A bill of materials (also known as a BOM or bill of material) is a comprehensive list of parts, items, assemblies and other materials required to create a product, as well as instructions required for gathering and using the required materials. The bill of materials can be understood as the recipe and shopping list for creating a final product. The bill of materials explains what, how, and where to buy required materials, and includes instructions for how to assemble the product from the various parts ordered. All manufacturers building products, regardless of their industry, get started by creating a bill of materials (BOM).

Because the bill of materials pulls together all sorts of product information, it is common that several disciplines (design and engineering, document control, operations, manufacturing, purchasing, contract manufacturers and more) will consume data contained within the BOM record to get the job done right. In fact, engineers and manufactures rely so heavily on BOMs they their own special subsets called the engineering bill or materials (EBOM) and the manufacturing bill of materials (MBOM). The BOM guides positive results from business activities like parts sourcing, outsourcing and manufacturing, so it is important to create a BOM that is well organized, correct and up to date.

And for companies that outsource manufacturing activities, it is especially important to create an accurate and revision-controlled bill of materials. Any time the BOM is handed off to a contract manufacturer (CM) or supplier, it should be correct and complete, otherwise you can expect production delays.

Because one of the main functions of the BOM is to ensure that the product is built right, it is best to include specific pieces of product data in the BOM record. Hereinafter, I share with a BOM document includes the following information:

• Level (LVL): A single digit which indicates on what level of the BOM the part resides.
• BOM ID: This number uniquely identifies a particular line within your BOM.
• Part No.: The part or assembly identification number.
• Description: Name or short description of the particular part or assembly.
• Revision (REV): The revision level of the particular part or assembly.  Typically, only used for parts you design.
• Quantity (QTY): The numerical quantity required of a part or assembly, or, depending on the unit of measure, the precise amount of a material required.
• Unit of Measure (UOM): Typically, this is EACH for individual parts or assemblies, but for certain items (e.g. tape, grease, insulation, etc.) a specific unit is used instead.
• Supplier: The specific vendor who will supply the part, if purchased.
• Supplier Part No.: The specific vendor's own internal part number if it differs from what is shown in PART NO.
• Material: Raw material specification for newly manufactured parts.
• Finish: Field to specify any material finishes, heat treatments, or other processes to be applied to the part.

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Creating a bill of materials is not only a necessary step in the product development process, it is also what makes your product design a reality. Before you create a BOM record, it is important to consider who will utilize the information and how you will maintain and manage all associated product documentation like part datasheets and CAD files. Develop more efficient manufacturing practices by capturing detailed part information when creating a bill of materials.

This terminology includes terms, definitions of terms, descriptions of terms, nomenclature, and acronyms associated with additive-manufacturing (AM) technologies in an effort to standardize terminology used by AM users, producers, researchers, educators, press/media and others.

The subcommittee responsible for this standard will review definitions on a three-year basis to determine if the definition is still accurate as stated. Revisions will be made when determined to be necessary.

This table contains the obtained values of machining tolerance and surface roughness according to the machining or cutting process, these process collectively termed as "material removal processes".

The process (table order):
1- Electro-Discharge Wire Cutting.
2- Band Sawing.
3- Circular Sawing.
4- Cropping / Guillotining.
5- Sheet Metal.
6- Water Jet Cutting.
7- Oxyfuel Gas Cutting.
8- Plasma Arc Cutting.
9- Chemical Machining.
10- Chemical Polishing.
11- Electro-Chemical Machining.
12- Electro-Discharge Machining.
13- Electron Beam Machining.
14- Electropolishing.
15- Abrasive Jet Machining.
16- Abrasive Grinding / Polishing.
17- Broaching.
18- Drilling.
19- Honing.
20- Lapping.
21- Millimg (CNC).
22- Milling (Manual).
23- Planing / Shaping.
24- Reaming.
25- Turning / Boring (CNC).
26- Turning / Boring (Manual).
27- Ultrasonic Machining.
28- Laser Beam Machining.

The standard ISO DIN 2768 is a standard has been issued by the International Organization for standardization - ISO in association with Deutsches Institut für Normung - DIN. This standard determines the general tolerance values for the untoleranced linear and angular dimensions and also for the form and position tolerances. It's used to simplify the engineering drawings in case of determining the mechanical tolerances for parts' dimensions which are manufactured by machining means.
This standard consists of two sub-standards:

1- ISO DIN 2768-1 Standard:
This sub-standard determines the values of general tolerances of the linear and angular dimensions and radius of curvature and chamfer height according to four classes of levels: f (fine), m (medium), c (coarse), v (very coarse).

2- ISO DIN 2768-2 Standard:
This sub-standard the values of general tolerances in regard of form and posistion according to three classes or levels: H (fine), K (medium), L (coarse).

In engineering drawings, and for the untoleranced dimensions, the medium level is usually used ( "m" for the first sub-standard and "k" for the second sub-standard), and that can be expressed by writing the following in the title box: ISO DIN 2768 - mK.