- Creating a combined Mechanical and Electrical Bill of Material. With mechanical and electrical design work often carried out by different individuals and with different systems, it’s difficult to create a single unified electro/mechanical bill of material (BOM). SOLIDWORKS Electrical 3D enables a single BOM to be created automatically within.
- BOM control/process between mechanical and electrical. All you need is a SOLIDWORKS ID, or new or existing 3DEXPERIENCE ID. So we're currently using only Electrical 2D and regular Solidworks 3D for design. This ends up in parts being called out twice, in mechanical prints and electrical schematics.
- Extract catalog information from the project to create a Bill of Materials report. Using AutoCAD Electrical, you can perform a project-wide extract of all BOM data found on your project drawing set. The data is extracted from the project database, matched with standard entries in the catalog database, and then additional fields are pulled from the catalog files.
AutoCAD Electrical BOM Report. This project supports the paper: Aubrey L. Woern, Joseph R. McCaslin, Adam M. Pringle, and Joshua M. RepRapable Recyclebot: Open Source 3-D Printable Extruder for Converting Plastic to 3-D Printing Filament.
I’ve been fortunate having been given the chance to talk to many manufacturing companies ranging in size from small hardware startups to large manufacturing companies. In having done so, I’ve learned much from asking people about Bills of Materials, or BOM. Doing so exposes much about how a company designs, manufacturers, and services its products.
As an engineer, you may have asked yourself why are BOMs such complex data structures. Or perhaps, you simply take for granted BOMs are a fact of life and deal with them best as you can. In this post, I will try to give you a greater understanding of BOMs and perhaps if you don’t already do so, appreciate them for what they are: the core of all manufacturing processes.
Bill of Materials, or BOMs, are the core of all manufacturing processes.
Engineering BOM is typical the beginning of any Bill of Materials management activity. Based on my observations, there are three aspects in which engineers are involved with engineering BOM management:
Part List. A part list is a simplest way to manage an engineering BOM. Usually done by exporting information from a CAD system and adding non-geometrical items. It’s a typical way to create a list of parts that can be used for ordering purposes and/or communicating with contractors.
Structure transformation. A CAD structure is not an engineering BOM. Restructuring is one of the most complicated processes when creating an engineering BOM. In my experience, this process can not be easy automated (if at all) demanding much human involvement. Mapping between data structures is hard and referencing between structures is even harder. However, structure transformation is absolutely important to the process of correctly creating an engineering BOM.
Configurations. Most products today demand configurations such as models, options, etc. The management of these configurations in a CAD system is complex and confusing. If you try to apply configurations to a structure transformation, chances are you will get lost. The best results can be achieved if a tool used to manage engineering BOMs is capable to model configuration. However, this is often not the case and as a result, companies end up with many complex spreadsheets.
BOM management remains a challenge in most manufacturing organizations. Let’s now try to understand the elements of a BOM that influence the engineering activities. I’m familiar with four BOM related elements that are the lifeblood of most product development processes.
BOM and Part Lists
A Bill of Materials is at heart a list of all the items required to make a product. BOMs include components, raw materials, and sub-assemblies. They may also include intermediate items identifying in-process elements to facilitate planning and other manufacturing processes. Depending on the industry people refer to BOMs differently. For example, in the process industry, it can be called a recipe or formula. A Part List is usually a term used to refer to a single level list of a specific level of an assembly or sub-assembly.
Part Number
Part Numbers is one of those terms that is very tricky to define; there are entire product development and BOM management stories and histories behind it. I’ll try to keep it simple with a short definition: a Part Number (PN) is a unique identifier that identifies a single object in a Bill of Materials. The trick in naming them, however, is defining an object and keeping it consistent with your internal processes. Assigning part numbers is often complicated and a big topic of discussion in manufacturing companies. A short list of issues often discussed around the part numbering process include the traditional definition of FFF (Form, Fit and Function), interchangeable parts, substitute items, and special parts, to name a few.
Routing
Consider a navigation system with roads between different places of interest. Now imagine part numbers. Routing is a roadmap that defines the path of part numbers across the manufacturing floor by specifying workstations and labor time associated with every station. Routing is usually applied to manufactured parts or items.
Drawings
Historically, drawing are where people put the BOM for a product, sometimes solving the problem of BOM distribution within a company. However, a BOM in a drawing presents many disadvantages. In most situations, people don’t need a drawing, rather, they need a BOM and/or part list. Another point of confusion is the discussion about applying part numbers in drawings. In most situations, this represents the limitation of systems used for product development, e.g., PDM, PLM. Separating Part Numbers and Document Numbers is the most reasonable way to manage the confusion of BOMs in a drawing.
