Sometimes 3D is overkill and 2D CAD is needed.  Here are some examples of 2D CAD work.

PD-2Card PD-2_A-frame_1-6x2_E_Page_1 PD-2_A-frame_1-6x2_E_Page_2PD1-DynonDrive04-720-480IMG_3060PD-2_Ramp10