复杂的曲面如何生成实体(增厚功能不起作用时）？

当需要把工业设计出来的产品外形曲面变成有厚度的实体时，最基本最笨的方法是什么？(增厚功能不起作用时）？

1)First step:
Offest the outline line(value=the plastic thickness),and create the another face according to the former mothed.
2)Second step:
  Rebuild the another face between the face 1 edge and the face 2 edge
3)Third step:
and then sew the three faces