Four copies of this part together make an object, whose surface is called Roman or Steiner surface (see figure). For more information see: http://en.wikipedia.org/wiki/Roman_surface (Klein's bottle is mentioned under "remix" as it might be of interest as well).The Roman surface also known as Steiner surface can be described by different equations, see: http://en.wikipedia.org/wiki/Roman_surface Maple 18 offers the new feature to export plots outputs as STL files - it was used for creating this object (using the command plot3d and the equations for x,y,z in polar coordinates). with(plottools) p2 := plot3d([cos(u)sin(u)cos(v)^2, sin(u)cos(v)sin(v), cos(u)cos(v)sin(v)], u = (1/2)Pi .. Pi, v = 0Pi .. .5*Pi, grid = [144, 144]) # output size limited to 1 MB, at least in academic version stlp := "............stl" exportplot(stlp, p2) Important hint: If you want to create and print your own objects, the spherical angles should be chosen such that no point is generated twice (e.g. if phi=0..Pi is enough, then it should not be extended to phi=-Pi..Pi). Otherwise no useable .gcode could be created by the 3d printer software.