One common practice among manufacturers is using bills of materials (BOMs) to guide the manufacturing process. Even before the advent of CAD, manufacturers – or, more accurately, their designers and engineers – created all the designs that defined their products. They would then use these designs to create a list of what they’d need to buy or build to manufacture the product. It is this list that is known as the bill of materials or BOM.
Today, designers and engineers still create bills of materials, but now they do it using CAD software. Given the importance of BOMs in manufacturing, learning their intricacies is essential. This article, therefore, details the role of BOMs in manufacturing and design, their uses, how to create BOMs in leading CAD software, how to prepare your CAD model for BOM generation, and how to customize and export BOMs. Let’s get started.
Table of Contents
Understanding the Role of a BOM in Design and Manufacturing
Bills of materials have long been essential in manufacturing. Today, as has always been the case for years, BOMs provide a comprehensive list of what the manufacturer needs to build a product, i.e., a manufacturing-ready parts list. They typically specify the name, quantity, description, material, and, in some cases, the suppliers of each component that makes up the product.
In this regard, they serve as the single source of truth for purchasing materials and components and manufacturing products. Their utility extends beyond manufacturing because service departments use them to identify components that need replacing.
But as manufacturing has evolved, new technologies have emerged that serve as sources of truth, too. Such technologies include the digital thread and the model-based enterprise. NDespite these new technologies, BOMs remain a vital part of design and manufacturing. And this is best exemplified by a number of recent developments.
Autodesk in early 2024 introduced a feature that allows you to generate a bill of materials from CAD files using Fusion. Fusion’s introduction of BOM capabilities hinged on the uses of BOMs, which we have discussed in detail below. Autodesk in fact underscored the role of BOMs as a means of sharing product information between upstream and downstream teams.
Secondly, SolidWorks and its parent company, Dassault Systèmes, are championing a new virtual product modeling approach that helps teams design, document, and communicate product details. This approach integrates BOM management into a single digital environment that’s accessible to all members. Simply put, it’s meant to enhance BOMs, not replace them.
Types of Bills of Materials
Within the domain of design and manufacturing, there are three main types of bills of materials:
- Engineering bill of materials (EBOM): An engineer typically creates an engineering bill of materials from CAD files during the design stage. This means the EBOM is linked to the CAD files that capture design data like geometry and dimensions. The EBOM provides a comprehensive list of all the parts, items, subassemblies, and assemblies that make up a product.
- Manufacturing bill of materials (MBOM): The MBOM lists all the parts and assemblies required to manufacture a finished product. This bill of materials captures all the parts that need to be processed prior to being added to the assembly.
- Service bill of materials (SBOM): The SBOM lists all the serviceable parts and components.
Uses of a Bill of Materials
1. Provide Product Information
A BOM captures all the essential information on how to manufacture a product. It provides details such as the type of materials and the quantity. It also shows which parts are sourced from suppliers and which are made in-house.
2. Facilitate Change Control
When engineers and designers introduce a potential engineering change in a product, they can use the BOM to identify the components that this change will affect. This helps them calculate the cost of the engineering change.
3. Support Product Simplification or Standardization
A BOM that captures graphical elements can help engineers identify elements that can be simplified or standardized. For instance, components that are unique to only one parent influence the cost of maintenance; often, this cost is higher than the benefits offered. The best recourse in such an instance is to substitute this component with a more standard one or to simplify the design in order to eliminate the component.
4. Enable Part Serviceability
As stated earlier, an SBOM provides a comprehensive inventory of all serviceable parts. It’s worth mentioning, however, that a manufacturer’s service department can still use the general BOM to identify the exact components they need whenever a product breaks down. It outlines the components and their quantities, allowing the sales department to ship the correct parts or components.
5. Warranty Control
Manufacturers often revise the BOM to capture product changes. They also keep a record of the revisions. The revisions come in handy when companies need to confirm whether the product’s warranty is voided. They can simply refer to all the records of the BOM to determine the time it was built and whether the user added components that can void the warranty.
