When inserting a DXF file as a background in the Standalone version, there is a long delay before the background appears.
How can performance be improved for load time of large CAD file background layers?
In some cases if the DXF file is very large with a large amount of complex linework, it can take a very long time to load. There are a number of other factors that influence this.
First, try saving to a different format from the native CAD application. For example if you're using MicroStation, save to a DGN and try adding that as a background (DGNs are supported in the latest versions). You can also try saving to a different DXF version (such as 2013, 2010, R12, etc)
Next, if possible, use the AutoCAD or MicroStation integrated platform. AutoCAD integration is available in SewerGEMS, WaterGEMS and HAMMER and an extra cost for your license for WaterCAD, SewerCAD and StormCAD. Version compatibility information cam be found here. This will allow you to load the DXF in the native CAD environment while working on your model.
Another option is to try reducing the complexity of the CAD file. This depends on many factors, but a list of possible operations as as follows:
If this still does not help and you have access to an application such as ArcGIS, try converting to to Shapefile format, which ModelBuilder also supports. See this article.
Note that further improvements to DXF background loading performance may be investigated for a future release - reference #818847
Attaching a DWG or DXF as a background
How to increase model performance / reduce run time (recommended minimum system requirements)