A Rogowski coil is used to measure the current in a wire through the center of the coil. See for details for example: https://en.wikipedia.org/wiki/Rogowski_coil The FreeCad script generates the body of a Rogowski coil with specified dimensions and windings etc. The gap in of the coil makes it possible to easily slide the coil over a current carrying wire (shown in gray on the first figure in the gallery).. The windings on the coil are guided by small channels and there are two holes in the body of the coil to feed the incoming and outgoing leads. The wire at the end of the coil can be guided back to the beginning using the channel in the middle of the ring. An alternative design for a Rogowski coil can be found at: http://www.thingiverse.com/thing:283430 The design in the attached file: rigowki.stl was made with the attached FreeCAD script. In the script parameters such as inner and outer radius and height and the number of windings can be modified. The shown Rogowski coil was made on a XYZ da Vinci jr with 0.2mm layer thickness sliced with XYZware with the settings as shown in the figure.