If you want to make a 3d printer from electronic waste and recycled parts from junk 2d printer, you will find this software tools very useful. They generate model of a 3d printer with FreeCAD plugin based on the parts you have. It should help you enormously to design your own custom 3d printer from available parts.
Example of the generated 3d printer:
The projects are still in development and I don't have enough knowledge to test it out but it looks very promising. There seems to be a link between those two projects but I'm not sure what it is.
You can try the web applications where you can input all of the parts and their specifications and get the output FreeCAD design:
source code is available at: https://github.com/Maaphoo/Retr3d
Here is the part of the web app menu with ton of options for various parts:
Github.io page (currently not working):
Source with comments discussion:
Let me know if you have any experiences with it!