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Document Numbers

Quality Management System

Numbering your documents

It is not a specific requirement of the ISO 9001 or any other standard to uniquely identify a part or a document. It is more a common-sense measure, and a worldwide practice in any documentation system, to give a document or a component a number and a title, and to identify its revision level. As documentation titles, document numbering is an area for creativity and an opportunity for optimization.

Once I worked with a company of less than 100 people, manufacturing fairly simple devices. Their documentation system consisted of a few numeration systems depending on the type of document. One of the procedures had a number 0000057-001, which they simply called “fifty seven.” A drawing was numbered 327-856-99-17. Some companies obviously want to feel like the “big boys.” If numbers are long and complicated, one might think that they make complex and important products.

Is it acceptable to have long and difficult-to-read and remember numbers? Yes, of course! Is it practical? I do not believe so! In the example above, the procedure numbers, without the tab, contained seven digits. This meant that the system was prepared to handle almost 10 million part numbers (PN). The company had approximately 250 documents and probably would never go beyond 300. If nothing else, just reading these numbers with five sequential zeros may give one a headache. Those folks figured it out too - that is why they called document 0000057-001 “fifty seven.” Surprisingly, this is not the worst case I have experienced! The company that won my “The Worst Part Number” Grand Prize assigned 12 (!) digits to their part numbers in alphanumeric format.

If you are designing and building a Trident-class submarine, a MIG-27 jet fighter or an international space station, you, most likely, will need millions of parts, so a long part number format would be needed and will make sence. Otherwise, save yourself the trouble of reading all those zeros and make your numbering system practical. Our Documentation Management Procedure shown in Chapter 3 prescribes part numeration with a four-digit part number format that allows for 9,999 parts, which is probably enough for majority of companies. If your operation is small, drop it to three digits – you may always change it later if you need to. One of my customers, who won my “the Best Part Number” Grand Prize, numbered their documents as 201, 202, 203, and so on. Short and sweet!

Another issue with the part-numbering format is part number designation. Some systems associate a part number with a particular part type. For example, 10xxx indicates a procedure, 20xxx indicates a drawing, PLxxx indicates a policy-level document, and so on. An alternative approach to part numbering is a “no designation” system, where parts are given sequential unique numbers within a specified format, regardless of their type, material, application or other attributes. After all, isn’t the part title the best designator?

My experience with a number of medical device manufacturers has convinced me in the benefits of a “no designation” system. Three designation systems I have worked with have failed. Just recently, one of my customers reported that they ran out of range in their part-numbering format. The system allowed for assigning materials through a two-digit designator within the part number. When the system was designed, needing more than 99 materials was not considered possible. Unfortunately, things changed, and just a few years later, the company needed more than 99 materials causing the existing part number format to fail.

An overwhelming majority of companies use designation-based part-numbering systems. A Design Management Procedure, for example, may be numbered as SOP 4.4-1. With the previous revision of the ISO 9001 standard, it meant that this document related to the element 4.4, design management. Well, it does not mean the same with the new ISO 9001 revision, simply because design management clause now has a different number: 7.3. What is the solution? The solution is simple: no part numbers, and no designators!

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