How to Open DGN Files in AutoCAD (Windows & Mac)

Opening and working with MicroStation DGN files in AutoCAD is a straightforward process on Windows. However, certain functionalities are limited on AutoCAD for Mac. This article outlines both the import and reference options for DGN files in AutoCAD, along with potential issues and recommendations to optimize the process.

How to Open DGN Files in AutoCAD (Windows & Mac)

1. Opening DGN Files in AutoCAD (Windows)

AutoCAD for Windows supports two ways to work with DGN files: importing them or attaching them as a reference (underlay). Here’s how to do both.

A. Importing a DGN File

When you import a DGN file into AutoCAD, the file is converted into a DWG format. Follow these steps:

1. Open AutoCAD and start a new or existing DWG file.
2. Enter the command DGNIMPORT in the command line or click the Application Menu (Big A) > Open > DGN.
3. Navigate to the location of the DGN file and select it.
4. In the Import DGN Settings dialog box, you can adjust the import options, such as model selection, conversion units, or handling external references.
5. Once the options are configured, click OK to import the file.

B. Attaching a DGN File as an Underlay (Reference)

Alternatively, you can attach the DGN file as a reference without converting it, keeping the DGN in its native format. This allows you to reference the DGN file without modifying it.

1. Open a DWG file in AutoCAD.
2. Use the XATTACH command or navigate to Insert > Reference > Attach.
3. Browse to the DGN file location and attach it.

2. Importing DGN Files in AutoCAD (Mac)

For AutoCAD for Mac users, DGN functionality is not supported. This limitation means that you cannot import DGN files or attach them as underlays directly in the Mac version of AutoCAD.

3. Key Features and Limitations of DGN Import in AutoCAD

While importing DGN files into AutoCAD, the program translates basic data like lines, arcs, and polylines into DWG objects. However, there are known limitations:

• Data approximations: Text, dimensions, and color properties might not translate exactly as they appear in MicroStation.
• Lost object properties: Multilines, line styles, or certain custom elements might not display correctly.
• Symbols and colors: DGN symbols that have specific color properties may lose their color during import.

Additionally, DGN files with complex objects may not convert as expected, and certain data features will be visually approximated. For instance, multiline styles may not import correctly, and DGN line styles in non-uniformly scaled blocks may appear differently in AutoCAD.

4. Best Practices for Importing DGN Files

To improve compatibility and ensure that the data translates properly when importing DGN files into AutoCAD, consider these tips:

• Minimize custom elements in the original MicroStation file.
• Use TrueType fonts instead of SHX fonts in text elements.
• Simplify dimension and hatch styles for more accurate translations.
• Ensure the DGN file is cleaned of unnecessary objects or references.

For better results, request that the MicroStation user sending the file use ByLevel settings for colors and line styles, and limit the use of custom patterns.

5. Importing Referenced DGN Files

If your DGN file references other DGN files, you can import those references as either blocks or external references (Xrefs). To ensure that these references are handled correctly:

• In the Import DGN Settings dialog box, check the options for converting references to blocks or Xrefs.
• Alternatively, you can import each referenced DGN file separately and manage them in AutoCAD.

6. Converting Units When Importing DGN Files

Ensure that the drawing units in the DWG file match the master or sub-units of the DGN file for accurate conversion. For instance, if the DGN file’s master units are in meters and sub-units in millimeters, set the DWG units to meters to prevent scaling issues.

7. Exporting DWG Files to DGN Format

You can also export DWG files back to DGN format (V7 or V8 versions). To do this:

1. Enter the DGNEXPORT command or go to Application Menu > Export > DGN.
2. In the Export Settings dialog, specify your preferred options for translating DWG layers to DGN levels and handling external references.
3. Select the V7 or V8 DGN format based on your requirements.

Limitations in the export process can include:

• Loss of dynamic blocks and AEC objects.
• Visual approximations of text styles, dimensions, and colors.

8. Managing DGN Mapping Setups

To control how DGN properties are translated into DWG properties, you can create or modify DGN mapping setups. This allows you to define how elements like layers, linetypes, and lineweights are translated between formats.

To manage DGN mapping setups:

1. Enter the DGNMAPPING command to open the Mapping Setup dialog box.
2. Here, you can create new mapping setups or edit existing ones to fit your CAD standards.

Conclusion

Working with DGN files in AutoCAD is made simpler through the import and reference tools available in Windows versions of AutoCAD. However, Mac users need to explore alternative solutions as native DGN support is not available. By following best practices and addressing the limitations, you can optimize the conversion process between DGN and DWG formats, ensuring the integrity of your data during transitions between MicroStation and AutoCAD.