We all know about bill of materials in general and in SolidWorks. But very few understand what the different types of bill of materials are, why are they important and how do we make one in SolidWorks properly. Getting your bill of materials right is an crucial step in ensuring that your product is manufactured correctly and is not missing any part.
What is a Bill of Materials in SolidWorks?
Bill of materials (BOM) is the complete list of all the items that are required to build a product or a part of the product. BOM includes all the parts, subassemblies, assemblies, components and raw materials that manufacturing a product involves. Bill of materials also includes the quantity of every mentioned item. BOM in SolidWorks is essentially your basic ‘recipe’ with all of the ‘ingredients’ required to build your project.
CAD modelling software such as Autodesk Inventor, SolidWorks, Catia all includes the ability to make a detailed bill of materials. However, as compared to all the CAD modelling software in the market today, SolidWorks has more options and BOM types that can be created with ease.
How to Structure a Bill of Materials in SolidWorks?
A bill of materials is hierarchical. The completed product sits at the top of the list, while costs, part description, quantities, product codes and other specification come afterwards.
The most common representation of the bill of materials in SolidWorks include;
Single level BOM
Single-level bill of materials is a simple list of a product. Each subassembly or assembly only appears once. Single-level BOM in SolidWorks is quite easy to make but is not suitable for complex products as a single level BOM makes it hard to identify individual parts from one long list.
Multilevel BOM
Multilevel BOM is more involved and detailed as compared to the single-level BOM. Though it takes more time and efforts to make a multilevel BOM, it provides much more specificity and detail on the parent and child parts of the assembly.
Why is a Bill of Materials Important?
Bill of materials is the basis of production planning systems. The information contained in the bill of materials has all the information for manufacturing resource planning (MRP) and product costing. The BOM tells the manufacturer the parts and materials required to make a particular product. Engineers working on 3D CAD models of products in SolidWorks ensures that the BOM is made as accurate as possible to ease out the manufacturing process.
Types of Bill of Materials in SolidWorks
There are many different types of BOM that can be made. There are three specific types of BOM that SolidWorks makes well;
- Engineering bill of materials
- Manufacturing bill of materials
- Sales bill of materials
Engineering Bill of Materials
Engineering bill of materials also commonly referred to as EBOM specifics parts and assemblies that are designed specifically for the engineering department. An engineering bill of materials in SolidWorks shows the component structure from a functional point of view and has mechanical or technical drawing of the product.
An engineering bill of materials in SolidWorks is structured from the design standpoint. High accuracy in EBOM is critical as incorrect engineering BOM can translate into incorrect inventory levels, needless revision cycles, incorrect product costs and production issues.
Manufacturing Bill of Materials
Manufacturing bill of materials also commonly referred to as MBOM includes a structured list of all sub-assemblies or items that are essential to produce a shippable completed product. Manufacturing bill of materials made using SolidWorks in addition to presenting all the information on individual parts will include the information on the parts requiring processing before assembly.
Sales Bill of Materials
Sales bill of materials also commonly referred to as SBOM has all the information about a product in its sales stage. The data in the SBOM has the details of the product before its assembly. In a sales bill of materials, the finished products appear as separate entities under the sales order document. SBOM developed in SolidWorks comes in handy when dealing with spare parts orders or helping the customers identify the faulty part.
How to Create a Bill of Materials in SolidWorks
You can insert a bill of materials easily into your drawing of an assembly using SolidWorks. You can insert table-based BOM into an assembly or a single part or both in one. In SolidWorks, when you add or remove any component from an assembly, the bill of materials will automatically update and reflect the changes.
To automatically update the BOM, you have to select the ‘Automatically update of BOM’ option in Tools > Options > Document properties > Tables > Bill of Materials. Doing so will automatically update your BOM whenever you add, delete, replace components, change names, custom properties and so on.
If you do not select the ‘Automatically update of BOM’, you can still create a manual bill of materials in SolidWorks. Whenever any changes are made in the components, you must delete or re-insert the BOM have an updated one.
Microsoft Excel-based bill of materials can also be inserted in your SolidWorks drawing. To do so, you must have Microsoft Excel installed on your computer. SolidWorks supports Microsoft Excel 2007 onwards. SolidWorks has several built-in BOM templates to choose from. These templated can be accessed from drive letter:\Program Files\SOLIDWORKS Corp\SOLIDWORKS\templates.
