Bill of materials

Last updated April 16, 2024

An example of a BOM for a mechanical assembly (in German) Schneckengetriebe.png — An example of a BOM for a mechanical assembly (in German)

A bill of materials or product structure (sometimes bill of material, BOM or associated list) 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 bill of materials is often tied to a production order whose issuance may generate reservations for components in the bill of materials that are in stock and requisitions for components that are not in stock.

A BOM can also be visually represented by a product structure tree, although they are rarely used in the workplace.^[1] For example, one of them is Time-Phased Product Structure^[2] 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.

Structure

BOMs are of hierarchical 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.

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.

Usage

In process industries, the BOM is also known as the formula, recipe, or ingredients list. The phrase "bill of material" (or "BOM") is frequently used by engineers attributively to refer not to the literal bill, but to the current production configuration of a product, to distinguish it from modified or improved versions under study or in test.

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 the component engineer who will procure the components required for the design.

Types

A BOM can define products as they are designed (engineering bill of materials), as they are ordered (sales bill of materials), as they are built (manufacturing bill of materials), or as they are maintained (service bill of materials). The different types depend on the business need and use for which they are intended.

Sometimes the term "pseudo-bill of materials" or "pseudo-BOM" is used to refer to a more flexible or simplified version. Often a place-holder part number is used to represent a group of related (usually standard) parts that have common attributes and are interchangeable in the context of this BOM.^[3]

A modular BOM (or variant parts list) can be displayed in the following formats:

A single-level BOM (or unit list) 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 (or structural parts list) that displays the highest-level item closest to the left margin and the components used in that item indented more to the right.^[1]
Modular (planning) BOM

A single-level BOM resolved to list the effectively needed quantities of components to produce a product (rather than to list each individual part by its logical name) is also called quantity synopsis parts list.^[4]

Configurable BOM

A configurable bill of materials (CBOM) is a form of BOM used by industries that have multiple options and highly configurable products (e.g. telecom systems, data-center hardware (SANS, servers, etc.), PCs, cars).^[5]

The CBOM is used to dynamically create "end-items" that a company sells. The benefit of using CBOM structure is that 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 (manual maintenance is infrequent because it is unwieldy to manage the number of permutations and combinations of possible configurations). 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 (i.e., only one component is different for various voltages) becomes highly excessive. A newer approach, (bottom-up/rules-based structuring) utilizing a proprietary search engine scheme transversing through selectable componentry at high speeds eliminates the planning modular BOM duplications.^{[ citation needed ]} The search engine is also used for all combinatorial feature constraints and GUI representations to support specification selections.

To decide which assembly variant of the parts or components is 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,^[6] it is possible to describe the connection between parts and product variants with a Boolean expression, which refers to a subset of the set of products.^[7]^[8]^[9]

Parts which will not be assembled at all in one or more variants are typically marked as "DNP" (for "do not populate" or "do not place") in the affected variants. Other less frequently used designators for this include "NP" ("no placement", "not placed"), "NF" ("no fit", "not fitting"), "DNM" ("do not mount"), "NM" ("not mounted"), "NU" ("not used"), "DNI" ("do not install", "do not insert"), "DNE" ("do not equip"), "DNA" ("do not assemble"), "DNS" ("do not stuff"), "NOFIT" etc.^{[nb 1]}

Multi-level BOM

A multi-level bill of materials (BOM), referred to as an indented BOM, is a bill of materials that lists the assemblies, components, and parts required to make a product in a parent-child, top-down method. It provides a display of all items that are in parent-children relationships. When an item is a sub-component, of a (parent) component, it can in-turn have its own child components, and so on. The resulting top-level BOM (item number) would include children; a mix of finished sub-assemblies, various parts and raw materials. 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 material.

Notes

↑ The abbreviation "NB" or "n.b." (for nicht bestücken) is commonly used in German-speaking countries.

Related Research Articles

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Mass customization makes use of flexible computer-aided systems to produce custom products. Such systems combine the low unit costs of mass production processes with the flexibility of individual customization.

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Product data management (PDM) is the name of a business function within product lifecycle management (PLM) that denotes the management and publication of product data. In software engineering, this is known as version control. The goals of product data management include ensuring all stakeholders share a common understanding, that confusion during the execution of the processes is minimized, and that the highest standards of quality controls are maintained. PDM should not be confused with product information management (PIM).

Prefabrication is the practice of assembling components of a structure in a factory or other manufacturing site, and transporting complete assemblies or sub-assemblies to the construction site where the structure is to be located. Some researchers refer it to “various materials joined together to form a component of the final installation procedure“.

Design for excellence is a term and abbreviation used interchangeably in the existing literature, where the X in design for X is a variable which can have one of many possible values. In many fields X may represent several traits or features including: manufacturability, power, variability, cost, yield, or reliability. This gives rise to the terms design for manufacturability, design for inspection (DFI), design for variability (DfV), design for cost (DfC). Similarly, other disciplines may associate other traits, attributes, or objectives for X.

