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

17.2.3 Bill of Material, Bill-of-Material Position, Where-Used List, and Where-Used-List Position

Intended learning outcomes: Present the concepts of the bill of material and of the bill-of-material position, the where-used list, and the where-used list position. Differentiate between the single-level bills of material, the multilevel bill of material, and the summarized bill of material. Differentiate between the single-level where-used list, the multilevel where-used list, and the summarized where-used list. Describe the bill-of-material position logistical object and its most important attributes.



By way of example, Figure 1.2.2.2 shows a bill of material, that is, a convergent product structure with two structure levels. The conventional method used to model the bill-of- material business object does not represent the object as a whole. Instead, it defines a detailed logistical object for that business object.

A bill-of-material position is a product <-> component connection within a bill of material.

Here is an example. Figure 17.2.3.1 contains five items — the three components x, y, and z, each of which occurs in products 1 and 2.

Fig. 17.2.3.1       Representation of two bills of material, each with three components.

The two bills of material lead to detailed objects, that is, six bill-of-material positions. These represent the six connections shown in Figure 17.2.3.2 from the product viewpoint and from the component viewpoint.

Fig. 17.2.3.2       Detailed logistical objects: the six bill-of-material positions as connections in two bills of material, each with three components.

Breaking down bills of material into their individual positions leads directly to further logis­tical objects. They are all derived from the bill-of-material positions by means of algorithms.

A where-used list indicates the way in which a component is used in different products, taking the structural levels into account (see Section 1.2.2).

The component viewpoint in Figure 17.2.3.2, that is, the bottom to top viewpoint in Figure 17.2.3.1, leads to three where-used lists — for the components x, y, and z, each with two uses in products 1 and 2.

Different forms of these bills of material and where-used lists are needed, depending on the application. Each “product « component” connection should only be defined or stored once, however. The only exception to this rule is for components that occur several times in the same product (but are different each time). These occurrences can be differentiated using a relative position number (see below).

A single-level bill of materialshows all the components of a product.

Figure 17.2.3.3 shows the three single-level bills of material, each with two bill-of-material positions, as implicitly defined by the example in Figure 1.2.2.2.

Fig. 17.2.3.3       Single-level bills of material.

The multilevel bill of material or indented bill of material shows the structured composition of a product, across all the levels.

Figure 17.2.3.4 shows the indented bill of material for the example in Figure 1.2.2.2.

Fig. 17.2.3.4       Indented bill of material (multilevel bill of material).

In this form, the content corresponds exactly to the graphical represen­tation of a product as a tree structure, again as shown in Figure 1.2.2.2.[note 1703] The quantity per is always the cumulative quantity of the component used at this point in the product (by way of contrast to the graphical form in Figure 1.2.2.2).[note 1704] An algorithm can also be used to generate a multilevel bill of material from the single-level bills of material.

The summarized bill of material is a condensed multilevel bill of material in which each component occurs only once, although the total quantity per is specified.

Figure 17.2.3.5 shows the summarized bill of material for the example in Figure 1.2.2.2.

Fig. 17.2.3.5       Summarized bill of material (condensed multilevel bill of material).

The quantity per is the cumulative quantity of components used in the product. A summarized bill of material is used for manual cost estimating or for quickly calculating the number of components to be bought for a lot of end products. A summarized bill of material can also be generated from the single-level bills of material using an algorithm.

Similar algorithms can also be used to create various types of where-used lists from the bill- of-material positions.

The single-level where-used list shows all the products that are integrated directly into a component.

Figure 17.2.3.6 shows the five single-level where-used lists implicitly defined by the example in Figure 1.2.2.2.[note 1705]

Fig. 17.2.3.6       Single-level where-used list.

Figure 17.2.3.6 contains exactly the same number of connections as Figure 17.2.3.3, that is, six. Although these are the same connections, here they are taken from the component view in Figure 17.2.3.2. In this case, the quantity per is the quantity of components integrated directly into the product. The single-level where-used list is useful because it provides a picture of a certain component.

The multilevel where-used listor indented where-used list shows, in structured form, how a component is used across all the levels, right down to the end products.

Figure 17.2.3.7 shows the multilevel where-used list for the component with item ID 387462 from the example in Figure 1.2.2.2.

Fig. 17.2.3.7       Indented where-used list (multilevel where-used list).

Here, the quantity per is the cumulative quantity of this component that is integrated into the product at this point. An indented where-used list is useful for assessing the possible consequences of a substitution, that is, the replacement of an unavailable primary product or component by a non-primary item.

The summarized where-used list is a condensed multilevel where-used list in which each product occurs only once, together with the cumulative quantity of that component incorporated into the product.

Figure 17.2.3.8 shows the summarized where-used list for the component with item ID 387462 from the example in Figure 1.2.2.2.

Fig. 17.2.3.8       Summarized where-used list (condensed multilevel where-used list).

In this case, the quantity per is the total quantity of components that are integrated into the product. A summarized where-used list is needed to draw up a procurement plan, for examp­le, or to estimate which end products will be affected by replacing an item at a lower level.

The bill-of-material position logistical object appears in the type of formalized product structure shown in Figure 17.2.3.9.

Fig. 17.2.3.9       The bill-of-material position logistical object.

The left-hand side of Figure 17.2.3.9 shows the content of Figure 17.2.1.3, as shown in Figure 1.2.2.1. The item class is thus in an n-to-n association with itself.

