What is current best practice in part numbering systems?

What is the goal of part numbering system?

The goal of any part numbering system is to uniquely identify the component approved for a specific application. Accurate, consistent, unambiguous part identification is essential for correct product assembly, testing and maintenance.

Part numbering schemes

Typically companies use one of the following types of part numbering schemes and being in the industry for a decade, I have shared common advantages and disadvantages below for all the schemes.

Intelligent – Traditional part numbering systems and document identification schemes originated over 50 years ago. At the time, a basic consideration was that unstructured information was very difficult to find, and it was therefore necessary to overload document identifiers and part numbers with search-related "helper" data.

In other words by looking at the P/N one should be able to have an idea of what the item is. In this case the P/N really becomes the description of the particular part (or assembly) and usually each digit in the Part Number has a particular meaning.

With this type of scheme, a part number generated for a capacitor might be for example  CS-100-03, where “CS” stands for capacitor, “100” is the capacitance in ohm and “003” is the serialized suffix.

There's an almost interesting fascination, with designing the perfect part numbering system. Everyone starts by envisioning how convenient it would be to tell, at a glance, the important characteristics of a part, or the document number that describes the part.

Advantages of intelligent part numbering

Significant part numbers offer time savings downstream, and they can help prevent data entry mistakes and improve manufacturing efficiency. Here’s how:

·         Searching efficiency: With Intelligent part number you can search for and find particular types of parts from just the part number. Searching for *CS* might show you all the capacitors that a company has assigned part numbers to for example. This is really handy if you are designing something and need some particular capacitor in the design. You have to find out if the capacitor you want to use already exists in the company or if you need a new number. By searching on the part number(“CS”) with some wild card characters it’s easy to see where all the capacitors and are they already released

·         Reduction in error: Descriptive part numbers specify the group to which every part belongs, so you can immediately see when a part is in the wrong group.

·         Process improvements: Because parts with similar naming conventions are all handled the same way, you can predefine the change routings, review processes and manufacturing steps for each part number class or category.

Disadvantages of intelligent part numbering

Folks couldn't decide if a washer that was being used to cover a hole in a water tank should be given the P/N for hardware (nut's screws, washers) or should it be given the P/N for hydraulic components (hole plugs, pipe caps, fittings, valves) for example. "it's a flat washer but we are using it as a hole plug, what number does it get?" A group of three or four people standing around for an hour reading and discussing the companies part number system rules and procedures and trying to figure out what the P/N should be for a $1.50 part. Other disadvantages are :

·         Training and knowledge required: Mistakes are often made in encoding the part description into the number, some of which can be quite costly. The engineers who "know the code" use the part number, everyone else reads the part description. If a part's number says "10 amp fuse" while the description is "1.0 amp fuse", a lot of product can get shipped or serviced with the wrong fuse.

·         Error Prone: You can never simply ignore an incorrect part assignment. Otherwise, the category number becomes an unreliable indicator of its content. An aluminum casting that's accidentally assigned to the steel castings category requires an engineering change and full dispositioning. And the error becomes more painful if your number has been cast, engraved, etched or printed on the part. If there are a series of items (O-rings, screw lengths, resistors) with a common base number, one bad part assignment may block a future assignment, and therefore require that the entire series be renumbered.

·         Inefficiencies: You may need a specialist to handle most part numbering if you use a significant scheme. In this case, a single person or group can become a bottleneck. And pulling a part number may require time and discussion, which slows down the design process.

Non-intelligent – On the other side of the battle field is the army of people that say that a Part Number should just be a number, any number, that is just unique to an item and doesn't tell you anything about what the part is. Also referred to as “non-significant.” (not descriptive), all numeric and as short as possible .Non-significant part numbers are typically serial (pulled in numerical order), regardless of the type of part.
Everything has a name and a number associated with it within a company, even the employees. Have you ever cared what the employee number is of a co-worker? Probably not, you are more likely to care about their name. The same logic follows when talking about part numbers in an Insignificant Part Numbering System. The number a particular part has isn't important in an Non-significant Part numbering system, but the description (or name) is. Numbers are usually assigned in numerical order by a specialized computer program like a Product Life Cycle Management (PLM) system. That's the thinking with non-significant part numbers.
Using this part numbering system, a resistor could be assigned part number “P1000012” any unique identifier.

