The Power of Metadata in CAD: Organization, Searchability, and Automation

Metadata provides useful information about a larger dataset. In CAD files, it includes details like file type, part number, creation and modification dates, approval date, drawing title and author. This metadata clearly outlines relevant details about a CAD file and its geometry, offering benefits such as improved organization, enhanced searchability, automation, and better traceability. 

It’s no surprise that most CAD software allows users to add metadata to drawings and files. But how have these applications implemented the concept of metadata? Beyond that, are there proven best practices for embedding metadata in CAD drawings? This article addresses these questions in greater detail and discusses the types and benefits of metadata, common pitfalls encountered when creating metadata, and more.

What is Metadata in CAD?

Metadata is a crucial concept in CAD file organization and management that refers to data that provides more information about a drawing, CAD file, or objects within the CAD file. Essentially, metadata describes other data, which more often than not exists in a much larger volume. This means metadata is smaller in volume than the data it describes.

You can think of metadata as something akin to a library catalog, which lists every book, magazine, periodical, and other documents in a library. Such a catalog is often extensive and, when digitized, allows bibliophiles to search for books by title, keyword, author, subject, and other criteria. Metadata powers this search function, which offers several benefits discussed later. Thus, embedding metadata in CAD drawings is a surefire way to enjoy these benefits.

Some examples of metadata of a CAD file or CAD drawings include:

• Part number or sheet number
• Drawing owner or creator
• Revision number or level
• Creator of the CAD file
• Date created or modified
• Approval date
• Location in the database
• Title of the drawing
• The name of the person who approved the drawing
• File type and size
• The application used to create or open the file

Types of Metadata in CAD

There are three types of metadata in CAD:

1. Administrative metadata: This metadata offers information that helps humans and computer systems manage CAD files. It describes information such as the access permissions, date of creation or modification, approval date, and status (e.g., approved or pending).
2. Descriptive metadata: This type of metadata relates to data assigned to geometry, geometric objects, or components in a CAD file, as well as the details that describe the CAD file. This metadata helps you track product or part information as well as data related to the file. Descriptive metadata can include the object type (e.g., a part or assembly), identifier (e.g., part number), object description, unit of measure, etc. It can also include the file name, drawing owner, drawing size, drawing number, revision level, and other relevant details.
3. Structural metadata: This type of metadata provides more detailed information about the relationships, types, and structures of data. Within the context of CAD drawings and documents, structural metadata describes the relationships between sub-assemblies and a product, a part and an assembly, or a part and a drawing, for instance.
4. Technical metadata: This type of metadata provides technical information about a CAD file. Examples of technical metadata include the file size, file type, software used to create the file, and storage location.

Benefits of Embedding Metadata in CAD Files

The benefits of embedding metadata in CAD files and drawings include:

1. Enables CAD file organization and management: It provides a structured method for naming and storing CAD files. By describing information such as the title, creator, date created and modified, and so on, metadata makes it easy for you to organize and manage CAD files. It also offers additional benefits. For instance, CAD file version control tools like product data management (PDM) software store metadata of the exact location of the main data. (These tools can also store the product data itself.)
2. Enhances search and filter: Recall our earlier comparison of metadata to a library catalog? Well, metadata enables designers and engineers to search CAD files by title, date created or modified, file type, creator, and more. It also allows them to filter CAD files, narrowing the pool of hundreds or thousands of files to just a handful.
3. Automates production: Metadata in a CAD drawing can indicate the status of a part. For instance, it can indicate whether a part has been manufactured or purchased and delivered. This information enables production to proceed to the next stage automatically and autonomously. The system overseeing production only has to read the metadata to give the go-ahead.
4. Improves traceability: Metadata provides a reliable paper trail of the dates a drawing was created, modified, revised, and approved, as well as the parties that performed these tasks. In addition, by capturing product information such as the part number, part description, the part superseding or superseded, and more, metadata enables teams to trace all vital information related to a CAD file and the design therein.

