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    by Dennis Collin

    DC_ACAD_DGN_01a.jpg

    I was recently asked whether AutoCAD could work with Bentley’s MicroStation DGN files, either opening them directly or being able to use them as reference files. The answer is yes to both functions and this has been available for a number of years.

    DC_ACAD_DGN_02.png

    Fig. DGN is one of the many formats AutoCAD can access.

    To open a DGN (or Design file) choose open and select the DGN format.

    The import converts DGN objects and properties to DWG objects and properties without any issues. For example, levels in MicroStation translate directly to AutoCAD layers. However, DGN objects and properties that have no direct correlation to DWG objects and properties may not translate completely.

    Some issues might arise as a result including:

    • Data with built-in features or variations are visually approximated. For example, text and dimensions with specialised formatting and colour definitions might display differently.
    • Entities in the DGN file that have a colour property set for a symbol lose the symbol colour when imported as a block.
    • Linetypes associated with multi-lines do not display.
    • Entities with DGN line styles in non-uniformly scaled blocks may look different to how they appear in MicroStation.
    • Line style modifier settings of an element in the DGN file are lost when exporting them from AutoCAD back to MicroStation.
    • The Closed property of a DGN polygon or closed polyline changes to No during the import process.

    When importing a DGN file, check that the DWG file's drawing units match either the master units or sub-units of the DGN file. For example, assume that you are importing a DGN file with master units set to metres, and sub-units set to millimetres. You can set the DWG file's drawing units to metres. When importing the DGN file, in the Import DGN Settings dialog box, specify master units as the conversion unit.

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    AutoCAD’s reference attach supports DGN formats as well, simply select the DGN extension and browse to the desired file.

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    AutoCAD can also export to DGN format as well, although certain elements may not translate as expected. It may be worth doing a visual check before issuing a data, or let the recipient import the DWG file within a MicroStation application instead.