BIM Software Tips: Preparing to Import CAD Drawings into Revit
1) Organize CAD Graphics Thoroughly
Before importing, make sure the CAD graphics are well-organized. Avoid any stray edges or corners, as well as fragmented elements. These fragments can cause issues during import and may negatively affect layout and printing in Revit more than they do in CAD.
2) Understand the Methods for Importing CAD Graphics
a. Paper Space Layout Method:
Draw your graphics in model space at a 1:100 scale. Set the size of symbols like text and dimensions according to the layout’s scale. Then, adjust the layout viewport scale in paper space to generate the final image. (This is the method often used when exporting CAD drawings from Revit.)
b. Scale Factor Method:
Draw in model space at a 1:100 scale, then zoom in or out according to the desired drawing scale. When adding dimensions, adjust the scale factor of the annotation style’s main unit to match this scale. The final image is created within model space.
c. Combined Method:
Draw using method (a), convert the shapes into blocks, then scale the blocks proportionally, and finally create the image in model space. This approach merges the advantages of both methods (a) and (b).
For example, when importing a CAD drawing into a Revit drawing view, you should set the drawing view’s scale either immediately after importing the CAD file or before reviewing it. The key difference between setting the scale before import and setting it after decomposing the drawing is the size of the imported text. Setting the drawing view scale before importing ensures that text sizes are correct. If no changes are made to the scale or graphic elements, the CAD graphics can remain unmodified.
In summary, regardless of which method you choose, the CAD graphics must be drawn meticulously. If you haven’t fully understood the structure of the CAD drawing you plan to import, postpone the import. Avoid using CAD files that are disorganized or messy, as this will result in more time spent adjusting them within Revit.
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