  • A product may have different components. Expressed formally, this means that an object of the item class, in its specialization as a product, consists of n different objects from the item class, component specialization.
  • A component may occur in different products. Expressed formally, this means that an object of the item class, in its specialization as a component, is used in n different objects from the item class, product specialization.

This n-to-n association is then shown on the right-hand side of Figure 17.2.3.9, broken down into the two corresponding 1-to-n associations. This results in an additional object class, namely, the bill-of-material position, which determines the “product « component” connection or association between two items. This association may be either “item, as a product, consists of” or “item, as a component, is used in,” depending on which side we start with. A bill-of-material position is thus simultaneously a where-used list position.

The where-used list position is a different view of the bill-of-material position.

The view of the bill of material can be described as follows:

  • All n bill-of-material positions can be reached from a product, and all these positions lead to a component that is built into the product. Taken together, all these positions with the information they contain on the component form the bill of material.

The view of the where-used list can be described as follows:

  • All n where-used list positions can be reached from a component, and all these positions lead to a product in which the component is used. Taken together, all the positions of the where-used list with the information they contain on the product form the where-used list.

The most important attributes that have to be administered for a bill-of-material position are:

  • Product ID (the product identification); this is an item ID
  • Component ID (the component identification); this is an item ID
  • Quantity per, that is, the number or quantity of components that is needed to produce a single unit of the product
  • Sequential number of the position within the bill of material (for sorting and identification purposes)
  • Operation ID for which the component is needed (see Section 17.2.6)
  • Lead-time offset, that is, the difference in time relative to the product completion date before which the components must be made available (see Section 1.2.3)
  • Effectivity (dates) or effective dates (start and stop), that are the dates on which a component is to be added or removed from the bill of material; effectivity control may also be by engineering change number or serial number rather than date

Again, these are only the most important attributes for the elementary functions associated with the bill of material and where-used list. Additional attributes and even additional logistical objects must be represented for more complex applications, for example, bills of material for a product family with many variants. See also Chapter 7 and Section 17.3.

In historic and generic terms, the bill-of-material position ID (bill-of-mate­rial position identification) combines the product ID and component ID attributes. Today, it is more often the union of the product ID and sequen­tial number of the position within the bill-of-material attributes, however.

The advantage of the second definition is that the same component can occur more than once in the same bill of material. The components may also be sorted into a logical order that does not correspond to the component ID. This does have the disadvantage that the number of possible components of a product is limited by the number of possible relative position numbers. In addition, to keep a certain degree of order, any “holes” must be filled in the order of relative position numbers. This can be done by first allocating every tenth number and then periodically reorganizing the numbering.

Aspects of computerized administration:

  • Certain transactions enable whole or partial bills of material for one assembly to be copied to another assembly. There are also transactions that allow large-scale modi­fications to be carried out, e.g., by replacing a certain component with a different component in every bill of material (batch procedure running in background mode).
  • Another algorithm periodically calculates the low-level code of all items. It can also check whether a multilevel bill of material is actually a product structure without loops. This test is often rather time consuming and is difficult to carry out online while administering the bills of material. See also Section 8.3.3.



Course section 17.2: Subsections and their intended learning outcomes

  • 17.2 The Master Data for Products and Processes

    Intended learning outcomes: Describe master data of products, product structure, components, and operations. Explain the data structure of item master, bill of material, and where-used list. Disclose the data structure of work center master data, the work center hierarchy, as well as for operation, routing sheet, production equipment, bill of production equipment, and bill of tools.

  • 17.2.1 Product, Product Structure, Components, and Operations

    Intended learning outcomes: Present the concept of master data. Explain the production order as a collection of master data. Describe a simple product structure. Identify the intermediate product used simultaneously as a component in higher-level products.

  • 17.2.2 Item Master Data

    Intended learning outcomes: Present the concept of the item master record. Describe the attributes of the technical information and the stockkeeping information of the item master record. Identify attributes of the item master record for information on costs and prices.

  • 17.2.3 Bill of Material, Bill-of-Material Position, Where-Used List, and Where-Used-List Position

    Intended learning outcomes: Present the concepts of the bill of material and of the bill-of-material position, the where-used list, and the where-used list position. Differentiate between the single-level bills of material, the multilevel bill of material, and the summarized bill of material. Differentiate between the single-level where-used list, the multilevel where-used list, and the summarized where-used list. Describe the bill-of-material position logistical object and its most important attributes.

  • 17.2.4 Work Center Master Data

    Intended learning outcomes: Present the work-center business object. Describe the attributes of the work-center master record relating to capacity, concerning costs, and for calculating the lead time.

  • 17.2.5 The Work Center Hierarchy

    Intended learning outcomes: Present the concepts of workstation and cost center. Explain the work center hierarchy.

  • 17.2.6 Operation and Routing Sheet

    Intended learning outcomes: Present the concepts of the operation business object in association with the routing sheet. Describe the most important attributes of the operation master object. Produce an overview on the work center where-used list.

  • 17.2.7 Production Equipment, Bill of Production Equipment, and Bill of Tools

    Intended learning outcomes: Present the concepts of bill of production equipment and bill-of-production-equipment position as well as production equipment where-used list. Produce an overview on collective tool, bill of tools, bill-of-tools position, and tool where-used list.

  • 17.2.8 Composition of the Basic Master Data Objects

    Intended learning outcomes: Explain the breakdown of the master data into individual classes and their associations using the example of the ball bearing. Describe the basic object classes for planning & control.