Shoehorn Your Civil 3D Model into a CAD Standard
How often have you had a last-minute change in scope? Or a tiny little change that went unnoticed until the week before—or even the day before—a submittal? I've been there several times and most often the one little change is the CAD standard that the team should have been following the whole time. This article will help you make a quick and dirty conversion of your drawings to fit another drafting standard.
The first thing you need to do is take a deep breath and look at the project from a high level. How many sheets, files, and references are you dealing with? Look at how these things are related to and/or dependent on each other.
Second, look at a sample of the final deliverable and how the drawings will be checked. If you can get a hold of the reviewer, ask what they are looking for with respect to CAD standards compliance. Oddly enough, the client is not always interested in every detail of the standard. Maybe they don't really care about anything except the report that comes out of their standards checking software on its default settings.
Once you have a grasp of the minimum requirements for the deliverable you can make a plan to get there in the fewest number of steps. Using this method, we made a 500-sheet project comply with a well-known CAD standard in about half a day.
Part 1: Clean Up the Base Files
The biggest time savings comes from cleaning up and simplifying the drawings. Only then should you figure out how to use automation to speed up your work. You don't have to convert every layer in your AutoCAD® Civil 3D model. You may not need most of the objects in the model to show up in the final deliverable.
Pick the layers you need to pull out of the model and leave the rest behind. Even though we had eight miles of corridors and about a thousand acres of surfaces, from a CAD standards compliance point of view there were only a handful of layers that ended up on the plans.
In my example project, the only C3D generated objects we needed to show on the finished plans were:
- Existing and finished grade contours
- Drainage pipe networks
- Profile views
That may seem like a lot of objects, but when you count the layers it's not that much. There are a couple of contour layers, a couple of drainage layers, a centerline layer and a couple of text layers. By the way, all of the profile views, section views, annotations and labels end up on the same text layer according to the CAD standard I was working with. Your mileage may vary, but I suspect that the list of layers you really need to convert is much shorter than you might think.
Notice that assemblies, corridors, feature lines, and grading objects are not on the list at all. One of the sayings my Civil 3D instructor told me early on was, "A surface is a surface is a surface"—which is to say that it doesn't matter how you build the finish surface as long as it comes out correctly. Everything that goes into building that finish surface can be thought of as scratch work. As such, all those layers used to build a corridor will not show up on the final sheets and you do not have to worry about converting these layers.
The final product is what matters; therefore, you should build that finish surface in one drawing and then data reference it out. Then data reference the finish surface into your grading plans, profile sheets, sections, and anything else that needs to show the finish grade.
Part 2: De-Civil 3D Your Drawings
One day we will have to turn in the Civil 3D files for some kind of BIM standards compliance check. But until then you should deliver a clean vanilla AutoCAD .dwg file to ensure maximum compatibility with whatever tool will be used to check your drawings.
Once you have built your list of essential layers, you can export the Civil 3D model to a vanilla AutoCAD drawing using _AecExportToAutoCAD2010 (File --> Export --> Export to Autocad --> 2010 Format) or the AECOBJXPLODE command (Figure 1).
I ended up using AECOBJXPLODE more often than _AecExportToAutoCAD2010 because when an error occurs in AECOBJXPLODE you can click through the error messages and maybe get a workable file at the end. When _AecExportToAutoCAD2010 gets an error, the command aborts and there's no output file to fix.
The next step (Figure 2 and 3) is to do the massive cleanup with PURGE and LAYDEL. It is worth noting that the LAYDEL command was more useful than PURGE here. PURGE will not delete a layer that contains objects, but LAYDEL will delete a layer along with any objects on the layer. This can have unintended consequences and delete objects that need to remain on the plans. When you use LAYDEL you should zoom to the extents of your drawing first and keep an eye out for anything that disappears when you run LAYDEL. In case you do delete something you shouldn't have, you can undo LAYDEL to recover what was lost.
The commands you will use (or script) to clean up your drawings are:
At the end of this process you should have a clean drawing that only includes the layers actually used in the drawing. All Civil 3D objects should now be exploded down to basic AutoCAD objects.
Part 3: Apply CAD Standards
Once the drawing files are pared down to their essential layers, use the CAD Standards checker to make the files conform to the standard. It is important that you have a template file that matches the CAD standards perfectly. Open the template in AutoCAD and save the file to a .dws (Drawing Standards file). This file will be fed into the CAD Standards Checker.
On the Manage tab of the ribbon, click Configure under the CAD Standards panel (Figure 4).
Click on the " + " icon to add a standards file to the checker. You can add multiple standards file in this window and the CAD Standards Checker will check the .dwg against all of the standards files at once. Please note that each .dwg will remember which standards file(s) it is checked against. Therefore if you have to conform to different CAD standards from project to project, you will have to manually change the standards file as you work on each drawing.
Make sure to check the box labeled "Automatically fix non-standard properties." The CAD Standards checker will apply recommended fixes without prompting you to click the Fix button (Figure 5).
You should also disable the standards notification bubble (Figure 6). If the notification is left enabled, the notification bubble will pop up every time you save a drawing that has any non-compliant layers. If you run this standards compliance clean up before you submit CAD files, there will be no reason for you to keep the drawings compliant as you do your day-to-day drafting work.
Now you are ready to run the Checker. Figure 7 shows the CAD Standards Checker when it finds a minor deviation from the Standards file.
Figure 8 shows the CAD Standards Checker when it cannot find a matching entry in the Standards file.
Running the checker is simple and the Fix button was able to correct about half of the minor deviations from the standard that were found. The rest of the fixes involved manually mapping the incorrect layers to the Standards compliant layers.
The second to last step is xref the cleaned up .dwgs into the finished sheets. It is important to do this step on a computer that is isolated from the server where your drawings normally live. When you send your drawings in to be reviewed, those drawings will not be able to reach your server and the xref links will break. AutoCAD's default behavior is to then search the current folder for the xref file. If AutoCAD still doesn't find the xref, it will display the broken xref link in your drawing. You will want to test this before turning in the CAD files to be checked.
Often a CAD standard or client will require xrefs to be bound to the drawings to eliminate this xref problem. If you do bind your xrefs, make sure to use the Insert option to keep the layer names from inheriting the xref's file name. I have seen clients or organizations that want to keep xrefs unbound from the sheets, even if this goes against the CAD standard. So it is best to check first before submitting the CAD files.
Once your drawings have been conformed to the CAD standard, the last step is to make sure they match the hard copy plans.