How to Add Metadata in Popular CAD Software

AutoCAD

AutoCAD lets you embed file-related metadata and object-related descriptive metadata, i.e., attributes. The former relates to data such as the drawing title, author, comments, subject, keywords, and the address for hyperlinked data. Here’s the procedure for embedding metadata in CAD drawings using AutoCAD’s Drawing Properties dialog box:

1. Click the Application button, select the Drawing Utilities option, and then click Drawing Properties. Alternatively, type DWGPROPS in the command line.
2. AutoCAD opens the Drawing Properties dialog, which contains multiple tabs including Summary, Custom, and more.
3. In the Summary tab, enter the useful metadata for each of the available fields.
4. Click OK to apply the changes.

AutoCAD’s Drawing Properties Dialog Box for Embedding Metadata in CAD Files (source)

To create an attribute definition, follow these steps:

1. Select the Define Attributes icon in the Block ribbon panel of the Home ribbon tab. AutoCAD will display the Attribute Definition dialog box.
2. Set the attribute modes, including:
   1. Visible or invisible attribute
   2.  Variable or constant attribute
   3. Single-line attribute or multiple-line attribute
   4. Movable or static attribute (relative to the rest of the block)
3. Enter tag information and text options
4. Specify the tag’s location
5. Click OK
6. Create a block and include the attribute in the selection set when AutoCAD prompts you to select objects for the block

SketchUp

SketchUp makes the process of embedding metadata in CAD drawings relatively straightforward. To do so, simply:

1. Hover the cursor over your drawing and select the component to which you want to embed metadata.
2. Press the right mouse button to open the right-click menu. Then, click Dynamic Components > Component Attributes. Alternatively, click the Component Attributes tool on the Dynamic Components toolbar or click Window > Component Attributes.
3. In the Component Attributes dialog box that pops up, select the Add attribute option by clicking the plus icon
4. SketchUp lets you add predefined attributes. Under the section titled “Component Info,” you will find four fields: Name, Summary, Description, and ItemCode. You may also add attributes related to position, size, rotation, form design, and behaviors. The software nonetheless allows you to enter a custom name for your own attributes by clicking the Or enter a custom name option.
5. Populate these fields with the associated information. It is advisable to add as much useful information as possible to support your colleagues as they use your product’s models.

Onshape

Onshape allows users to add, modify, or delete properties. A property in Onshape refers to the type of metadata. For instance, you can create a property such as part number, name, description, material, revision, and more. These properties will then be available for use by all members of your organization.

Properties/metadata Dialog Box in Onshape (source)

Here’s the procedure to create a new property in Onshape:

1. Navigate to the properties settings by clicking on your account user icon at the top right corner of the window.
2. In the dropdown menu that opens, click Company/Classroom/Enterprise settings.
3. Click the Create custom property button at the top of the page. This button is only visible to users with permission to create or modify properties.
4. Specify details such as the property’s name, property type (e.g., text, Boolean, integer, date, or list), publish state (e.g., pending, active, or inactive), and property attributes (e.g., description, default value, and unit type).
5. Add details such as the validation criteria for properties and the category in which the property will be made available
6. Click Create

You can access the properties by right-clicking a geometric object, which displays the context menu. You can then click Properties, which displays all the properties. 

SolidWorks

SolidWorks lets you embed metadata in CAD drawings. To do this:

1. Click File and on the dropdown menu, select Properties. This action opens the Summary Information dialog box. The dialog box has three tabs: Summary, Custom, and Configuration Specific. 
2. You can edit the fields in the dialog box or enter a new property. For instance, you can modify the property name, data type, and value. 
3. Click OK.

Summary Information Dialog Box in SolidWorks

While the Summary Information dialog box is a viable method for embedding metadata in CAD drawings, it involves a lot of tedium. For one, you must open the dialog box every time you want to modify the table. For this reason, another more straightforward approach is preferred. 

This approach involves using the Property Tab Builder, a standalone application that helps you create a customized interface for entering metadata into your SolidWorks drawings. As the name suggests, it lets you create a property tab that can be accessed from the toolbar on the right-hand side of the SolidWorks window.

