Precise Bill of Materials don't Exist!
Martijn Dullaart
Shaping the future of CM | Book: The Essential Guide to Part Re-Identification: Unleash the Power of Interchangeability & Traceability
There is no such thing as precise bill of materials, they do not exist! So there I said it...
Well this does require a little bit of explanation and nuance. In one of my previous articles I wrote about?Parts don't have Revisions, where I explained the different data models in PLM, ERP and?CM2. Here is a quick refresher of the different setups (for more details check the?article):
All above models are known as Imprecise Bill of Materials and I on purpose did not include a Precise Bill of Material concept to not overcomplicate the article. However in the mean time I have been involved in various discussions on the topic of Precise vs Imprecise BoMs. So what is the difference??
Imprecise vs Precise Bill of Materials
Imprecise BoMs are bill of materials where child parts are linked by Part Number
That essentially means that it does not matter which revision of the child part is used. However revisions rules can be applied to identify the valid or preferred revision at a specific moment in time e.g. Latest Released. If you do care about which revision is used, you should have re-identified the part (which you can read all about in my book:?The Essential Guide to Part Re-Identification).
Precise BoMs are bill of materials where child parts are linked by Part Revision.?
That means the Parent Part Revision links to the Child Part Revision, and in doing so creating a very precise relation. Every change means you revise all the way up to the final product. Changing the toilet seat on a submarine, would require you to revise all parent parts up to the submarine itself. As pictures speak louder than words, see below the difference between Imprecise and Precise Bill of Materials.
While you could technically switch from Imprecise to Precise BoMs during the part's lifecycle, that requires a very mature organization and good understanding of the logic involved. If Imprecise BoMs are applied throughout the part's lifecycle, you will face challenges in the procurement, production and maintenance phases. With Precise BoMs the standard rule, that Parts/Materials or put on stock based on their Part/Material Number, not based on their revision, is violated. You will have to put revisions of parts on stock, so basically the revision becomes part of the Part Number. Every change forces you to issue a new Part Number from the perspective of the operational world (Procurement, Production, and Maintenance).
That is also why you often see that a need arises to do small changes that are captured in some form of iteration or version to prevent from having to revise till the product level. Which will result in making the Precise Bom into an Imprecise BoM. Hence the title of this article: Precise Bill of Materials don't exist!
Conclusion
If it comes down to a choice, I think in most cases, the Imprecise Bill of Material is highly preferred as it supports all downstream processes. And within this concept I would still recommend a combination of the Common ERP solution and CM2 Solution as a foundation, as I earlier explained in?Parts Don't Have Revisions.?
I have yet to see a Precise BoM implementation where the benefits outweigh their disadvantages (so feel free to surprise me). Often Precise BoM implementations are part of legacy implementations and this history is still being dragged along. It is better to invest in a good implementation of Imprecise Bill of Materials with concepts like Manufacturer/Vendor Parts Lists and a good?to help guide part re-Identifications, than to create overly complicated solutions to make a Precise BoM work.
Header Photo created by Martijn Dullaart based on a template from Creative Chaos 77 on Canva
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Helping manufacturing companies with digitalization
3 个月Thanks for your statement Martijn, it could be just the push that will help hesitant people make the right choice??
Bespoke Generative AI for Engineering & Manufacturing (PLM, MES, ERP) | Cloud Native | Air Gapped | System Integration | Concepts, Technologies, Execution
3 个月Sara O'Neil-Manion FYI.
PLM Solution Arhitect
3 个月Hello Martijn Dullaart Out of experience, precise BOM's are creating a high level of complexity, as a big con, it creates a high demand of material numbers in the erp system, especialy if your material no is equal to your item id+rev id There has to be a clear diferentiation between material no and item id+rev id one of the down sizes is also the fact that any change in the BOM will affect the Routing, all will result in hard mentainance and low data quality. Impricise way is better but you have to be specific in the MBOM (100%) structures accordin to variants and plant related features Thank you
Berater bei der Firma CPS GmbH
3 个月Hi Martijn, nice to see there is someone else dealing with this topic. The #TPLE concept is exactly what you call PreciseBillofMaterials. But not only for Hardware, Software is included too. And it extends the BOM with a complete functional net. Please contact Chris Seiler for further information.
Bespoke Generative AI for Engineering & Manufacturing (PLM, MES, ERP) | Cloud Native | Air Gapped | System Integration | Concepts, Technologies, Execution
3 个月Imprecise BOM for all post engineering operations - OK. But certifications, for example FAA, do requires precise. I liked the article a lot. Yet it seems to propose all or nothing? That is not necessarily "what the world needs." Yes it is complex, that is what separates elegant solutions from workable solutions. Same with no revisions.?Yes, that’s a good rule, but there are exceptions, especially in make to order -?the more complex and custom the more you revise.