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Item Master

The Item Master, sometimes referred to as the Part Master, is at the very core of the company Enterprise Management System. The Item Master contains all of the numbering assignments and descriptive and accounting data for every item the company buys, sells, produces, supports and maintains. This not only includes parts or components, but also numbered assignments for User Manuals, Warranty Cards, Installation Kits, Marketing Brochures, Software and Firmware programs, Training Manuals, Company Procedures, Shipping Materials, Inside and outside labor, Mechanical Drawings, Schematics, Silkscreen Artwork and basically anything else the company has ascribed a value to and wants to track as an inventory or non-inventory type with a location at a standard cost and indicating where it is used, and at what revision. Here is an example of how all of these various items may fit into a process or a Bill of Materials, (BOM).
Beginning with a specific numbered and revision schematic and a subsequent set of Gerbers we can now fabricate a bare printed circuit board. For the sake of example let’s construct a simple indented BOM:

  • 010-00001-001 = Bare PCB
    • S010-00001-001 = Represents the schematic
    • C010-00001-001 = Represents the CAD or Gerber Files

Now let’s go back to the Item Master and examine the assembled PCBA and modify our BOM to nested Version

  • 021-00001-001 = Populated Printed Circuit Board Assembly
    • 010-00001-001 = Same Bare PCB
      • S010-00001-001 = Represents the schematic
      • C010-00001-001 = Represents the CAD or Gerber Files
    • 028-00004-001 = Crystal of a specific value
    • 030-00008-001 = Switch of a specific value
    • 042-00010-001 = Resistor of a specific value
    • 800-00001-001 = Outside Assembly Labor

Now we have a small printed circuit assembly populated with components and included in the BOM, at the same level as the components is the assembly labor cost for the specific board being assembled. This labor cost is picked up from the assembly house quote and included in the Item Master. Now when the cost of a printed circuit card is tallied, the labor is a “component” of the cost. Now we continue to build a higher level assembly and this time we will include Revision indicators.

  • 021-00001-001 Rev 2B = Populated Printed Circuit Board Assembly
    • 010-00001-001 Rev 2B = Same Bare PCB
      • S010-00001-001 Rev B = Represents the schematic
      • C010-00001-001 Rev B = Represents the CAD or Gerber Files
    • 012-00007-001 Rev A = Metal Bracket with insert grommet
      • 012-00007-000 Rev A = Bracket without Grommet
      • 011-00001-001 = .25” O.D. Grommet
      • W500-00000-001 Rev A = Work Instruction Document for attaching the Grommet
    • 028-00004-001 = Crystal of a specific value
    • 030-00008-001 = Switch of a specific value
    • 042-00010-001 = Resistor of a specific value
    • 800-00001-001 = Outside Labor

Now our assembly has grown to include a bracket. In order to build the bracket, it had its own sub assembly including a work instruction on how to affix the grommet to the bracket. We have this work instruction under revision control so when we order the PCBA from the assembly house, they can retrieve the latest revision of the instruction as it shows on the BOM.
Let’s take it up a notch higher to an electromechanical sub assembly that incorporates the PCBA, and an RF shield over the crystal.

  • 131-00004-001= Electromechanical Sub-Assembly with sheet metal with silkscreen pin indicators
    • 012-00009-002 Rev B = silkscreened shield
      • 012-00009-001 Rev B = shield without silkscreen
      • A012-00009-001 Rev A = silkscreen artwork under Revision Control
      • D012-00009-001 Rev B Mechanical Drawing for shield fabrication
    • 021-00001-001 Rev 2B = Populated Printed Circuit Board Assembly
      • 010-00001-001 Rev 2B = Same Bare PCB
        • S010-00001-001 Rev B = Represents the schematic
        • C010-00001-001 Rev B = Represents the CAD or Gerber Files
      • 012-00007-001 = Metal Bracket with insert grommet
        • 012-00007-000 = Bracket without Grommet
        • 011-00001-001 = .25” O.D. Grommet
        • W500-00000-001 Rev A = Work Instruction Document for attaching the Grommet
      • 028-00004-001 = Crystal of a specific value
      • 030-00008-001 = Switch of a specific value
      • 042-00010-001 = Resistor of a specific value
      • 800-00001-001 = Outside Labor

Now if we want to order a shield, we call our fab house and order a 012-00009-002 Rev B and give them the Artwork REV A and the Drawing Rev B each time we order. We do not leave it up to the fab house to retrieve previously used documents. We order the part and include the new documents with revisions reflecting exactly what we want the house to build.

If we go up another level to a Final Assembly, we include the drawings for the enclosure, silkscreen artwork, fasteners, etc. Finally we go to a Finished Goods Level (FG) or Top Level Assembly (TLA) and our BOM includes the shipping carton, Install kits, Documentation to include in the packaging, and any other item that requires cost accounting and becomes a factor in the Cost of Goods Category on Finance;s Chart of Accounts.

The benefit is huge if we include all these items in the Item Master. Now when your forecast to build 150 of a TLA, your MRP system quickly tallies your total cost including all the labor for outside assembly, Direct Labor for inside assembly and testing, and packaging. Also, if all the procedures and work instructions are on the BOM, then the factory line is using the latest instructions to properly produce this product.

The Item Master is where you will get the biggest bang for your buck if you manage it properly. If Drawings, Procedures, and Work Instructions, are checked in and out of Documentation Control and match up with the Rev level indicated on the BOMs, you will have the least amount of unanticipated and unpleasant surprises on the factory floor.

For each Item, at a minimum, the following should be entered into the Part Master System:
Your Company Part Number
The Revision Number or Letter
Type (Part/Assembly/Inventory/Non-Inventory/Labor Inside/Labor Outside)
Standard Cost
Manufacturer’s Name
Manufacturer’s Part Number
Alternate Manufacturer’s Name
Alternate Manufacturer’s Part Number
Make vs. Buy (Make Part will have a drawing)
F.I.T. (Reliability Number)
An Attached Purchasing Specification Document, Supplier Datasheet, Company Document, Technical Drawing (no Rev)

The Item Master must be maintained to ensure absolute integrity as almost every department in the company can be impacted if the wrong revision of a product is made or a wrong part number is soldered to a 150 boards. Imagine what would happen if a bench tech programed 3000 serial proms with an outdated version of the software simply because he couldn’t go on line and query the BOM for the software’s part number and revision for the latest build requirement. More than once, I have seen a source code pulled from a bench computer because the tech thought he or she had the latest version on their system. Again, I cannot overstress the value of proper Documentation Control and the item Master is where it all comes together.

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