Why can't I combine a EV3 Motor with a Technic frame in LDD?
I slid the Technic frame over an axle instead of a pin to see how far it would go. As shown in the picture below, it appears as if the part is too big to fit all the way because the rim (shown level with the red line) is too thick.

LDD runs a basic collision detection to ensure that no parts overlap. In real life, certain combinations of parts are impossible without stressing the bricks. 

The combination of EV3 Motor and Technic Frame in real life have a very, very small amount of friction, so it shouldn't be harmful. But LDD has no tolerance for overlapping parts.



You do have several options:


Edit the LXFML file.
This is the most technical soloution. Export the LDD file as a .lxfml file as opposed to the standard .lxf. Using a text editor on your computer (such as notepad) you can directly adjust the co-ordinates of the pieces to overlap. However, If you do move the parts apart, you will need to manually put them back together by editing the file. You can find more about LXFML here.
Different Parts. Use different parts that perform the same function as the Technic beam, or don't include the part at all.
Other Software. You may find it easier to build your model in other LEGO CAD software packages such as lDraw. It should be possible to export your model as it is now and import it into most LEGO CAD applications.