I am not sure I understand.
The 2D is derived from the 3D.
What are you changing in the 2D?
You can Retrieve Dimensions and use the Model dimensions in the 2D to edit the 3D.
Better attach an example (your 2D and 3D) to illustrate exactly what you are trying to do.
I would seldom copy and paste from AutoCAD to Inventor (especially for beginners) as the AutoCAD was frequently not done correclty.
Did you dimension and constrain the 2D sketch in Inventor after pasting?
Create associative 2D dwg or idw in Inventor from the ipt.
Forget the obsolete 2D AutoCAD moving forward.
Attach your files here if you can't figure it out.
Hi Oakcutter,
You can create a link to the original *.dwg file by going to the Manage tab > Insert panel > Insert Object button. This tool allows you to place a 3rd Party node in the browser that will contain a link to your original file. It will not be an associative reference though. Meaning that if you were to delete some of the geometry in AutoCAD, it will not update the Inventor file. But it will allow you to document the source drawing in your Inventor file.
I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com