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Michael Roman - Wednesday, March 12, 2014

In Honor of Don Frank, CFPIM, CIRM

In 2004, when Manufacturing Practices, Inc. began, I once again called on Don Frank, CFPIM, CIRM a mentor and dear friend for guidance and joint business opportunities.  We began working on a book and several seminars to help focus the book.  Unfortunately, Don’s health very rapidly failed and I lost him to the ages.  He wrote this piece several years earlier and delivered it at an Atlanta APICS dinner meeting in the 1990s.  He told me to use it when the time was right.  After engaging in a recent discussion on LinkedIn about Part Numbering schemes, this seems the appropriate time.


Let’s go back to basics when we talk about part number attributes.

  • First, part numbers are the data elements or objects that enable us to separate each part from all others as we, in design and operations management, communicate information to each other.
  • Second, the part number enables us to access all the data elements associated with any part in our systems, validating its uniqueness and ensuring we are processing the part we intended. 
  • Third, a part number, assigned to a document, such as an inspection or test report, should appear on bills of material. 
  • Fourth, construct the part number in the simplest lean manner—a pure, sequential numeric form. A good rule for part number length is to add one digit more than the maximum conceivable  number of parts that will ever be in the system. With just eight digits, we can define 99 million unique parts!

People who object to this principle are mostly holdovers from punch card days when, because of the space limitations on the cards, putting intelligence into part numbers.  That perception was the thought that it is necessary for part recognition. Experience, which goes back more than 50 years, was that, even with the limitation of 78 usable columns in a punch card, we could rely better on good part descriptions, rather than remembering the part number, to communicate for what the part number stood.

One of the lessons learned early was to make the part number and drawing number identical, saving a critical amount of space in the part record and making configuration management via revision codes much simpler. We increased the length of the part number to 10 characters, left justified, with the format nnnnnn-nnn, where the first digit represented the drawing size (1 for A size, 2 for B size, etc., so we knew where the drawing was filed). The dash and last three digits we reserved for use with tabulated drawings where several parts represented on the same drawing. An example of this was a set of heat sinks, all made from the same extrusion, but with different lengths, hole patterns, and inserts.

Today's part master databases, with a hundred or more data elements or objects associated with any part master record, enable us to find and visually determine the uniqueness of each part right at the workstation. Original drawings are most often digitally stored rather than on paper. String searches are quick and effective, zeroing in on the part in question in a matter of milliseconds. Just clicking on the part number gives access to all the needed information. We can even hyperlink to a 3-D drawing of the part if necessary.

Highly visible good descriptions will eliminate any excuse for the extra non-value-added task of establishing and maintaining part number coding systems. Descriptions should have two segments—a generic standardized family word description followed by a modifier that differentiates each of the parts in the family. Examples: stainless steel passivated cross-recessed machine screw 10-32 x 1; film fixed resistor 1200 ohm ½ watt 1%.

The first exercise in standardizing part descriptions resulted in reducing the number of parts to support the master schedule from about 5,000 to about 450. The cost savings actually paid for the budding inventory management system.

Another lesson learned was never to use the supplier’s part number as the internal part number because it is too restricting. If you have to change supplier or add an alternate, you create another part number even though the parts are truly interchangeable. Today’s systems allow multiple entries of supplier, supplier part number, and even supplier price against any part number.

Finally, there is still a huge configuration management gap out there because engineering mindsets and product lifecycle management part master data use revision code, and our enterprise resources planning systems use effectivity by date, lot, or serial number.

Here is a word of caution. Do not arbitrarily change existing part numbers when upgrading or implementing new information systems. There is too much engineering, marketing, sales, customer, and supplier documentation out there with embedded legacy part numbers to justify making this type of non-value-added change. Set up a dual-key (alias) system so the system can respond to either old or new part numbers. However, do not allow the sins of the past to perpetuated in newly generated part numbers—use the simple, numeric, and sequential scenario.

Frankly, the only reason we have to put up with long, heavily coded part numbers today is tradition. All new parts generated should have simple, short numeric part numbers. After all, it only takes at most eight digitsto create 100,000,000 Part Numbers! Lean thinking demands we take this approach to intelligent part numbering.

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