Share 'Extrusion along normal vectors?'

Hi everyone! I created a few arcs with different radii in different heights, transformed them into polylines and extruded these with a Unit Z Vector. What I want to do now is to extrude these generated surfaces towards the central point of the arc, but only with a certain extrusion distance. I tried to show what I mean in the third picture. I'm trying to extrude along the normal vector of every s…