The Art of a Good Custom Part Number (CPN) Scheme

March 20, 2023


In today’s fast-paced and highly competitive market, hardware organizations must have efficient engineering processes to stay ahead. One such process is the management of a part number system, a critical piece of hardware product development and production.

Developing an effective part numbering system is not as simple as assigning random numbers or letters to parts. It requires a systematic approach that considers your unique needs and business processes.

This article explores two part numbering scheme options which serve as two extremes across a spectrum of options. Duro recommends that product development companies go for a balance of the two and we’ll explain why in this article.

What is a part numbering scheme?

A part number is a unique identifier assigned to a discrete component defined within the BOM (Bill of Materials) of a product. A part number helps keep track of the components of the BOM throughout their entire lifecycle, from design to production to maintenance.

Part numbers should adhere to a specific part numbering scheme. The part numbering scheme is what drives the rules of the overall part numbering system that a company may choose to adopt. Every hardware company is entitled to design a part numbering scheme that best fits the characteristics of their own products and processes. But it’s crucial to think it through properly and design a scheme that won’t lead to mistakes in production.

When designing, or selecting, a part numbering scheme here are the two extremes that hardware companies often consider, with many acceptable variations in between.

Intelligent part numbering schemes

An intelligent part numbering scheme typically contains alphanumeric strings where each character has a significance and meaning, usually tied to the parametrics and usage of the part. The characters may be associated with a part category, the type of part, the manufacturing process, and more.

This approach allows part details and attributes to be quickly identified and sorted based on their characteristics, making it easier to identify and manage complex products and assemblies.

Pros of an intelligent part numbering system

  • Facilitates easy data retrieval: Using codes and identifiers in an intelligent part numbering system makes searching and retrieving parts from the database easier and more accessible because of each unique part’s codes and identifiers.
  • Reduces the risk of errors and duplicate entries: An intelligent part numbering system reduces the risk of errors and duplicate entries. Since each part is assigned a unique identifier or code, there is less of a chance of mistakenly inputting incorrect part numbers. This can save time and reduce costs associated with rectifying errors.
  • Allows better readability: Intelligent part numbers tend to contain a coded structure that provides for easy identification of the part or assembly. With an understanding of what each coded segment of the part number refers to, team members can quickly identify and understand which part or assembly the part number refers to.

Cons of an intelligent part numbering scheme

While there are several advantages to using an intelligent numbering scheme, there are also some potential drawbacks to consider. Here are a few cons to keep in mind:

  • Limited scalability: One of the main challenges with an intelligent part numbering scheme is that scaling the system can be difficult. As you add new parts or components, you may need to modify the existing system, which can be time-consuming and expensive.
  • Increased complexity: An intelligent numbering scheme can be more complex than a simple sequential or random numbering system. This can make it harder for new team members to understand and use the system effectively, leading to errors or delays.
  • Reduced flexibility: Once you have established an intelligent numbering scheme, making changes or adapting to new requirements can be challenging. As a result, you may be locked into using a system that is no longer optimal for your needs.

When to use an intelligent scheme

While an intelligent numbering scheme may not be the right choice for every organization, there are several situations where it can be highly effective. Here are a few scenarios where an intelligent numbering scheme could be a wise choice:

  • Large and complex inventories: If you have a large and complex inventory of parts, components, or products, an intelligent numbering scheme can help you keep track of everything more efficiently. You can quickly identify and locate the items you need using a structured system of codes and symbols.
  • Streamlined procurement: Using an intelligent part numbering scheme, you can streamline your procurement processes and reduce the risk of errors or delays. A clear and consistent system for identifying parts ensures that you order the right items.
  • Standardization: If you work in a highly regulated industry with strict quality standards, an intelligent numbering scheme can help you ensure compliance. A consistent system of codes and symbols helps ensure that your products meet the required specifications and are safe for use.

Non-intelligent part numbering schemes

A non-intelligent numbering scheme defines part numbers simply. Five or 10-digit numeric values are usually assigned for each new part and sequentially incremented. The numbering is consistent for each new part as it’s added to your company’s part library — regardless of what the part is or does.

A non-intelligent numbering scheme is different from an intelligent part numbering scheme in that it does not provide any information about the part, category, or function. You might find it challenging to identify parts later.

Pros of a non-intelligent numbering scheme

  • Simple and fast implementation: Non-intelligent numbering schemes are straightforward and require no thought process when assigning new values. This simplicity results in rapid implementation times.
  • Limitless expandability: Non-intelligent numbering schemes are infinitely expandable as the product evolves and new parts and part categories are added to the library. It’s easy to add new parts to the product.
  • Consistency and continuity: With non-intelligent part numbers, it is easy to maintain continuity and consistency in numbering since there is no need to worry about the part type, function, or other characteristics.

Cons of a non-intelligent part numbering scheme

While a non-intelligent part numbering scheme does have its pros related to speed and expandability, there are some drawbacks to implementing a non-intelligent scheme:

  • Difficult to “read”: Due to the lack of embedded information, non-intelligent part numbers are hard to interpret. It can be challenging to know the part without cross-referencing some other piece of information. This additional work can lead to delays and mistakes.
  • Lack of information: Non-intelligent part numbers do not provide information about the part type, function, or any other characteristics. This lack of information can be problematic, especially when dealing with complex systems that require a lot of cross-referencing.
  • Potential for duplication: Since non-intelligent part numbers are assigned sequentially and are composed of fewer unique elements, duplication or reuse is a risk. An automatic, software-based system (e.g., PLM tool) will be helpful to prevent part number duplication and reuse.

