When I posed the question about creating a 3d model of a "complex" ramp ,I wasn't very specific about its' outline .The shape of the ramp is what makes my work difficult. It looks like an "s" created by 2 inverse spirals. The problem appears since the ramp follows a curly path.
I first created the perimeter of the ramp's shape(polyline), then extruded the polyline. After having divided the solid in many segments in an attempt to reach a level of accuracy that would be satisfactory , I started creating slices all over the 3d solid following the reclination of the ramp.The attempt seems too complex and takes quite a lot of time to achieve. In addition, the result isn't good enough,smooth enough. since when rendering the model, edges appear along the path.