About Exporting MicroStation DGN Files

You can export DWG files to the V7 DGN and V8 DGN drawing file formats.

The export process translates basic DWG file data into the corresponding DGN file data, and specialized data as a best fit. There are several translation options to determine how data is translated during the export process. For example:

• How external references are handled
• How the dynamic range of the DGN file as controlled by the master and subunits are specified
• Whether the DGN file should accept data with nonzero Z coordinates

The export process uses a standard mapping translation by default, which maps DWG-format layers, linetypes, lineweights, and colors to DGN-format levels, linestyles, lineweights, and colors. If necessary, you can change the mappings to match your company CAD standards. You can edit the mappings with the DGNMAPPING command.

Understand the Limitations

AutoCAD objects and properties that have a direct correlation to DGN objects and properties are exported without any issues. For example, AutoCAD layers are translated directly to MicroStation levels. However, AutoCAD objects and properties that have no direct correlation to DGN objects and properties will not translate with full fidelity. The following are known limitations that result.

• Data with built-in features or variations are visually approximated. For example, text and dimensions with specialized formatting and customized color definitions.
• Some AutoCAD-specific data cannot be translated completely. For example, features such as dynamic blocks, can be represented visually but not behaviorally.
• Nested references are not merged into the host DGN file when exporting to V7 DGN. The nested reference is not displayed in the host DGN file but the reference chain still exists.
• AEC objects are not exported to DGN. Use the EXPORTTOAUTOCAD command to convert the AEC objects to base AutoCAD objects before exporting to DGN.
• AutoCAD does not export linetype definitions to DGN files. If the exported DGN file contains references to linetype definitions, the linetypes might not display correctly in MicroStation.

See the DGNEXPORT Conversion Table for specific details about the scope of exporting DWG objects and other data to DGN files.

Note: Do not export drawings that include V8 DGN underlays to a V7 DGN format file. V8 DGN references cannot display in a V7 DGN file. The V8 DGN file format is not a valid design file for the resulting V7 DGN file.

Recommendations

To optimize the data transfer to the MicroStation DGN file format, consider the following recommendations:

• Minimize the use of custom objects and other data unique to AutoCAD-based products.
• Use simple linetypes as much as possible.
• Use simple hatches and hatch styles.
• Use simple gradients and gradient styles.
• Use simple dimension styles if possible.
• Use TrueType text fonts rather than SHX text fonts.
• Work primarily in one format, DWG or DGN, rather than switching back and forth

Conversion Units

When exporting, match the DWG file's drawing units either to the master units or to the sub units of the DGN seed file. A DGN seed file is similar to a drawing template (DWT) file in AutoCAD. It contains default settings and attributes such as working units, for the DGN file.

For example, assume that you are exporting a DWG file that was created in inches. The DGN seed file you selected has its master units set to feet and sub units set to inches. While exporting, in the Export Settings dialog box, select sub units in the Specify Seed File section. This matches the inches used in the DWG file with the inches specified in the DGN seed file.

Note: Some programs that work with DGN files do not support extended characters for file names. As such, do not use accented or Asian characters in file names when using DGNEXPORT.