How do you convert 3d drawing to 2d in autocad?

choose the view you want and type flatshot in command  tick off obsured line  show click create then  type0,0,0

a block will be created automatically insert it  where ever you wish to apply 

if i want 2d plan i select top view and if i want elevelations i will select right or left view .

1. Open the drawing file.
2. Click on the Layout 1 tab to make it current.
3. Delete the existing viewport. (You can eliminate the need for this step in future drawings by deleting it from your template file.)
4. Start the ViewBase command. You’ll find it on the Ribbon menu > Layout tab > Create View panel > Base button. A layout tab has to be current for the Layout tab to show. A couple of paragraphs back, I bragged that I could create the 2D drawing views of our sample part in under a minute. Okay, start the clock!
5. Having started the ViewBase command, click on From Model Space in the drop-down menu that appears. One Mississippi …
6. AutoCAD asks for a view location. Click approximately in the center of the lower-left quadrant of the drawing, then click eXit in the context menu or press Enter. … two Mississippi …
7. AutoCAD continues asking for view locations. Click above the first view, then to the right of the first view, then approximately in the center of the upper-right quadrant of the layout, then press Enter.

USE THE LAYOUT AND GET THE MORE VIEW FROM 3D OBJECT.

just simply import your drawing to autocad and explode.

there is a very convenient way to do that. you can plot it by a dxb plotter which converts your drawing to a 2d lines according to how you are viewing your 3d

If it is your first time to do so, then you need to install the DXB printer (you do that the first time only). To do so, go to plotter manager, and double click on add plotter, a window will appear, you start clicking next till a menu of different kinds of plotter comes, choose DXB plotter and then continue.

After installing the plotter, press ctrl+p, the plot window will appear. Choose your DXB plotter and fix the other printing option as you prefer. after you click on plot, a window will appear asking you to chose the location of the file. A .dxb file will be saved.

Simply drag the .dxb file and drop it in an empty autocad file, and here you go, your 2D drawing comes out.