Why a clean CAD file is important?

Posted on Posted in Workflow

I started to write this post a couple of weeks ago, but with the recent rush it was put on hold. And the timing was right, since couple of my clients sent me a CAD on which I spent many hours cleaning. Results: the estimates I provided was no longer valid and for a good reason.

What do I look in a 3D CAD file before starting my rendering?

Once I received a CAD file from my clients I open it up to see how it looks.  For some renderings, it is required to have a floor plan converted to 3D as well, naturally, the furniture is on a separate layer. In any case, I change my views from top or ISO views to side views to see if all the 3D blocks or on 0 Z axis. Simply put: Are all my 3D blocks on the floor? or are some of them floating?

Floating Furniture
Some chairs are above the ground and some are under.

This usually happens when the 2D symbols are converted to 3D.

A few good practices before sending your CAD files for 3D rendering

  • Copy the 2D blocks and paste them in a new document and then convert them in 3D.
  • Also if you convert many symbols and many typical, it is possible that some files won’t get converted or end up with a different Z axis. So the rule for my workflow is: one typical one CAD file.
  • Next step is to reduce the file size and the number of common block like identical chairs or monitor supports etc.
    • I delete all but one of each chairs and noting where they go. For example: if the typical is a private office, it usually has a task/executive chair and couple of guest chairs.  I keep the task chair and delete all but one guest chair.
  • I do the same for monitor supports.
    • Monitor supports can be specially an issue as they are usually a solid model or come from different manufacturer which maybe about 100 kb to 500 kb each. So if your scene contains a few dozen of them, it all adds up.
  • I also delete any CPU blocks or accessories like books and binder added by the designer.
  • Once the clean up is done and I’m happy with it, I use the PURGE command to clean up all the unnecessary blocks, layers etc. This command has been part of AutoCAD for as long as I remember. I don’t even know if there is an icon for it, I always type the command.


  • When using Purge command, make sure you select “Purge nested items” and deselect “Confirm each item to be purged”, as this last one will ask you for each purge, and in some cases it may require many clicks on OK button.
  • Also, make sure you select “Automatically purge orphaned data”
  • I always suggest using eTranmit before sending me your CAD. This will ensure that I have all the Xref files as well as any special blocks you may use in your CAD file. And besides, it makes a nice Zip file and prepare it for your email.


And that’s all the manipulation I do to my CAD files. This whole process should take about one to two minutes per typical. If however there are floating objects, then the manipulation goes beyond what I described here.

I hope this was helpful. Please do not hesitate to send in your comments and suggestions on how you optimize your CAD files.

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