Integral Logistics Management — Operations Management and Supply Chain Management Within and Across Companies

7.2.1 Techniques for Standard Products with Few Variants

Intended learning outcomes: Present the conventional variant structure for a few, stockable variants.

A variant bill of material is the bill of material for a product family containing the necessary specifications indicating how the bill of material for a variant of the product family is derived. A variant routing sheet is defined analogously. [note 702].

Standard products with few variants are produced repetitively and possibly stored. Here, conventional representations of product structure using bill of material and routing sheets can be used. Figure shows that a variant in stock corresponds to a different item. Variant-specific compo¬nents are grouped in their own variant assembly, called V1, V2,…, while the general components form their own assembly G. Variants in stock (P1, P2,…) contain as components the general assembly G and the corresponding variant-specific assembly V1, V2,…

Fig.        Conventional variant structure for a few, stockable variants.

The (independent) demand for the product family, weighted by the option percentage, results in the independent demand for variants P1, P2,… The option percentage, like independent demand, is a stochastic variable (see Section 10.5.3). Because of a necessary safety calcula­tion (see Section 10.5.4), the sum of the inde­pendent demand for the variants is greater than the independent demand for the product, or product family. To put it another way, the sum of the option percentages, under consideration of a safety factor, is greater than 1.

In the case of assemble-to-order (ATO), deriving dependent demand for the general assembly G yields an amount that is too large. This is corrected by entering negative indepen­dent demand for general assembly G. This negative number equals the sum of the safety demand for the variants P1, P2,… minus the safety demand for the product family.

This technique is easy to apply to a range of several dozen variants, which can be found, for example, in the manufacture of large machinery. For planning aspects, it may use different kinds of particular bills of material:

  • Both the general assembly G and the variant assemblies V1, V2,… can be phantom assemblies, which are transient (nonstocked) assemblies.

A phantom bill of material represents an item that is physically built, but rarely stocked, before being used in the next step or level of manufacturing (cf. [ASCM22]). [note 703].

  • A position of a variant-specific assembly can also (or partly) represent the subtraction of a position of the general assembly. This can be achieved through a negative quantity per in the variant-specific assembly, for example.

A plus/minus bill of material is a variant bill of material with added and subtracted positions. A plus/minus routing sheet is defined analogously.

  • Both the general assembly G and the variant assemblies V1, V2,… can be — and in particular the “parents” of a plus/minus bill of material are — pseudo items.

A pseudo bill of material is an artificial grouping of items that facilitates planning (ASCM22]).

  • Phantom and pseudo bills of material facilitate the use of common parts bills of material.

A common parts bill of material groups common components of a product or product family into one bill of material, structured to a pseudo parent number (cf. [ASCM22]).

A modular bill of material is arranged in product modules or options. It is useful in an assemble-to-order environment, i.e., for automobile manufacturers (cf. [ASCM22]).

A variant master schedule is a master (production) schedule for products with few variants or product families. [note 704].

Continuation in next subsection (7.2.1b).

Course section 7.2: Subsections and their intended learning outcomes

  • 7.2.2 Techniques for Product Families

    Intended learning outcomes: Present the super bill of material with option percentages x1, x2,…, xn. Describe the production plan and its corresponding MPS at the assembly level, using the example of a product family P with a number of variants in the order of the total demand quantity for the product family.