For the last few decades, the importance of contract manufacturing has increased significantly. It affects many engineering activities. A BOM is one of those tools that are very important and can help you optimize and streamline contract manufacturing activity; something I’m seeing more and more of. Perhaps this is something you deal with on a daily basis.
Globalization and contract manufacturing are two important trends shaping modern manufacturing. Companies are using contract manufacturers (CM) for different purposes: design, component supply, assembly, fabrication, etc. So, what are the critical elements of a BOM system capable of supporting your CM processes? Here’s what I’ve learned:
- Access to CAD components and libraries. Having information about components, availability, cost and other parameters such as regulation is critical. To replicate this information in your BOM system is possible, but not reliable and not scalable. Check if your BOM system can access this information and automate both the import and export of data to avoid manual data entries.
- Flexible and granular BOM management. You need to organize BOMs in such a way engineering and CM will be able to access them. Doing so will allow early access to all parties involved in design and manufacturing to access product information.
- Change management. When it comes to BOMs, change happens. All the time. It will happen to your design and manufacturing plan. Find a BOM tool that allows you to manage the traceability of changes alongside manufacturing plans.
- Collaboration. You need to have the right technology in place to enable your CM and subcontractors to access information in your BOM at any time. You’ll need all the other three aforementioned points to create a reliable “everyone on the same BOM” that cuts down on mistakes and errors while holding all distributed stakeholders accountable.
I’ll close this post with a few tips I’ve learned along the way of how to optimize BOMs and my thoughts on the proverbial Engineering BOM (EBOM) versus the Manufacturing BOM (MBOM). Now that you have a better understanding of BOMs, here are few ways to optimize them:
Function Oriented BOM
By definition, a BOM is not strictly functional. However, in my view, there are many BOMs in organizations which reflect their “product structure” as the main driving force behind how their BOMs are organized. As a result of this, many companies experience difficulties with operations and processes that involve these BOMs. This can be remedied if you think of the BOM from a functional standpoint. The form of a BOM follows functions. Ensure that the final form of your BOM reflects what you want the BOM to do. Your BOM tool should be sufficiently flexible to allow this.
Wide Company Usage
Very often BOMs start in the engineering department. Compartmentalized organizational logic made BOM separation natural. However, when you start planning cross functional processes, managing BOMs become a big challenge. I suggest you include the high-level business view in a BOM by structuring it around end items that capture both the product you are creating and the processes involved in manufacturing it. Stay away from silo thinking.
Part Numbers and Documentation
Don’t mess with these two main groups of identification parameters. Don’t try to combine them. Build BOM around part numbers and think about how to simplify the relationships between Parts and Drawings. The complexity of these relationships will make your future change process messy and complicated. Traditionally, BOM ends up in the drawing sheet. It was in the past. With massive adoption of 3D CAD systems and computer automation, you can re-think it. Managing part numbers is a separate topic that I will address in another post.
Modules and Flattening
Use grouping techniques to create part of BOM that can be easily handled and replaced. Use logically combined parts that belong to specific configurations. It will help you to simplify your ordering system. Modern tools allows you to deal with hierarchies much easier. However, think twice before you introduce an additional level in BOM hierarchy. Flat BOM is much easier to handle. It is very important to create a BOM structure that allows you to run change processes as easy as possible. Analyze your change processes upfront.
EBOM vs. MBOM
From a technical standpoint, it is relatively easy to explain the difference between EBOM and MBOM. The first (EBOM) represents the way a product is designed (structure, models, functionality, configurations, etc.) The variety of characteristics depend on the type of manufacturing and processes. Manufacturing BOM (MBOM) defines how a product will be produced (including aspects of material ordering, routing, different manufacturing plants, etc.).
EBOM and MBOM are not entirely different but data structures and attributes used in both often do not overlap. Some engineering attributes and structures are not relevant for an MBOM. On the other hand, MBOM information is often irrelevant and not needed by engineers and designers.
The thing that makes everything complicated is the process between the EBOM and MBOM worlds. The “throw over the wall” manufacturing concept co-exists together with the tightly collaborative process of work on EBOM and MBOM. Engineers request information about the product (EBOM) as early as possible in the development cycle. At the same time, manufacturing planning can get back to engineering in order to finalize and optimize the product. It’s best to ensure your BOMs are optimized to increase the effectiveness of both engineering and manufacturing.
Bill of Material is an important topic and it is the lifeblood of all product development processes. Modern manufacturing trends such as globalization, contract manufacturing, mass customization, IoT, and many others are increasing product complexity and demand more sophisticated and connected tools to help engineering and manufacturing companies to work together.
