Tuesday, July 1, 2008

AutoCAD linked into Revit

A list of issues in linking AutoCAD files into Revit

  • Not all AutoCAD line types can import into Revit – eg Insulation – Customised AutoCAD line types with symbols and text.
  • Arrows on leaders and dimensions some times do not display properly in Revit. One solution is to ensure all leader arrow head are a block with-in the dimension leader.
  • Linked AutoCAD items can not be used to dimension off as if the link path becomes broken, the dimension, will be deleted.
  • When doing milestone archives in Revit (for future Revit version ease of compatibility) all AutoCAD linked files need to be removed. Thus the intent of having them in there in the first place is lost.
  • Each AutoCAD files should only be linked into one view, or all the views. In the event it is only in one view, when it is turned off in that view it can be near impossible to find which view it has been linked into. In the event you link it into every view, you then have to manually turn it off in every view. Never copy a linked file within Revit. When the original one is removed the copied link will also be removed.
  • When creating dwg files for Revit Views, you need to create a separate detail AutoCAD file for every view. This is required for proper cross referencing. General AutoCAD users won’t be aware of this so you will need to ensure you inform them.
  • When creating dwg files to be linked into Revit every element must be drawn by layer. It is also important that dwg files linked into Revit Drafting views should not contain any additional drawings or old details out to the side, as drafting views can not be cropped. Really it is good practice to remove these kinds of old details to the side from all AutoCAD linked files.
  • Avoid linking dwg files that have xrefs within them. Other that an uncertainty of if they will view properly, in the event they become corrupt, you might have difficulties in opening your Revit file.
  • Currently there are some know bugs with exporting views/sheet that have linked AutoCAD files. The link does not end up exporting. This seems to happen on large links (area), and resolutions include turning off the crop region of the view.
  • Excessive AutoCAD linked files can slow down opening time of the Revit project file.
  • AutoCAD dynamic blocks using visibility setting in links may become distorted once imported into Revit.
  • Some AutoCAD hatches will not appear correctly when imported or linked into Revit. The only solution is to explode them in AutoCAD or use a different hatch.
  • AutoCAD files with shx fonts may not appear correctly when linked into Revit. The solution is to map your .shx fonts in AutoCAD to Revit TrueType fonts by editing the file "shxfontmap.txt" (which you can find in the "Data" Folder of your Revit Architecture installation directory, - C:\Program Files\Revit Architecture 2008\Data). To edit this file, first type in your Autocad .shx font you are using in your drawing and give a space/tab and type in the TrueType font you want to use in Revit.
  • AutoCAD linked files containing AutoCAD text symbol shortcuts (this includes underlines and degree symbols) will not appear correctly in the Revit view.
  • Large AutoCAD linked files into Revit can generate the following Display Error: “An error has occurred while drawing the contents of this window. This window shall be closed”. The result is the file crashes.

Quite a long list isn’t it! Yet the Autodesk sales person how tries to sell you Revit will tell you AutoCAD is 100% compatible with Revit. To be really honest, there are very few software packages out there that are 100% compatible in regard to file transfer. From the above, most of the issues comes up with shot falls in AutoCAD and how it codes it’s file. The upside it that Autodesk did learn it’s lesson that backward compatible files, means bad programme decisions in the past are near impossible to correct. So the question really is; how should you use dwg files with Revit?

General Recommendation

Links are great for reference /coordination files where you won’t be printing them out as part of your drawing set. When you have finished your reference / coordination (ie with the structural engineer or mechanical / electrical engineer) remove the linked file.

Avoid using dwg linked files where the dwg is going to be updated throughout the current stage of the project. You can just never guarantee it will print out correctly every time. The idea of doing 2d work in AutoCAD and linking it into Revit is a copout to learning Revit and from above is plagued with possible problems. 2D detailing in Revit is easy and when you get your head around it quicker than AutoCAD.

Importing a dwg is not the end of the world. Personally, I recommend it for site survey plans. Ensure the dwg file is fully cleaned up before importing (purge, logical origin, remove hatch patterns, change all text to Arial, remove leaders and dimension, remove un-necessary lines, flatten, minimise layers, ensure all the lines are on the correct layers ect). The thing is when you import it and explode it, if items don’t display correctly, you can fix then and there, and be 100% confident it will print out and reference correctly in the future. These new imported exploded items now become Revit lines, and thus can be edited and updated.


joseph said...

Very Helpful Blog post, i do however not recommend exploding DWGs within Revit, even the cleanest DWG can cause you issues once exploded, particularly with blocks.

Line said...

HI there Brian, thanks for a really nice blog....it is good read some of the issues you have come across. I cant stop guessing which ones are from 567. Anyway I tend to approach my dwg different in detail (2d lines like a mullion) which I always explode and to siteplans(not survey though) which i do not explode. I agree that you need the setout of the project exploded. Here I use the site boundary tool so that is kind of a redraw of the survey. I was wondering if you have room for questions too? Line

Brian Renehan said...

Thanks Line.
Please feel free to ask questions. The above post is now a year old and some of it is out of date. I also might do somethings a little different.
So much of what we do, depends on the project. its current stage and the desired outcome requirements.