or process scrap resulting from the assembly of components into a finished or sub-assembly. It is used for calculating material used in an assembly. MRP increases the material requirements for all components contained in the assembly.

Example: Quantity to produce 1000 units with a 1% assembly scrap = 10 units

Component Scrap – Considers component loss before the component is used in an assembly. For example, shrinkage during storage. The scrap refers only to the component in the assembly. When the BOM is exploded, MRP increases the quantity of the component.

Example: Component Qty of 1000 units with a 5% component scrap would need 1050 units required.

Operation Scrap – scrap resulting from “inter-operation” scrap during an inspection process that is not sent ahead to the next operation. When you enter operation scrap, you must also set the operation net indicator which determines that the operation scrap is calculated exclusive of the assembly scrap.

Bill of Materials (BOM) Structure

Bill of Materials Glossary

BOM Category – Categorizes BOM’s to represent different objects; for example:

Material BOM — Structure of products manufactured

Equipment BOM — Structure of equipment for plant maintenance

Document BOM — Structure of documents such as drawings (3.0)

BOM Group – Collective number for all BOM’s in a group which allows for one or several similar products to be decribed less than one number.

All Alternatives of a multiple Bill of Material

All variants of a variant Bill of Material

BOM Usage – Special view of the BOM which represents a specific area of the company in which the BOM is used; for example, Engineering, Production, Costing, Sales, Plant Maintenance. The BOM Usage allows different views to exist without separate BOM’s for each usage. 

Technical Type – the system distinguishes BOM’s according to whether they represent product variants or production alternatives. If you create a variant for the BOM, the system marks it as a Variant Bill. If there is more than one alternative for a material, the system marks the BOM as a Multiple Bill.

BOM Validity – Bills of Material are valid over an area and effectivity period.

• Area of Validity — identifies which plants the BOM has been allocated to
• Validity Period — identifies the from and to affectivity dates.  The default to date is 12/31/9999 

Item Category – When you enter a new Bill of Materials item, an item category must be assigned. It has important control functions such as:

• Screen selection
• Specific Processing, such as material number required, negative values supported.
• The Item Category cannot be changed once set.  It must be deleted and re-added.
• Sizes are maintained for variable-size items
• Item categories include:
• Stock Items — Material in stock as a component
• Non-stock Items — Material not stocked – with or without a material number
• Variable-size — System calculates the quantity required using formulas
• PM Structure Item — Used with plant maintenance equipment
• Document Item — Used with Document BOM’s 

Sub-Items – are typically used to represent different installation points for partial quantities of an item.

• In assembling resistors on a printed circuit board, the installation points are described.
• There is no logic related to sub-items

Also See: Special Stocks and Procurement Types in SAP MM an Overview