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186 CHAPTER 6 The Production Process

BOM. Common item categories are stock item, nonstock item, variable-size
item, text item, document item, class item, and intra material.
• A stock item (L) is a material for which stock or inventory is main-
tained; therefore, it must have a material master.
• A nonstock item (N) is one for which inventory is not maintained;
therefore, it does not need a material master defi ned.
• If a material is available in different sizes, such as sheet metal or
fabric, then the different sizes can be represented by the same
material number. In these cases the item category used is variable-
size item (R), and data concerning the needed size or dimension
must be specifi ed in the BOM.
• A text item (T) is used to include notes and comments within the
BOM. Notes may explain how to use the material or identify any
unusual assembly requirements.
• A document item (D) is used to include documents such as engi-
neering drawings, assembly instructions, and photographs.
• Class items (K) are used in variant BOMs to identify a class or
group of items. Companies use variant BOMs to create multiple
versions or variants of the same material rather than prepare a
separate BOM for each version. A class item is a placeholder for
an actual item that must be specifi ed when the BOM is used. For
example, GBI could use a class item to identify the different colors
of frames used in the touring bikes. The specifi c color frame would
then be selected either during production for a production BOM or
during sales for a sales BOM.
• Intra material (M), or phantom items, are a logically grouped set of
materials that could collectively be considered as a single material.
The material is created temporarily during production, between
two subprocesses, and is immediately consumed as production con-
tinues. In the case of GBI, a bicycle always will need two wheels —
a front wheel and a rear wheel. The two wheels could be logically
considered a set, so GBI could use a phantom item to represent
this set.

Business Processes in Practice 6.3: How Large
Can a BOM Be?

The bill of materials for the Boeing 747 includes more checks, and they are inspected multiple times before,
than 6 million parts, half of which are small fasteners or during, and after they are installed. In addition, Boeing
rivets. A 747-400 contains 171 miles (274 km) of wiring must stock more than 6.5 million spare parts in eight
and 5 miles (8 km) of tubing. The body of a 747-400 con- global distribution centers for airlines that need to make
sists of 147,000 pounds (66,150 kg) of high-strength alu- repairs to aircraft that are currently in operation.
minum. To make things even more complex, all those
Source: Boeing Corp.
parts are subject to intensive quality and reliability

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