The interest into gear noise problems is increased remarkably in the last ten years. Variable mesh stiffness, impacts and backlash affect the transmission error, main source of not desiderate noise. The control of gear geometry, as well as the influence of contact ratio and loads, plays a key role in this effort. In the present paper a new methodology for the realization of an integrated CAD-FEM bidimensional model for spur gears is proposed. This CAD-FEM tool provides exact gear geometry, relative positioning and the automatic mesh for a wide family of spur gears. The code generates the gear profiles based on the parameters describing the cutting tool. Particular attention is paid on simulating the enveloping process when protuberance and semi topping exist. The shaving manufacturing process is also taken into account. A parametric routine is used to automatically generate the mesh according to the teeth profiles geometry. Finally some case study are presented to validate the model and demonstrate how static analysis can be performed accurately in a very simple way