BOMs are an essential information tool in manufacturing companies and link all the departments involved in the product engineering process (PEP). Each design domain generates a discipline-specific variant of the engineering bill of materials (EBOM) with its parts and assemblies. Along the entire value chain, these “as-designed” BOMs provide information on product’s type, form and its concept to all specialist departments involved in the manufacture and subsequent maintenance of the product. They help the engineering teams coordinate with each other and involve colleagues in manufacturing, procurement and logistics, in production, assembly and quality assurance, right through to documentation and after-sales service.
On the one hand, the header data of the BOM contains general project information such as the customer, product and its quantity, author of the BOM, version and much more. On the other hand, the individual items listed contain the technical characteristics of the components and their planned quantity alongside the manufacturer information.
The departments downstream of the design engineering department have a different view of the BOM and process it differently, depending on the tasks for which they are responsible.
Mechanical design engineers work differently from their colleagues in electronics, electrical engineering and fluid dynamics. In mechanical engineering, the form of the product and its detailed structure is relevant, which is why mechanical design engineers generate a structured, multi-level BOM from their CAD drawings. Its data reveals the exact location of individual parts, assemblies and subassemblies in the hierarchical product structure.
For the electrical engineering disciplines, material management prefers to work with single-level or flattened BOMs, which aggregate the total number of planned components with the same attributes. Colleagues in cable assembly or working on the control cabinet are more likely to be helped by single-item BOMs to supplement the wiring schematics and the terminal strip structure, or to supplement layout and assembly diagrams in PCB manufacturing.
In order to comply with statutory documentation obligations, all engineering disciplines must include an “as-built” BOM with the documentation. This contains all item identification information such as the manufacturer, EAN number, designation, etc.
Industrial customers find a BOM of spare and wear parts helpful to allow parts either to be stocked or to be ordered on time.
Once product planning has reached a certain level of maturity, the work preparation department receives the plans and BOMs. They convert the EBOM into a manufacturing bill of materials (MBOM) by adding information for procurement, manufacturing, assembly, quality assurance and shipping to the design BOM.
The work preparation department creates the work schedule, which, together with the MBOM, forms the basis for the internal production orders. All information relevant to production is derived from this. Ideally, it defines the start of manufacturing engineering. In the event of outsourcing, the manufacturing partner receives the complete documentation including the EBOM.
The earlier manufacturing is involved in the design process, the easier it is to guarantee problem-free production. Depending on the extent of digitalization in the manufacturing company, the design data can be linked to digital assembly instructions and test forms that can be retrieved when needed.
As a rule, item master data is synchronized between the ERP and CAD systems via the item number. When the BOM is entered in the ERP system or transferred electronically, the items on the BOM are automatically compared with the ERP item master data. This means that the necessary procurement information about suppliers, order numbers, prices, etc. is all available to the purchasing department. Purchased parts that have not yet been created in the item master data are flagged, as are those where the customer specifies a particular manufacturer.
Now the purchaser decides whether to buy the required material or to provide it from existing stock. Flattened BOMs help purchasers when matching to packaging units, or conducting price negotiations and so on. If components with long delivery times are required, they can be ordered early. If items in the BOM are flagged as customer-supplied parts, the purchaser monitors whether the customer meets the agreed delivery date.
If the BOM contains an item for which there is a significantly cheaper variant of similar design available, the purchaser assesses the necessary design change with the design engineers. The adapted design changes the EBOM, which in turn feeds the new information into the MBOM.
If a manufacturer withdraws an item, the purchasing department changes the status of the item accordingly. The next time the item master data is synchronized between the ERP and the CAD system, this information automatically becomes available in the design. The design engineers can now only select this item up to a particular date or not at all.
If a complex heavy goods transport operation is to be scheduled, this can also be organized in good time with the help of the MBOM. Shipping is a costly operation for many industrial products and medical devices. Correctly dimensioned transport crates for machines or diagnostic imaging equipment, for example, have to be planned, designed and built in good time.
As with direct CAD-ERP integration, users of a PLM system benefit from the intelligence of the XPLM CAD connectors. They generate the BOMs for each development domain exactly as specified. The process is triggered automatically by an event such as saving a potentially final version. At the same time, the connectors trigger rule-compliant conversion into neutral formats, which they make available electronically at the defined storage location. This in turn can trigger a notification to other specialist departments or to suppliers.
For this purpose, PLM users define the structures of the BOM and whether they contain variants or not. Such variants can be used to associate individual components with specific factories because they prefer to use local materials or follow country-specific compliance requirements.
In a multi-CAD PLM system, the BOMs from different domains are linked logically. Even if the various domains save their versions at different intervals, the PLM system transparently shows which valid versions are compatible at all times.
If a product is changed, the connectors identify the differences. The comparison BOMs automatically show the additional material or the superfluous material already ordered, thus significantly reducing the effort required in purchasing. This is especially true for the extensive BOMs that often accompany E/E engineering. If a product such as a machine is extended, the difference BOMs first and foremost prevent all the material for the product being ordered again.