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Bills of Materials
Part 2 of 2

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Following are the software tools that are needed to support the change to lean bills of material. These tools are located in the item master file, the product structure file, and the logic used with the software system for calculating requirements.

In the item master file, the following data fields are needed:

      Engineering Drawing Number

      Drawing Rev. Level

      Classification Code

     Item Type

     Item Class.

The functionality of these last three data fields must have the capa­bility to be defined by the user instead of being hard-coded within the software.

In the product structure file, the following fields are needed:

     Find number (could be called balloon number, reference number,
ID number, etc.). This is used to relate specific items in the product
structure file to specific elements on a drawing.

     Sequence number. This is used to force a specific and repeatable
sequencing of item numbers from a single level bill of material.

     Operation Used On (could be called first operation used). This is
used to relate each item in the product structure to a specific opera­
tion and/or work cell in the manufacturing process. This is a critical
tool for costing and valuing WIP.

     Lead Time Offset. This allows the timing of due dates to be ad­
justed relative to the overall sequence of production activities. This
prevents a serious timing problem in planning the arrival of pur­
chased items based on purchase commitments.

     Special Codes

-      B=Bulk item. Use of this code allows an item to be excluded on a bill-of-material by bill-of-material basis from transactions and
paperwork requirements but included for costing activities. Some
software sets this code in the item master file.

-      E=Expense item. This code allows items to included in the prod­
uct structure file but not be included in costing activities.

-      R=Reference item. This code is used to identify the drawings,
specifications, test sheets, and other critical documents that must
be provided to support the manufacturing process.

-      T=Tooling. When a component has an extremely small quantity
per usage, this code allow a divisor to be applied to provide the
case by case functionality.

Some of these data fields need specific data handling characteris­tics built into the software coding.

Additionally, the ability to support phantom part numbers with the following software functionality must be verified: Able to assign phantom code in the item master file. Use same parentycomponent relationships as other items. Lead time can be set to 0. Order policy for phantom item must be lot/lot. MRP logic says that if the on-hand balance = 0 then blow-through the parent to the components, if the on-hand balance > 0 then net the requirements for the parent and blow through to the compo­nents for the remainder.


The combination of these bill of material techniques and software tools allows a single bill of material structure to be viewed differently by

several different users of the bill of material data. An example of this is the following structure.

Figure 5 is the actual structure that is in the product structure file.

Figure 6 is the traditional view seen by the engineers. It was cre­ated by sorting the components for the parent (blowing through the phantom parents) into three lists based on the classification code as­signed to each item (mechanical, hydraulic, electrical) within the item master file.

Manufacturing makes the product using two work cells as shown in figure 7. This view was created by sorting the components for the parent (blowing through the phantom parents) based on the operation used on data field from the product structure file. Notice there is no commonality between the views.

Additionally, figure 8 shows how the planning group may see the bills of material based on the forecasting and sales planning activities. This view was created by sorting by sequence number within the phan­tom parents.

Notice that none of the planned and scheduled components were left off or lost between each view. The information was displayed or printed based on the particular requirements of each user.



As more companies are able to take advantage of lean manufacturing techniques, these same companies will need to challenge and maybe even change the way the bills of material process works in their com­panies. Just as manufacturing has adopted techniques that are simpler, which has resulted in a lower cost and faster manufacturing process, the bill of material process is an ideal candidate for simplification. To make these changes happen successfully, the appropriate bills of mate­rial techniques and tools must be understood and available to both plan­ning, manufacturing, and engineering users.


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