The default template Bomtemp.xls or bom-standard.sldbomtbt for Excel-based bill of materials includes the part number, Item no, quantity and description columns. You can add custom properties into the parts of your assembly to take advantage of additional columns into these templates.
Promoting Components in SolidWorks Bill of Materials
When inserting the BOMs in your SolidWorks drawings, there are three different options of how the parts and subassemblies will be displayed in the table. The type of BOM can be Indented, Parts only, or Top-level only.
Top-level only
This level shows all the items listed in a collapsed feature manager of the assembly. The top-level BOM shows the parts and subassemblies, but not the components that are present under these subassemblies. This BOM type gives an overview of what parts are used in the product. Such BOMs are usually the smallest as compared to other BOM types.
Parts Only
The ‘Parts Only’ BOM shows every part file in the assembly. This includes all the top-level components and parts that are in the subassembly, including the parts that are several levels deep. The subassemblies present in the drawing are not shown in this BOM type.
Indented
Indented bill of material is a hybrid of both ‘top-level only’ and ‘parts only’. It displays everything at the top level and also has expanded subassemblies along with the parts listed under them. Usually, the indented BOM has the biggest BOM as compared to the previous two.
How to Insert Bill of Materials for a Particular Drawing
To insert a BOM into a SolidWorks drawing;
- Click on the ‘Bill of Materials’ from the table toolbar, or Insert > Tables > Bill of Materials
- Select the drawing view to specify the model
- Using ‘Property Manager’, set the properties of the BOM, then click OK
- If the option, ‘Attach to anchor point’ is not selected, click in the graphics area to place your bill of materials table.
What is Included in an Effective BOM?
One of the main functions of bill of materials is to ensure that the products are built the way they are meant to be built, therefore, it is best to include specific information regarding the product in the BOM data.
Here is a list of information that is ideal to be included in your bill of materials when creating it using SolidWorks.
Part number
Assign a part number to each part and the assembly to reference and identify the parts easily and quickly. Part numbers assigned by manufacturers are either in intelligent or non-intelligent numbering scheme. Both these numbering formats have their pros and cons. While assigning part numbers, it must be ensured that multiple part numbers are not assigned to the same part as this may create confusions and inventory mismanagement.
BOM level
It is crucial to assign your parts and assembly in SolidWorks with a number. This helps the users to identify where the parts and assembly fits into the hierarchy of the SolidWorks BOM.
Part name
Names of common parts such as screws and nuts are automatically labelled from the SolidWorks library. The parts that are made in SolidWorks itself should be given a unique name. This enables you to identify your part quickly and easily.
Phase
Though not necessary, it is a good idea to record at what stage each part is at in its lifecycle. For example, the parts that are under production, you can use term like ‘In Production’ to indicate the stage of the part. This is extremely useful when introducing new product to the market as it allows you to keep track of your part/assembly and create realistic and manageable project timelines.
Quantity
Record the number of parts used in assembly to help guide the purchasing and manufacturing activities and decisions.
Description
This column includes a detailed description of each part in the drawing to help the reader distinguish between similar parts.
Unit of measurement
It helps classify the unit of measurement in which a part is designed and manufactured. Unit of measurement includes standard measurement units such as feet, inches, yard and meters. The unit of measurement in SolidWorks bill of material must be consistent throughout the drawing. Part manufactured with different unit of measurement will have inconsistencies between them.
Reference designator
Reference designator is an important element in SolidWorks BOM if your product contains PCBs (Printed Circuit Boards). The reference indicators tell the reader where that particular part will fit in the circuit board. Having this information in the bill of materials can help avoid confusions and save time down the road.
BOM notes
BOM notes in SolidWorks help the designer put other relevant notes to keep everyone who interacts with the BOM on the same page.
Procurement type
It helps determine how each part is purchased or manufactured to enable efficiencies in planning, manufacturing and procurement activities.
What is OpenBOM Add-on for SolidWorks?
OpenBOM is one of the most commonly downloaded add-on for SolidWorks. Though making bill of materials in SolidWorks is quite simple and easy, the BOM generated by SolidWorks at times is not sufficient to calculate the mass, cost or plan purchasing.
OpenBOM add-on enables the users to make BOM that includes information about usages, parts and other business information such as cost and supplier. OpenBOM add-on for SolidWorks is free.
Conclusion
Creating bill of material in SolidWorks is not only a necessary step from the product development point-of-view, but it also turns your product design into a reality. Before creating a BOM for your product, it is important to consider all the information that you will utilize in your SolidWorks BOM and how you will manage all the associated product documentation.
