This time a few theoretical posts about BOM handling, how the BOM is used in different processes as Engineering To Order (ETO), Make To Order (MTO) and Build To Order (BTO) organizations and finally which PLM functions you would expect to support these best practices.
I noticed from various lectures I gave, from the search hits to my blog and from discussions in forums that there is a need for this theoretical base. I will try to stay away from too many academic terminologies, so let’s call it BOM for Dummies.
Note: All information is highly generalized to keep is simple. I am sure in most of the companies where the described processes take place more complexity exists.
What is a BOM?
A BOM, abbreviation for Bill of Materials, is a structured, often multi-level list of entities and sub-entities used to define a product
I keep the terminology vague as it all depends to who is your audience. In general when you speak with people in a company that does engineering and manufacturing, you have two major groups:
- The majority will talk about the manufacturing BOM (mBOM), which is a structure that contains the materials needed to manufacture a product in a certain order.
We will go more in depth into the mBOM later.
- When you speak with the designers in a company they will talk about the eBOM, which is a structure that contains the components needed to define a product.
Both audiences will talk about ‘the BOM’ and ‘parts’ in the BOM, without specifying the context (engineering or manufacturing). So it is up to you to understand their context.
Beside these two major types of BOMs you will find some other types, like Conceptual BOM, Customer Specific BOM, Service BOM, Purchase BOM, Shipping BOM.
Each BOM is representing the same product only from a different usage point of view
The BOM in an Engineering To Order company
In an Engineering to Order company, a product is going to be developed based on requirements and specifications. These requirements lead to functions and systems to be implemented. For complex products companies are using systems engineering as a discipline, which is a very structured approach that guarantees the system you develop is matching all requirements and these requirements have been validated.
In less complex and less automated environments, you will see that the systems engineering is done in the head of the experienced engineers. Based on the requirements, they recognize solutions that have been done before and they build a first conceptual structure to describe the product. This is a conceptual BOM, often only a few levels deep, and this BOM is mainly used for costing and planning the work to be done.
A conceptual BOM could like this (open the picture in a separate window to see the animation)
Depending of the type of engineering company, they are looking for the reuse of functions or systems. The reuse of functions means that you manage your company’s Intellectual Property (IP) where the reuse of systems can be considered as the reuse of standard building blocks (modules) to build a product. The advantage of system reuse of course is the lower risk, as the system has been designed and built and tested before.
From the conceptual BOM different disciplines start to work and design the systems and their interfaces. This structure could be named the eBOM as it represents the engineering point of view from the product. In Engineering to Order companies there is a big variation on how to follow up after engineering. Some companies only specify how the product should be made, which materials to use and how to assemble them. The real manufacturing of the product is in that case done somewhere else, for example at the customer site. Other companies still do the full process from engineering and manufacturing.
As there is usually no reuse of the designed products, there is also no investment in standardizing items and optimizing the manufacturing of the product. The eBOM is entered in the ERP system and there further processed to manufacture the product. A best practice in this type of environments is the approach that the eBOM is not a 100 % pure the eBOM, also items and steps needed for manufacturing might be added by the engineers as it is their responsibility to specify everything for manufacturing without actually making the product.
This animation shows on high level the process that I described (open the link in a separate window to see the animation)
What PLM functions are required to support Engineering To Order
The following core functions apply to this process:
- Project management – the ability to handle data in the context of project. Depending on the type of industry extended with advanced security rules for project access
- Document management – where possible integrated with the authoring applications to avoid data be managed outside the PLM system and double data entry
- Classification of functions and/or systems in order to have an overview of existing IP (what have we done) and to promote reuse of it
- Item management – to support the eBOM and its related documentation. Also the items go through a lifecycle representing its maturity:
– The eBOM might be derived from the mechanical 3D CAD structure and further extended from there.
– For design reviews it would be useful to have the capability to create baselines of the eBOM including its specifying documents and have the option to compare baselines to analyze progress
– The completed eBOM would be transferred to the ERP system(s). In case of a loose ERP connection a generic XML export would be useful (or export to Excel as most companies do)
- Workflow processes – to guarantee a repeatable, measurable throughput of information – both approval and change processes
- Supplier Exchange data management – as many ETO companies work with partners and suppliers
- Issues Management – handling issues in the context of PLM gives a much better environment for a learning organization
- Requirements Management – specially for complex products, tracking of individual requirements and their implementation, can save time and costs during delivery
- A configurator allowing the sales engineering people to quickly build the first conceptual BOM based on know modules combined with engineering estimates. This is the base for a better controlled bidding / costing
Let me know if this kind of posts make sense for you …..
Next time we will look at the BOM in a Build To Order process