This post reflects some basic aspects of BOM management for engineers. Please let me know what you think. There are plenty of other BOM related topics I didn’t get into here but would love to do so in future posts.
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If you are starting a small business that manufactures or assembles products, you are going to need to create and maintain a bill of materials (BoM) for your products. Just like a cook has a recipe and list of ingredients, if you are designing, selling, or servicing a product, you need some instructions and a list of materials. Although you may eventually need to use more advanced inventory control software or a full-fledged MRP system, you can get started using our free Bill of Materials template below and customize it as needed.
Download
⤓ Excel (.xlsx)⤓ Google SheetsLicense: Private Use (not for distribution or resale)
'No installation, no macros - just a simple spreadsheet' - by Jon Wittwer
Description
This bill of materials spreadsheet was designed originally to identify the parts needed for various custom LEGO® designs. But then I added a few other features, such as a revision history worksheet, to make the template more general.
Most people could easily create their own bill of materials spreadsheet from scratch, but hopefully this template will provide a useful example. It may not always be possible or desirable to include photos or images, but when applicable, pictures can be tremendously useful. See the example BoM below.
Google Sheets Version (Added 4/12/2019): This version implements the new Image in Cell feature. The template includes a Parts List worksheet and you can insert an image of each part. In the Bill of Materials worksheet, after you select the Part ID the rest of the info is displayed automatically, including the image, using VLOOKUP formulas. Awesome!
What is a Bill of Material (BoM)?
Put simply, a bill of materials (BoM) is a listing of the materials and parts used to manufacturer some product. Each material in the list should include the quantity needed and a unique part number that can be used to identify the exact part or material to acquire from the supplier. Additional information (such as the cost, description, revision history, photos, and supplementary characteristics) may be included in a BoM, or that information may be available elsewhere (using the unique part number as the reference).
For complex products, some of the parts listed in a bill of materials may be sub-assemblies that each have their own BoM as well. For larger companies or more complex products, the BoM is a crucial part of a larger MRP System (Material Requirements Planning), and would generally be integrated into the MRP software. In these cases, the MRP system might be able to export the list to an Excel spreadsheet, but you would generally not be using the spreadsheet directly to make changes or revisions in the system.
Using a Spreadsheet-Based BoM in Practice
It's very easy to use the above template to create a bill of materials for a single assembly. But, as your product(s) become more complex, you'll quickly run into the following problems:
- Security and Access Control - Using spreadsheets as your primary data source for process definitions can lead to problems when it comes to security, giving people different access privileges (viewing vs. updating), etc.
- Change Management - What happens when an engineer makes a change to their bill of materials but the manufacturer is still using an old copy of the spreadsheet? These types of errors are difficult to avoid without using a central primary database for storing, viewing, and tracking product data. A BoM spreadsheet file is not much different than having a printed copy of the materials list: out-of-date lists could be floating around in cyberspace. If you are going to use a spreadsheet BoM system, make sure you also set up a system for managing changes and revisions to ensure that the information is accurately updated throughout the process.
Because of these limitations, I want to be clear that I'm not advocating the use of BoM spreadsheets for every circumstance. However, the bill of materials template can be very useful when you want a quick solution.
Bill of Material Example
The 'Example' worksheet in the Bill of Materials template above shows the parts needed to make a custom mini Star Wars X-Wing® design with LEGO® bricks. I'm using this as an example because it shows how useful the parts list can be when images of each part are included.
LEGO® enthusiasts keep reading ...
The LEGO Digital Designer software allows you to create virtual assemblies of LEGO bricks and then export the bill of materials to a spreadsheet. That is where the images came from in the example. The software will also automatically produce the assembly instructions. The purpose of the BoM is to help you acquire the needed pieces.
If you are your kids enjoy designing custom LEGO creations, you probably know that the main limitation is not having the right pieces. Luckily, the lego.com website lets you purchase individual pieces using their Pick a Brick service, and although you can't get every possible piece in whatever color you want, it is pretty amazing how many pieces are available.
Resources / References
- Bill of Materials at wikipedia.org - Information about what a bill of materials is and the various types and uses.
- Definition of Bill of Materials at searchmanufacturingerp.techtarget.com - A good general definition.
- Using Excel for Bill of Materials at arenasolutions.com - Lists and explains the pros and cons for using a spreadsheet-based bill of materials (BOM). Includes an example Excel BOM download. They're obviously promoting their BOM system that is part of their PLM (product lifecycle management) tool, but the site still contains some really good information.