A bill of materials is a list of the raw materials, sub-assemblies, intermediate assemblies, sub-components,
parts and the quantities of each needed to manufacture an end product.
A BOM may be used for communication between manufacturing partners, or confined to a single
manufacturing plant.
A BOM can define products as they are designed, as they are ordered, as they are built, or
as they are maintained.
The different types of BOMs depend on the business need and use for which they are intended.
In process industries, the BOM is also known as the formula, recipe, or ingredients list.
In electronics, the BOM represents the list of components used on the printed wiring board
or printed circuit board.
Once the design of the circuit is completed, the BOM list is passed on to the PCB layout
engineer as well as component engineer who will procure the components required for the
design.
Modular BOMs In many cases, BOMs are hierarchical in nature
with the top level representing the finished product which may be a sub-assembly or a completed
item.
BOMs that describe the sub-assemblies are referred to as modular BOMs.
An example of this is the NAAMS BOM that is used in the automotive industry to list all
the components in an assembly line.
The structure of the NAAMS BOM is System, Line, Tool, Unit and Detail.
The first hierarchical databases were developed for automating bills of materials for manufacturing
organizations in the early 1960s.
At present this BOM is used as a data base to identify the many parts and their codes
in automobile manufacturing companies.
A bill of materials "implosion" links component pieces to a major assembly, while a bill of
materials "explosion" breaks apart each assembly or sub-assembly into its component parts.
A modular BOM can be displayed in the following formats:
A single-level BOM that displays the assembly or sub-assembly with only one level of children.
Thus it displays the components directly needed to make the assembly or sub-assembly.
An indented BOM that displays the highest-level item closest to the left margin and the components
used in that item indented more to the right.
Modular BOM A BOM can also be visually represented by
a product structure tree, although they are rarely used in the workplace.
For example, one them is Time-Phased Product Structure where this diagram illustrates the
time needed to build or acquire the needed components to assemble the final product.For
each product, the time phased product structure shows the sequence and duration of each operation.
Configurable BOM A configurable bill of materials is a form
of BOM used by industries that have multiple options and highly configurable products,
PCs, autos).
The CBOM is used to dynamically create "end-items" that a company sells.
The benefit of using CBOM structure is it reduces the work-effort needed to maintain
product structures.
The configurable BOM is most frequently driven by "configurator" software, however it can
be enabled manually.
The development of the CBOM is dependent on having a modular BOM structure in place.
The modular BOM structure provides the assemblies/sub-systems that can be selected to "configure" an end-item.
While most configurators utilize top-down hierarchical rules syntax to find appropriate
modular BOMs, maintenance of very similar BOMs becomes highly excessive.
A newer approach, utilizing a proprietary search engine scheme transversing through
selectable componentry at high speeds eliminates the Planning Modular BOM duplications.
The search engine is also used for all combinatorial feature constraints and GUI representations
to support specification selections.
To decide which variant of the parts or components are to be chosen, they are attributed by the
product options which are the characteristic features of the product.
If the options of the product build an ideal boolean algebra, it is possible to describe
the connection between parts and product variants with an boolean expression, which refers to
a subset of the set of products.
Multi-Level BOMs A Multi-Level Bill of Materials, or referred
as an indented BOM, is a bill of materials that lists the components, assemblies, and
parts required to make a product.
It provides a display of all items that are in parent-children relationships.
When an item is a sub-component, unfinished part, etc., all of its components, including
finished parts and raw materials, are also exhibited.
A multi-level structure can be illustrated by a tree with several levels.
In contrast, a single-level structure only consists of one level of children in components,
assemblies and materials.
See also Bill of material based on characteristics
Ingredient References
External links BOM template used for PCB assembly – Bill
of materials template used for printed circuit board assembly service.