First I plan the layout of the axles and major gears (seen here side view) to try and place the cams in the correct position. I have opted for a skeleton frame so the mechanism is more visible and the subject is working amongst the mechanism. This keeps the height of the piece down and I think also make it more interesting.
The cog gears are generated in the gear design software from http://woodgears.ca and then adapted in Openscad. The geneva wheel is designed in openscad from a design written by Jesse Donaldson and available on Thingiverse. It has been adapted in openscad, an open source 3D design programme, and then exported into Vectric VCarve Pro where it has been adapted for woodwork and combined with the large cog for cutting as one piece. I have always cut these with a bandsaw/scrollsaw but this time I will use a CNC router for accuracy. The mechanism will be cut from 12mm birch ply which is dimensionally stable and allows tighter tolerances.