When to use a non-intelligent part numbering scheme

A non-intelligent numbering scheme is suitable for vertically oriented businesses that manufacture products with many parts and where there is less risk of misinterpretations due to limited reliance on external partners.

The following are some situations in which a non-intelligent scheme may be appropriate.

  • Low complexity: If the parts you produce are not very complex and do not require detailed specifications or instructions, a non-intelligent scheme may be sufficient. For example, if you are utilizing standard electronic components like resistors or capacitors, a non-intelligent numbering scheme may work well.
  • Cost savings: Non-intelligent schemes are typically easier to implement and maintain. They also require less management, training and resources. Therefore, a non-intelligent scheme may be a good option if your business is looking to save costs.
  • Standardization already in place: A non-intelligent scheme may be appropriate if you work with parts with well-defined characteristics and do not require additional information in the part number. Standardized parts are usually easy to identify and do not require complex part numbering schemes.

Duro’s recommendation: A semi-intelligent part numbering scheme

At Duro we see a wide array of part numbering schemes being utilized across our customer base. While we offer an out-of-the-box part numbering system based on a set scheme, Duro’s PLM supports a variety of different customer part numbering schemes — ranging from intelligent to non-intelligent and in between.

From our perspective, no matter the scheme, the most important concept to keep in mind when designing your scheme is that:

There must not be any room for subjectivity or interpretation. The rules for assigning a part number to a new part must be clear and concise.

While Duro recognizes the utility of both the intelligent and non-intelligent part numbering schemes, Duro recommends a hybrid of the two — where there is a short (3- or 4-digit) prefix code which defines the part category, with a longer (5- to 7-digit) counter suffix that is incremented with each new instance of the category.

This is often referred to as a “semi-intelligent” part numbering scheme. This makes it easy to add new prefixes as new categories are added to your product in the future, but the granularity is coarse enough that it’s fast and simple to assign new part number values when new parts are added to your library.

The part numbering scheme we offer in our out-of-the-box system is a <3> – <5> format, with a 3-digit numeric category prefix, a 5-digit numeric suffix counter, and a hyphen between the two to create an easy visual separation to enhance readability. This allows for 999 unique categories and 99,999 unique parts per category. We challenge any team to run out of unique part numbers using this scheme!

How to define categories in the part number

When selecting your list of categories, the only decision to make is how coarse or fine you want to make them. For example, you could simply have only two categories:

  • Purchased
  • Custom

For some teams this works just fine. Or you can go the other extreme and list out every possible category imaginable:

  • Resistor
  • Diode
  • LED
  • Capacitor
  • Screw
  • Bolt
  • Nut
  • Washer etc.

 The only important thing is to make sure there’s no room for interpretation. That means it’s clear to everyone which category they should pick. Confusion can happen when category lists include a mix of some generic (coarse) terms and some specific (fine) ones.

How to handle variants in your part numbering scheme

Some teams use a third field in their part number scheme to define variants of a part or assembly. It’s often represented as a 2- or 3-digit suffix, which defaults to 00 for the first instance of a part.

When a “variant” of a part is added to the library, the base part number value is kept the same, but the variant field is incremented. It’s used to show there is some form of relationship between two parts, but not enough for them to be considered exactly the same.

However, we don’t think this is the best avenue because it leaves room for interpretation. Two people may reasonably disagree on whether two parts are completely unique or just variants of each other. This can happen when the rules for what constitutes a variant aren’t clear.

Parts are defined by their parametrics. Anytime two parts have different parametrics, they are not considered the same (in a strict literal sense). But, all parametrics are not assigned equal priority by all people. So, engineers will result in subjectively selecting which parametrics constitute two parts being different and which are considered equivalent.

When you have a “variants” field in your part number scheme, it exacerbates the problem by empowering someone to make a subjective decision on the matter. This ultimately leads to inconsistencies in your parts library. Anyone not involved with these decisions (i.e. a third-party contract manufacturer or supplier) may get confused by the inconsistencies and make a costly mistake in production.

Recommendation: Don’t add a variant suffix or group like parts into variants. It’s more important to avoid mistakes in production.

Helpful tips and tricks for part numbering schemes

Several tips and tricks can help ensure its effectiveness and ease of use when creating a part numbering system. Below are some of the most helpful and vital things to consider:


  • Do keep it simple and consistent.
  • Do use consistent fixed length numeric CPN schemes
  • Do utilize a part categorization system to group similar parts.
  • Do consider using a prefix to denote the part category.
  • Do avoid special characters or delimiters that can cause data entry and retrieval issues.
  • Do keep the length of the part number manageable.
  • Do incorporate a sequential numbering system to facilitate easy tracking and organization.


  • Don’t use alphabetic characters
  • Don’t use a mix of coarse and fine granularity in your category list
  • Don’t use variant suffixes
  • Don’t use leading zeros

We elaborate more on our post regarding the best practices when utilizing part numbering systems of any scheme.

Part numbering schemes with Duro

At Duro, we understand the importance of a practical part numbering system. Our team of experts can help you design a part numbering scheme tailored to your unique needs, whether you require a simple sequential numbering system or a more complex and structured part number system. 

By leveraging our state-of-the-art PLM system, we can help you streamline your BOM management process, remove the chance of part duplication, and improve efficiency across your business operations.

Ready to streamline your part data management processes? Contact Duro today to request a demo and see how our cloud-native PLM can help your team improve efficiency and productivity.

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