Single Bill of Material – Holy Grail or Pipe Dream?


What I learned this week … is a thought sparked by a post in the Daily PLM Think Tank on Engineering and Manufacturing Data Management back in 1992. The post isn’t from 1992, but Oleg was re-reading some books from that time and commented on some issues that the manufacturing industry is still struggling with after 17 years of progress. Single BOM GrailI know there are strong proponents of the single bill of material (BOM) concept, but I wonder if we will every really get there and whether we haven’t made some really good progress managing bills of material with different perspectives. And maybe, just maybe, there is an easier way.

The Single Bill

Oleg’s post doesn’t go into detail, but the first issue he shares is “Multiple Bills of Material” and follows with “Relations between Design, Engineering BOM and Routing.” The truth is that Engineering works from a different BOM than Manufacturing does. And, as the post also points out there are also separate “Maintenance and Repair Bill of Materials.” There are strong arguments for a single BOM that supports different views for different people (engineers vs. manufacturing vs. service, etc.). And there are very strong proponents (to the tune of religious zealot levels of belief). So for this discussion, let’s take as a given that it would be great to have a single BOM.

Single BOM – Feasible or Folly?

Now that we are all friends, it is time to ask a practical set of questions:

  • Is a single BOM really feasible?
  • How hard of a transition would it be to support processes for a single BOM?
  • And (most importantly) how much is it worth?

Let’s face it. Engineers care about things that manufacturers don’t. And manufacturing engineers care about things that design engineers don’t. Manufacturing really requires a lot more information than engineering, they require an integrated view of both the materials and procedures required to product a product – a Bill of Process (BOP). See more thoughts on the BOP in Research Rap: Enhancing Productivity and Reducing Cost with MPM and the Digital Factory and the related research report. Can the BOP be a different view of the same BOM? Yes, potentially. But that asks a lot of the people, the process, and the data model.

One other consideration is the difference between what an ERP needs to execute the business of manufacturing as compared to what engineers need. ERP BOMs frequently include information used for costing and consumable items used in manufacturing. They also summarize a detailed set of components into a single part number for procured items or sub-assemblies based on how they are physically present in the manufacturing environment. Even ERP routings are much simpler than the detailed BOP, primarily focusing on the level of detail required to track cost and plan production. See Research Rap: Complementary Roles of ERP and PLM in Innovation and look for some new Tech-Clarity research coming soon on the integrated roles of ERP and PLM. Again, can these be different views of the same data? Of course. But as we have proven by history, people aren’t moving in that direction with any great haste because it is simply hard to pull off.

We haven’t even touched on service, spare parts, preventitive maintenance, or discussed tracking “as built” or “as serviced” BOMs. But let’s just agree for the sake of argument that they are not easy to integrate.

Cost-Benefit of the Single BOM

OK, you are probably thinking “why didn’t he answer the questions he asked in the beginning of this section? All we have discussed so far is that it is difficult. So let’s conclude that there is a cost associated with moving to a single BOM approach. And for now, let’s ignore what it would take to transition from the “as is” to the “to be” state.

Now that we have agreed there is challenge and cost associated with a single BOM approach, the most logical question is to ask how much value the single BOM provides. Clearly, a single BOM would contribute to fewer errors and disconnects between all of the different people in involved in a product over the product lifecycle. It would go a long way towards the “single version of the truth” in regards to products that we all profess. But here is where I want to throw out a different question. Instead of comparing the cost-benefit of the single BOM approach, let’s look back at history and see if an alternate approach has been evolving as PLM has matured.

Single BOM or Associated BOMs?

Manufacturers and PLM providers have not ignored this topic. I would argue that a lot of progress has been made. How? Companies have spent a lot of time and effort making logical connections between different BOMs, and developing tools to help develop and synchronize different BOMs. For example, PLM, MPM, and Digital Manufacturing software helps companies translate an engineering BOM into a manufacturing BOM and then further into a BOP. In fact, they have gone further upstream to match conceptual BOMs and requirement structures downstream to BOMs. Maybe you would call these “workarounds” to the real answer of a single BOM. But I would propose a different view based on history and my observations. Perhaps engineers have done what we do best – addressed the problem in the most practical way as opposed to the most elegant way to solve a problem.

So those are my thoughts, I hope you found them interesting. I will admit that I am not a zealot in one direction or the other, and recognize those that are passionate about a single BOM. I am happy to be educated on different views, but I think the question needs to be asked. Are we trying to achieve our goals by taking the long, hard road when an easier path might suffice? Or am I all wet?