Advantages of non-intelligent part numbering

Using this type of scheme will save your organization time upfront. You can ramp new employees quickly, avoid relying too heavily on any one person and maintain the system without much overhead. Here’s how:

·         Faster to assign: It takes little to no time to pull a sequential number for an item. Assigning a part number can happen fast.

·         Little efforts needed: Easier data migration efforts for legacy to new system. Easier Merger & Acquisition efforts.If your organization hires new employees they will not need to learn how to define a part number and can focus their attention on other tasks. Assigning a new part number can happen with minimal training.

·         Simple maintenance: It is easy to maintain this type of scheme, as it’s essentially a sequential list! You will not have to decide where and how a new part fits into your scheme.

Disadvantages of non-intelligent part numbering

Using a non-significant part numbering scheme isn’t completely error-proof; mistakes can happen, especially if data entry is involved, and managing similar parts can be difficult. Here’s why:

·         Requires a business system to search parts: Because it doesn’t have meaning, a non-significant part number does not provide any cues to help a user evaluate a part. In order to navigate through spreadsheets with randomized part numbers, you need a system that can search for parts based on description, name, size or other relevant attribute .

·         Error prone : With insignificant Part Numbers you have to search in the description field to find all the wire that the company is using. This can be OK if the description fields are all the same, like all wire used in the company has the word "wire" in the description but that isn't always the case. Description fields in most Part Number databases are limited to some small number of characters like 40 for example so the tendency is to abbreviate. "wire" "cable" "condt" "harnss" might all be in the descriptions so if you are looking for wire it might not be that easy to find with Insignificant Part Numbers. Only if strict discipline and rules are established for how to name things can Insignificant Part Number Systems be used successfully

Semi-Intelligent or Hybrid Systems - One way that I have seen this work well is using part category(eg Commodity Codes). Where the business rules are fundamentally coupled to the physical parts. For instance, in the vast majority of cases an "electronic component" number will be quite sufficient, and there's no need to create separate Resistor, Capacitor and Diode commodity code prefixes unless the physical parts are — and always will be — treated quite differently from one another. These parts types, even with separate and unique custom attributes, can all share the same part number format. Since these part categories represent clear and unchanging attributes, you'll want to keep the numbering groups very large.Another way of looking at semi intelligent part numbering system is using class codes to categorize the parts.

Of course, depending on how your company profile and product categories , part numbering system will defer Your business operations can also influence which part numbering system to use. An original equipment manufacturer (OEM) that creates its own part numbers has entirely different business needs than a company downstream in the supply chain.

Also consider your business tools. Will your current system support your part numbering needs? Can you maintain your part number system with your existing tool or will your part number system be more effective by bringing another system into the mix?

Here are some references from experts

 Clement, et al.: Manufacturing Data Structures, page 20:

Another important point about item numbers is that they should be as short as possible. Part numbers are keyed, copied and used as verbal identifiers. The shorter the numbers, the more accurate people can be. Obviously, the greater the number of digits in a part number, the greater chance of error. We also recommend that only numeric digits be used.

Garwood: Bills of Materials: Structured for Excellence, page 73 (author's emphasis):

The solution...is to use shorter non-significant part numbers. We have found that part numbers of 5 or 6 digits are the most effective.

Watts: Engineering Documentation Control Handbook, page 49:

The most critical of these issues is that, over time, the significant numbering systems tend to break down. ... As time passes, variations arise which were not foreseen. One digit was set aside where two are now needed. Significant numbers thus tend to lose their significance. They no longer do the classification coding function intended by their inventors.

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