6. Costing
Manufacturers can use the information captured in the BOM to calculate the cost of the product. They can rely on details such as the quantities and materials of each component to arrive at the final figure.
7. Planning and Scheduling
A comprehensive BOM details the order in which the components are needed during manufacturing. When fed into the product lifecycle management (PLM) systems, this information can help the procurement team to order the components and have them delivered as and when they are needed.
8. Assess Component Shortages
Manufacturing isn’t always smooth sailing; issues can occasionally crop up. One of these issues can be a shortage of individual components needed to manufacture a part. This issue can arise from supplier-specific issues or machine breakdowns, perhaps due to failure to conduct maintenance. In such a case, the manufacturers can use the BOM to assess the exact quantity of components that are short.
9. Evaluate Consumption
Large-scale manufacturing naturally involves high volumes of parts and components. It can, therefore, be challenging to determine the components already consumed. That’s why manufacturers often use backflushing. It entails specifying checkpoints, with the technicians then using the BOM to identify the components that should have already been used whenever the product (in its current state) passes the checkpoint.
Creating a BOM in Popular CAD Software
AutoCAD
AutoCAD does not automatically let you create a bill of materials from CAD files. And neither does AutoCAD LT. Instead, you have to use an industry-specific AutoCAD Toolset like AutoCAD Architecture, Electrical, MEP, Plant 3D, or Mechanical. (Your AutoCAD subscription includes these toolsets.) And the procedure is slightly different for some of these toolsets.
AutoCAD MEP
To create a BOM in AutoCAD MEP, follow these steps:
- In the Style Manager, create a Property Set Definition for an object type or system whose BOM you want to create.
- Apply or attach this Property Set Definition to all objects associated with the object type in Step 1. To do this:
- Select all the objects
- Click the Properties palette, select the Extended Data tab, and click the Add Property Sets icon
- Add all the needed Property Sets.
- Create a schedule style for the object type and ensure the property set information is shown in its columns.
- Use the SCHEDULEADD command to add a schedule in the drawing.
- From the Properties palette, select the schedule style that corresponds to those objects.
- Select all the needed objects when prompted and finish the schedule insertion.
These steps create a Schedule table, which serves as a BOM table.
AutoCAD Mechanical
AutoCAD Mechanical supports three procedures for creating a BOM, as detailed below. The first procedure entails creating a BOM for the entire drawing in AutoCAD Mechanical; here are the steps you should follow:
- Click the Annotate tab
- On the BOM ribbon panel, click the BOM button
- Enter the letter M at the command prompt.
Here are the steps to follow when creating a BOM for an assembly in AutoCAD Mechanical:
- Switch on the mechanical browsers using the AMBROWSER command. AutoCAD Mechanical Toolset has a mechanical browser that shows how parts and assembly are organized hierarchically in a mechanical structure. Only use this command if the software hasn’t automatically displayed the browser.
- In the browser, right-click the assembly whose BOM you want the software to create.
- Select the Create Assembly BOM option from the menu that pops up.
- AutoCAD will automatically create the BOM and show it in its BOM dialog box.
Lastly, AutoCAD Mechanical lets you create a BOM for a drawing border in model space. But keep in mind that only borders created using the AMTITLE command support this functionality. Here are the steps you should follow:
- Click the Annotate tab
- On the BOM ribbon panel, click the BOM button
- Within the model space, click the border for the drawing whose BOM you want AutoCAD to create
- AutoCAD will automatically create the BOM
SolidWorks
SolidWorks lets you create a bill of materials from CAD files. Specifically, you can create BOMs directly from parts or assembly without creating a drawing first. Here are the steps to follow:
- Ensure the part or assembly is open
- Next, select Insert, choose Tables, and finally click Bill of Materials.
- Use the Bill of Materials Property Manager to define settings like the BOM type, such as a parts-only or top-level BOM.
- Place the BOM in your drawing by clicking the graphics area.
Inventor
Autodesk Inventor lets you create a BOM table that contains information about all the components in an assembly. To create a BOM in Inventor, follow this procedure:
- Click on the Assembly tab.
