How you can define alternate and substitute items in openBoM
Question about alternate and substitute items often come up from our users. On this post I want to share some of the answers we provide and current practices. Let’s start with some background and definitions.
The idea of both alternate and substitute items is relatively simple: it’s about the need to replace one BOM item with another. At a fundamental level, it is about managing the interchangeability of Items in your system.
A part is interchangeable with another part if the relevant functional and physical characteristics (i.e., properties) are similar and can be used instead of the original part without any specific procedural and functional changes. A Commonly used similarity definition includes “3Fs” (form, fit, and function). Form generally speak to sizes, fit usually speaks to fitting and mating with other parts, and function is the ability to perform with the same physical characteristics. So, from a practical standpoint, if you can exchange one part with another in product inventory, you can consider parts interchangeable.
Based on the definition of interchangeability, each item can have an approved list of items that can replace it, i.e., an alternate item. There are multiple reasons why a standard item might be replaced, e.g., stock shortages, lead times, availability, cost, etc. Engineering items are not often replaced, but can still be provided by multiple partners. That happens in rare use cases, in my experience.
So, what is the difference between an alternate and substitute item? In my experience, the most commonly recognized differentiation is scope of replacement. While alternate is usually considered as “global” product replacement, substitute is a replacement that’s done within the scope of a specific BOM (product). These definitions come from the practice of BOM management in ERP, and sometimes, in PLM systems.
With the flexible practice of BOM management provided by openBoM, alternate and substitute items can be applied without the need for rigid formalized procedures. For individual users, the scope of a “product” is largely not specified and usually is about the management of different types of BOMs. We are considering to bring a “scope” of product to openBoM as a context for a specific TLA (top level BOM assembly) or perhaps, define it as a full scope of all BOMs managed by the Team subscription (within the scope of Team Administrator).
So, how can you define alternate items? The easiest way to do so is to define a “sub-level” BOM for an item you want to define as a replacement. The list of items in this sub-level will represent a list of all alternate options. You customize the list and use one of the properties to identify what is a “currently” used item among all alternate options.
A “substitute item” is considered as the easiest option to manage a substitute by specifying it in a separate list property defined for such a purpose in a BOM. Although, you may consider this option as “quick and dirty,” it is an efficient way to bring immediate information about BOM item substitutes. And it’s easily realized thanks to the flexibility of the openBoM data modeling paradigm.
Conclusion. We invite you to think along with us and share your practices and needs for the management of alternate and substitute items. With future improvements coming with multi-level BOM management, part catalog, and production planning in openBoM, we will work to clarify and improve the way both alternate and substitute BOM items can be managed. Contact me at oleg @ openbom. com. I’d love to get in touch and discuss how both alternate and substitute items can be managed today and how we can improve it in coming releases.
PS. We should know each other better. If you live in a Greater Boston, please let’s have a meeting (coffee is on me). If you’re located in other places, let’s have a virtual coffee session — I will figure out how to send you a real coffee for our virtual coffee session.