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Modular design, or modularity in design, is a design principle that subdivides a system into smaller parts called modules, which can be independently created, modified, replaced, or exchanged with other modules or between different systems.

An engineering bill of materials (EBOM) is a type of bill of materials (BOM) reflecting the product as designed by engineering, referred to as the "as-designed" bill of materials. Some parts of BOM includes "Contengency Fund" an emergency fund when the as-designed materials shortage happened, inflation of materials are included if and only if. The Contractor Profit is the transparent Profit the Contractor or direct Engineer will receive at rural areas when the project is finished. The Manpower fund commonly called the Labor fund is also included in the BOM, these fund are commonly returned to the project owner when it excess as per as-designed BOM.

Product structure is a hierarchical decomposition of a product, typically known as the bill of materials (BOM). As business becomes more responsive to unique consumer tastes and derivative products grow to meet the unique configurations, BOM management can become unmanageable. For manufacturers, a bill of materials (BOM) is a critical product information record that lists the raw materials, assemblies, components, parts and the quantities of each needed to manufacture a product.

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Engineer to order is a production approach characterized by:

Engineering activities need to be added to product lead time.
Upon receipt of a customer order, the order engineering requirements and specifications are not known in detail. There is a substantial amount of design and engineering analysis required.

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The guideline committee VDI 2343 "Recycling of electrical and electronic devices" was initiated in 1996 by Ralf Brüning. The aim is to develop practical and legally compliant recommendations for action in order to support the affected groups in their work, for expample disposal companies, manufacturers, universities, authorities, lawyers, environmental associations, reuse companies. Thereby among other things the aspects of logistics, dismantling, processing, recycling and reuse are dealt with in seven sub-committees and coordinated in an overall committee.

References

1 2 Reid, R. Dan; Sanders, Nada R. (2002). Operations Management. John Wiley & Sons. pp. 457–458. ISBN 0-471-32011-0.
↑ Malakooti, Behnam (2013). Operations and Production Systems with Multiple Objectives. John Wiley & Sons. ISBN 978-1-118-58537-5.
↑ "pseudo bill of material". BusinessDictionary.com. Archived from the original on 2020-08-05. Retrieved 2018-04-17.
↑ Hochheimer, Norbert (2011). Das kleine QM-Lexikon: Begriffe des Qualitätsmanagements aus GLP, GCP, GMP und EN ISO 9000 (in German). John Wiley & Sons. p. 277. ISBN 978-3-52733076-8 . Retrieved 2022-04-04. (334 pages)
↑ "Super BOM". SAP ERP 6.0. SAP. 2012. Archived from the original on 2013-02-17. Retrieved 2012-07-17.
↑ Herlyn, Wilmjakob Johannes (2012). PPS im Automobilbau – Produktionsprogrammplanung und -steuerung von Fahrzeugen und Aggregaten[PPS in automobile engineering – Production program planning and control of vehicles and assemblies] (in German). Munich, Germany: Carl Hanser Verlag. ISBN 978-3-446-41370-2.
↑ Herlyn, Wilmjakob Johannes (January 1990). Zur Problematik der Abbildung variantenreicher Erzeugnisse in der Automobilindustrie [On the problems of mapping high-variation products in the automobile industry]. Fortschritt-Berichte VDI, Reihe 16: Technik und Wirtschaft (in German). Vol. 52. Düsseldorf, Germany: VDI Verlag. ISBN 3-18-145216-5. ISBN 978-3-18-145216-5 . Retrieved 2021-01-29. (127 pages)
↑ Paul, Matthias R. (2012-01-20) [2005]. "Eine durch den Nutzer erweiterbare Klammer-Präfix-Notation zur flexiblen Definition und Verwaltung von Bestückungsvarianten durch Auflösung logischer Bedingungen". BOM-MPL (Program documentation). 1.06 (also 1.09 as of 2013-03-04) (in German). Retrieved 2012-02-05. (NB. A ULP-based BOM management tool for the EDA tool EAGLE 5 to 7 with support for part databases and EAGLE's assembly variants and attributes in addition to a more flexible system based on parentheses notation stored as prefixes to part values defining multi-level logical conditions and dependencies of assembly groups and possible alternative part values. Originally devised by the author as an easy-to-understand symbolic notation assisting a user manually processing variant BOMs before CadSoft added support for variants and attributes to EAGLE, it was later integrated into the author's BOM tool for automatic variant management.)
↑ Frischen, Christian; Marbach, Anastasia; Tichla, Florian; Mantwill, Frank (2019-09-18). Written at Hamburg, Germany. Krause, Dieter; Paetzold, Kristin; Wartzack, Sandro (eds.). "Durchgängige Variantensteuerung mit Hilfe der regelbasierten Komplexstückliste". DS 98: Proceedings of the 30th Symposium Design for X (DFX 2019). DfX (in German and English). Jesteburg, Germany: Mechanical Engineering & Computer-assisted Product Development, Helmut-Schmidt-Universität: 13–24. doi: 10.35199/dfx2019.2 . Archived from the original on 2021-03-27. Retrieved 2021-03-28. (12 pages)