Many designers, manufacturers, and architects still work with CAD software such as Autocad to create their designs. Using these CAD files as a reference or underlayer for our Revit model is often a good idea, but that means that we need to import those CAD files into Revit.
When importing the CAD file, you can choose between importing it directly or linking the file. This decision is crucial because it can change the performance of the Revit model. And besides importing and linking is it also important to clean up CAD files before importing them into Revit.
Table of Contents
In this article, we are going to take a look at how to prepare a CAD file before importing it into Revit, including managing multiple linked CAD files and how we can visually change them with Visibility Control. In addition, I will give some extra tips you can use after linking the CAD files.
Importing CAD Files
Before we start heading on how to import CAD files into Revit it’s important to know the difference between importing the file directly or linking. Most experienced Revit users, including myself, will tell you not to import DWG files but to link them to your project.
The reason why you should consider linking files over importing is that when you import, it will bring unnecessary settings from that file into your Revit project. You can think of Line Styles or Fill Patterns, for example.
In the worst case, importing CAD files directly into your Revit model can significantly decrease its performance and unnecessarily increase the file size. When linking a DWG file, it will load the latest versions when opening the Revit file, making it more efficient to manage the files outside Revit.
Note
There is no difference between import CAD directly or linking in Revit if it comes to Line Patterns. In both cases it will bring them into your project. The Line Patterns will start a name with: IMPORT.
Preparing the DWG
Whenever you start to import or link a DWG file to Revit, it is important to prepare the file and clean things up. Start by duplicating the DWG file you received and keep the original just in case. You can use a special subfolder for example to organize the files that you have cleaned. Take the following steps to manage and clean the DWG files.
1. Bind Xrefs
While Xrefs in DWGs can cause issues in Revit while linking, you can either bind the Xrefs or detach them which will delete the Xrefs from the file. This setting will prevent you from duplicating Line Patterns, Layers, etc. Open the file in Autodesk Autocad and follow the next steps:
- Type the command XREF and press enter > External Reference dialog box will open
- Select the files you wish to Bind or Detach > Right-click on selected files to open the menu
- Choose either Bind or Detach based on your specific requirements
2. Layer Control
For layer control, you can use different options to clean the DWG file.
The first option is to use the command: SETBYLAYER. This option allows you to remove all different overrides such as line types, line weight, and colors. The command does reset all objects to the original that has been set in the layer.
The second option is to Freeze layers you do not need in Revit after linking.
The third option is to Delete unnecessary layers, which removes all lines and blocks. You can either delete them in the Layer Properties Manager or use the command LAYDEL + N.
3. Overkill
The OVERKILL command in AutoCAD allows you to clean all overlapping and duplicated geometry such as lines.
4. Purge
To remove all unused layers, blocks, groups, different styles, etc. we can use the PURGE command. Follow the steps below to clean all unnecessary and not used items.
- Enter the PURGE command in AutoCAD > Purge dialog box will open
- Select all items or select them individually
- Choose either Purge Checked Items or Purge All depending on your requirements
- Confirm your Purge
5. Audit
Lastly, before you save the file you just cleaned up, you can use the AUDIT command to check for any errors that are left in the file. After entering the AUDIT command type Y to fix any errors that are detected.
Import CAD to Revit
Once you have finished preparing and cleaning the DWG files, you can start linking the files to Revit by following the steps below.
- Open the Insert tab
- Click on Link CAD in the Link panel
- Browser to file location and select a DWG file
- Select Current view only, or uncheck when you want the DWG to appear in other views.
- Choose different import settings (use settings from PrintScreen for best default settings)
- Press Open > Place DWG on view by clicking the left mouse button
Import Settings Explained
When you Link CAD files to your Revit project, you can adjust some options, such as Colors, Layers/Levels, and positioning before you import the CAD file into Revit. As I mentioned earlier, you can use the default settings in the PrintScreen above for the best results. In the table below you can see a summary of what each setting does.
| Import Option | Description |
|---|---|
| Current view only | This feature allows you to link a DWG file to a specific view in Revit when checked. If unchecked the linked file will be visible in all views. |
| Colors | The Colors option has three different options to choose from, which are: Invert, Preserve, and Black and White. Invert: By default Revit will invert the colors of any lines and text objects which means that dark colors become lighter and vice versa. For some users, this option can improve the readability of the file in Revit. Preserve: As the word already says it will preserve the colors as defined in the imported file. Please note that some of the RGB colors of the imported file may not be an exact match to the original file Black and White: This option will import the file in black and white. I recommend this setting as default because it will improve the readability a lot. |
| Layers/Levels | This option allows you to choose which layers should be imported when linking. There are a total of three different options to choose from, which are: All, Visible, and Specify. All: This default option will link all layers. Visible: When selecting this option, you will import all visible layers. Layers that are frozen in the DWG file won’t be linked. Specify: This feature allows you to select the Layers/Levels before linking. The deselected layers will be deleted. |
| Import units | You can set the units of measure for linking the DWG file by selecting from different predefined units. The values you can choose from are: Auto-Detect, feet, inch, meter, decimeter, centimeter, millimeter, and Custom factor. |
| Correct lines that are slightly off axis | This option is enabled by default, and it will automatically correct lines that are slightly off-axis within a range of fewer than 0.1 degrees. This can prevent issues with Revit elements that are generated from those lines. Note: When you link site plans, it is better to uncheck this option so it will not autocorrect any of the lines to be more accurate. |
| Positioning | To position the linked file you can choose from: Auto – Center to Center, Auto – Origin to Internal Origin, Auto – By Shared Coordinates, Manual – Origin, and Manual – Center. Auto – Center to Center: Place the center of the linked file at the center of the Revit model. Auto – Origin to Internal Origin: Place the origin of the linked file at the origin of the Revit model. Auto – By Shared Coordinates: Place the linked file in the Revit model based on shared coordinates. Manual – Origin / Center: Selecting this option allows you to place it manually with the cursor placed at the origin or center of the linked model. For both manual options, you have to move the cursor to adjust the position and then left-click to place it inside the view. |
| Place at | This option allows you to select a level in the model to position the linked DWG. This level will be the base level of the file. This will only be available when Current view only is unchecked. |
| Orient to View | The Orient to View option can be used to orient the linked DWG when the True North and Project North of the project are not aligned. In case the view is set to True North, but rotated away from Project North, you can uncheck this option to align the DWG file to Project North. When both True and Project North are aligned this option has no effect. This will only be available when Current view only is unchecked. |
Note
When you import data from a CAD file into Revit to create a toposurface, it is important to include the 3D information. Therefore, it is important to uncheck the Current view only option.
