Get that CAD Monkey Off Your Back

Cad_Tools We’ve all known for a while now that we can open CAD data, AutoCAD’s dwg and dxf formats and Microstations dgn format, and most of us have probably at least looked at Conversion Tools and noticed the ‘To CAD’ toolbox but how many of you have gone all the way? If you are curious and want to streamline the process it could be time to read on.

Now draftees aren’t as different as they seem, they’re particular about accuracy and they love layers or levels depending on your preferences. And don’t we all.

In the past you may have used the ‘Export To CAD‘ tool and sent them on their merry way. They have then had to go back and work on that outputted cad file making changes to suit their standards. Now we can actually be much kinder than that with very little effort.

Step one is to get an empty cad drawing from our friendly draftee that has all the layers, blocks and cad entities already in it. All they need to do is give you one of their templates. This is what we call a seed file or CAD template and will contain specific settings and other native base data. A seed file is essential for creating dgn files but optional for creating dwg/dxf files.

Step two, key named fields. This is often only mentioned in hushed tones perhaps only because once they learn we can do it anything less will no longer be accepted. So what are key named fields? Key named fields are specific fields that can control the drawing, this means the line types, colours, geometry, whether the layer is frozen or not and even inserting blocks/cells for points. You can add these CAD fields as attributes in the input feature classes using the Add Field tool or add multiple fields at one time by functional category using the ‘Add CAD‘ fields tool.

Step three is to populate these new fields. For most it will mean the line types or the block/cell names. This can be done using the field calculator. These will be the fields that the ‘Export To CAD’ tool will use when the drawing file is created.

Finally we can run the ‘Export To CAD’ tool and with this we get a few options. These options include what layers we want to export. CAD works with layers much like ArcMap – the only differenece is that the layers are in the CAD file; not referenced to the layers as we are used to. So we add only the layers we want to display in the drawing file.

Next you’ll need to know what version our friendly draftee is using, they are very particular about this and they need to be because we can currently export version 2012 for AutoCad or a V8 dgn for Microstation. This is fine if they are using these releases or a more current one but if they are using an older version they will not be able to open the file.

The next three settings are purely optional. The ‘Ignore Paths in Tables’ allows you to split a drawing file up in separate drawings for each entity. This is set to ignore by default. You also have the option of appending your data to an existing drawing instead of creating a new one. But the last optional setting is the use of a seed file (required for Microstation). This is that template drawing that you asked for earlier that will make everyone in the room happy. This way you will not have to re-jig the exported drawing file later on to  make sure everything is in its appropriate layers and blocks/cells are used where necessary.

Now all these steps can be rolled into one model, so if you’re a part of an organisation where these requests are frequent you can really make this a simple minimal click process and our CAD monkeys can get on with what they do best.


Next time we’ll look at ways to bring in drawings that have arbitrary spatial references or are drawn in millimetres and put them in real world locations.

Kym J

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