Export to DWG from Revit issues

Even though Autodesk owns both AutoCAD and Revit, it is quite ironic that the export to CAD command does not work properly. There are so many issues outlined even in 2006, and most of them are still resolved.

The most irritating is the one related to the dimensions. When I export a sheet like:

with dimensions and if I choose any option other than the “overrides BYENTITY” in the CAD Export Format dialog box:

It results in out of scale dims like:

Not good.

Page setups are not similar in Revit and AutoCAD. So those don't get transferred too.

AutoCAD has a ‘nice’ printer called ‘None’ which has all the page sizes. Revit should retain the paper size from the title block and use the None printer while exporting sheets. This will not give a ‘printer missing’ error message in AutoCAD (when the DWG file is being opened), but still give the user an option to select an appropriate printer from the user’s network to print to the correct size.

Turn off grids and levels from linked Revit projects

We link a structural revit project into most of our revit projects. We typically develop the grid and after finalizing it, let our engineers maintain it.

We cannot show their grids in our views because, Revit does not allow the linked grid heads/extension to be tweaked. So, we typically copy/monitor the grids. However, when we tweak the grid heads, we see the linked grid head beneath:

One could go into the visibility graphics, and switch off the grids from the linked file on a view by view basis, but exploiting the workset option is more elegant.

Go to File menu > Manage links… and select the structural model and select ‘Reload From…”

and select the same linked structural file. Before pressing ‘open’, select the small arrow next to the ‘open’ button:

and select specify. Then press ‘open’. Revit shows the ‘Linking Worksets…” dialog box.

Select the ‘Shared Levels and grids’ workset and press ‘close’ and then Ok and again Ok. Now the ‘Shared Levels and grids’ workset from the linked file is closed and is NOT visible in any Revit view. Even though the linked grids are not visible, Revit still ‘monitors it!!!

If for some reason you want to see the structural grids, you can repeat the steps above to make them visible.

Blue dots in structural columns

A very simple issue came up the other day. Out of no where, suddenly, all our structural columns in a view started showing a thick blue dot at the center in plan. This ‘thing’ even got printed and was an annoyance.

Revit switches on the blue blob (and the green lines for walls) if the ‘analytical model’ subcategory for these elements are turned on in the visibility graphics. This sub-category does not show up by default in the VG:

However, if we switch on the “Show categories from all disciplines” check box, the sub category shows up:

Turning this sub category off removes these unwanted elements from the view. So far so good. But, how did these ‘analytical model’ elements get turned on in the first place, ‘so’ suddenly?

Accidentally, the visibility of the link was set to use a ‘linked view’, which incidentally had all these analytical model elements turned on!

Export AutoCAD MEP to Revit

Autodesk has a white paper on effective collaboration between Revit (Structure) and AutoCAD MEP which talks about exporting Revit objects to AutoCAD MEP as intelligent entities. If you want to import AutoCAD MEP entities into Revit, the whitepaper recommends to use the “Export to AutoCAD” feature within AutoCAD MEP. No intelligent entities here.

Autodesk has another white paper on exporting Revit elements as ACIS DWG objects, to be imported into AutoCAD MEP which does not work for us, since we want the conversion the other way.

We are examining the pros and cons of bringing in the AutoCAD MEP entities as IFC objects into Revit. The irony is that the MEP consultants typically work on separate DWG files for each floor and each disciplines (M, E and P). This means that we get around 30 IFC files for a 10-floor-project! Hmmm... So here is the best practice we are experimenting with:

1. Create a master file:
1. In AutoCAD MEP create a new DWG.
2. Xref all the floors and discipline DWG files. The project navigator should do this very easily.
3. Save the file, say as, “MEP Project.dwg”
2. Export to IFC for architects using Revit:
1. Open the “MEP Project.dwg”
2. Save as the file as “YEAR MM DD - MEP Project.dwg”
3. Bind and explode all xrefs. Now the DWG should have all MEP elements for all floors and disciplines.
4. Export to IFC.

The best part of creating a master file (“MEP Project.dwg”) is that, this DWG is still linked to all the other DWGs and will automatically get updated. The consultants have to just open this DWG and saveas, bind and explode and export as and when needed.

The Revit does not work 100% perfectly with IFC. However, it should  work fine.

All this is theoretical for the time being. This page will be updated as and when things unfold. Please add your comments if you have a better method.