Inventor

Inventor lets you add metadata to CAD files. This metadata pertains to the various properties associated with the CAD file, rather than the objects therein. Here’s the procedure for embedding metadata in CAD files using Inventor:

1. Click the File tab and choose the iProperties option. Alternatively, right-click the name of the part/model (at the top of the model design tree) and click Properties. Either of these actions opens the iProperties dialog box.
2. The dialog box comprises several tabs, including General, Summary, Project, Status, Custom, Save, and Physical. Visit each of these tabs and populate the various fields. The Project tab, shown in the image below, contains the fields for the most useful metadata for the CAD file and drawing. 
3. Click Apply > Close

Inventor’s iProperties Dialog Box for Embedding Metadata in CAD Files (source)

ArchiCAD

An ArchiCAD project typically comprises 2D drafting elements, 3D design elements, and metadata or non-visual data. 2D drafting elements include lines, labels, fills, dimensions, and images, while 3D design elements include MEP system elements, windows, doors, columns, and walls. Metadata in ArchiCAD includes acoustic specifications, properties, renovation status, classifications, and more. Classifications serve several functions, such as defining the properties available to an element, organizing project elements, and more.

To create, delete, or customize properties, use this procedure:

1. Click Options and select Property Manager, which opens the Property Manager dialog box. The dialog box displays all the properties as well as their data types and associated default values.
2. To create a new property, click the New button at the bottom of the window.
3. Type a unique property name and choose the group to which you want the property added.
4. Click OK.
5. You can also add details to the property whenever you click on any given property. For instance, you can add a brief description and specify the default value and data type.

Property Manager in ArchiCAD (source)

ArchiCAD also lets you assign classifications (via the Classification Manager).

Best Practices for Managing Metadata in CAD Projects

1. Describe data in a semantically consistent way: For instance, a part number should be made up of integers, while names can include both numbers and letters. This level of consistency allows the definition of key relationships, storage locations, and properties in a way that both humans and computer systems can understand. In simple terms, consistent definitions reduce confusion. 
2. Standardize naming conventions across projects: CAD standards and in-house CAD standard manuals ensure that designers, engineers, and other professionals follow the same, pre-approved rules and approach to creating CAD designs. Standardization increases efficiency, saves time, reduces the likelihood of errors, facilitates collaboration, and ensures consistency. It also offers a sense of identity. By standardizing the process of embedding metadata in CAD drawings, design companies ensure that their in-house teams use the same naming conventions from one project to another.
3. Create title block information and metadata as attributes or tags. Although it’s tempting to use notes for title block information, this approach is not recommended. Instead, you should create tags or attributes, which, by definition, offer descriptive information about the title block and are associated directly with the block.
4. Use templates: Templates are pre-configured with all the settings, metadata standards, and tags. Thus, using templates to create new CAD drawings helps you integrate all the settings defined in the former into the latter. Templates are, in fact, a proven method of propagating CAD standards.

Common Pitfalls and How to Avoid Them

The common pitfalls include:

1. Inconsistent metadata entries: Typos, inaccurate or outdated data, or mismatched properties are not uncommon. For instance, you may enter a property in the wrong field or enter the wrong part number. Getting around this problem is nonetheless quite easy. You simply have to be attentive whenever you are entering the data.
2. Failure to fully leverage metadata: Metadata can help teams automate workflows and production. But this is only possible if the metadata captures certain crucial information, such as the status of the product (i.e., whether it has been manufactured or delivered). Designers and engineers should fully utilize metadata features and ensure all relevant fields are filled to maximize benefits.

Conclusion

Metadata describes both CAD files and the objects they contain. This information ranges from the title of the drawing, file type and size, date created, modified, or approved, and the creator to the revision number, part number, and software used to open the file. Metadata generally helps you organize files more effectively. It also enables you to easily search and find the files you want. However, to reap all the benefits, there are a few considerations you need to take into account. You need to standardize the naming conventions, use semantically consistent descriptions/names, use tags and attributes, and make use of templates. It is also essential to ensure the metadata is error-free and captures all the details.