- In the Manage ribbon tab, click the Bill of Materials button, which opens the Bill of Materials dialog box that also contains the BOM table.
- The BOM dialog box lets you customize the BOM table as well as export or import data.
Fusion
Fusion uses a cloud-based approach to BOMs. This makes it easy for users to collaborate and share product data between designers and manufacturers. Here are the steps you can follow in order to create a bill of materials from CAD files in Fusion:
- In the Solid tab, click the drop-down arrow under the Assemble ribbon tab.
- Select Bill of Materials from the drop-down menu, which automatically creates a BOM that can be shared or updated. In fact, Fusion saves the BOM changes along with your design, enabling you to access even the older versions of the bill of materials.
Menu to Create Bill of Materials from CAD Files in Fusion
Fusion also lets you access the BOM feature from other tabs in the design workspace.
Creo
You can create a bill of materials from CAD files containing parts and assemblies in Creo Parametric. In fact, you can create a sub-assembly BOM. The software also allows you to customize the text output format for a specific form of content or presentation or create the BOM in table format in drawings. But foundationally, creating a BOM in Creo Parametric involves the following steps:
- Click the Tools tab and select Bill of Materials, which opens the BOM dialog box
- Select either Top Level or Subassembly under Select Model.
- If you select the Subassembly option, Creo lets you select the particular subassembly for which you want to create a BOM. It does this using the SELECT menu.
- Indicate whether you want objects like Skeletons, Unplaced, and Designated by checking their respective boxes under the Include section
- Finally, click OK.
BricsCAD
BricsCAD represents the BOM as a table entity that you can place anywhere in the CAD drawing. To create a bill of materials in BricsCAD, follow these steps:
- Type BMBOM to insert a BOM table in your current drawing.
- Use the BMBOMPALENOPEN and BMBOMPANELCLOSE commands to open and close the BOM manager panel, respectively.
Preparing Your CAD Model for BOM Generation
Most CAD software programs automatically generate the bill of materials from CAD files with minimal input from you, the user. The generated BOM captures all parts, part references, and assemblies. It also includes part numbers, which the software often sets automatically.
However, software like Inventor lets you include custom properties in the BOM. So, ensure you have defined such properties before creating the bill of materials from CAD files in Inventor.
Generally, you do not need to do much to prepare your CAD model for BOM generation. The software handles everything automatically, provided you’ve already created your 3D model.
Customizing and Exporting Your BOM
Customizing Your BOM
Many leading CAD software lets you customize your BOM table. For instance, Inventor allows you to change the properties of the BOM table. You can add more properties (i.e., add more columns and fields), renumber items, change display order, and remove columns and properties.
Creo lets you specify the output format. You can choose the default BOM HTML output format, which includes hyperlinks to parts in the assembly. These hyperlinks allow you to open or see additional information about the associated parts. Alternatively, you can choose the BOM text output format, which, as the name suggests, uses a text-based format to list the quantity, type, and name of each part in the assembly.
For its part, SolidWorks has a property manager for BOMs. This property manager lets you control the BOM type, the size of the BOM table, how the software handles missing/replaced components, item numbers, borders, and text formats. The property manager also supports layer management.
Exporting BOMs
SolidWorks lets you export your BOM in various formats, from .txt, .xlsx/.xls, .csv, and .pdf to .dwg, .dxf, .edrw, and .sldbomtbt. You can also print the BOM. Fusion also lets you export BOMs, enabling you to download it as a file on your computer. To export the BOM in Fusion, you have to specify the file format.
Similarly, Inventor lets you export a BOM to a text or spreadsheet file, while AutoCAD Mechanical Toolset allows you to export a BOM to a .txt, .html, or .csv file. If you have used Creo to create your bill of materials from CAD files, you can export the BOM to a .csv or .html file.
Conclusion
Foundationally, the manufacturer will create CAD designs for the product. They will then generate the bill of materials from CAD files, with this BOM listing all the components that make up the product. By listing all these components, the BOM provides all the information a manufacturer needs to create it. Put in another way, the BOM serves as a manufacturing-ready parts list. This underscores the significant role that BOMs play in communicating product information.