Import CAD to Revit workaround
Sometimes you really have to import the CAD file into Revit instead of linking, which can be the case for details, for example. To minimize the import of unnecessary items, it’s recommended that you clean up the DWG file prior to importing it. Nonetheless, it’s worth mentioning that there are some “workarounds” that you can use to avoid issues with your Revit file.
- Create a Model In-Place and then import the CAD file into the Model In-Place editor
- Create a Family and Import the CAD file there > Load into Project
For either of the approaches, the category you select doesn’t make much difference, although the Generic Model is the most commonly used for this.
Note
You might also like this article: How to Import Excel into Revit.
Managing Linked CAD Files
In Revit, it is possible to manage files after linking. Inside the Manage Link feature, you can Save Positions, Reload, Unload, and add new files by linking. Follow the steps below to manage individual or multiple files at once.
- Open the Manage tab
- Click on Manage Links in the Manage Project panel
- In the Manage Links dialog box open the CAD Formats tab
- Select the linked files you want to manage
- Choose any of the options to manage (Reload, Unload, Remove, Add)
Manage Links options
In the table below you can find all possible options which you can use to manage the Linked CAD files.
| Manage Link Option | Description |
|---|---|
| Save Positions | When you apply Shared Coordinates to a linked file, it will check the Position Not Saved box. From the Manage Link settings, you can now Save Positons to the linked CAD file. An alternative way to preserve the Positions of linked files is by saving the Revit project, which will prompt this option. |
| Reload From… | Whenever you change the file location of your linked files, you can use the Reload From… option to relink the CAD file again. |
| Reload | The Reload option allows you to “Refresh” the CAD file after making adjustments to it. |
| Add… | The Add… option allows you to Link CAD files from within the Manage Link panel. |
| Import | Using the Import option will bind the Linked file to your project, which is not recommended. |
| Unload | To temporarily remove the CAD file from your project. (Use Reload to make it visible again). |
| Remove | This option will remove the CAD file permanently from the Revit project. |
Tip
Revit can preserve changes made to the graphic display of linked CAD files when reloading them, by checking the Preserve graphic overrides. This applies to all linked CAD files in the project. Unchecking this option will discard all graphical overrides while reloading the file.
Visibility Control Linked CAD File
After you have imported or linked the files, you have the possibility to change the visuals of the lines. This can be done in two different ways: Object Styles, or Visibility/Graphics. Object Styles will change the appearance of the lines of all views (project-wide), whereas Visibility/Graphics only change the appearance view-specific.
Object Styles
- Open the Manage tab
- Click on Object Styles in the Settings panel
- In the Object Styles dialog box open the Imported Objects tab
- Change Line Weight, Line Color, Line Pattern, or Material
Visibility/Graphics
- Open the View tab
- Click on Visibility/Graphics in the Graphics panel
- In the Visibility/Graphics Overrides dialog box open the Imported Categories tab
- Choose a layer to change the appearance
- Click on Override…
- Change Line Weight, Line Color, or Line Pattern
Extra Tips
After you import or link the CAD file into Revit, you can use some of the tips below to manage the CAD files.
Query Tool
Revit has a nice feature called Query, which can be used after linking or importing a CAD file. This tool allows you to hide or delete layers/levels individually.
- Select the imported CAD file in the view
- The Modify | DWG tab will show up > Import Instance panel > Click on Query
- Select any of the lines from the imported CAD
- In the Import Instance Query choose to Delete or Hide in view
Tip
Use the Delete Layers in the Import Instance panel to delete multiple layers at once.
Draw order Instance Parameter
When you link or import a cad file with the option: Current view only, you can change the Draw Layer of that file, which changes the order. You can click on the file and then go to the Properties Browser > Go to Draw Layer > Change to Background or Foreground. An alternative way is to go to the Modify panel.
Note that when you do not use the Current view only option the Draw Layer will not be available.
Wrapping Up
Keep in mind that it’s important to prepare and clean up the DWG file before importing or linking it into Revit. Linking a DWG file is recommended over importing to avoid bringing unnecessary settings into the Revit project. After you have prepared the CAD file, you can link it to Revit and Adjust the import/link settings such as colors, layers/levels, and positioning.
I hope this article helped you to understand how to import or link CAD files into Revit. If you have any questions, just drop a comment below.
