Method for producing a lightweight gear by double overmoulding

A method for manufacturing a toothed wheel, said method wherein a carrier core realization step (a), during which a carrier core is made of a first polymer material, said carrier core including a hub with a main axis (XX′), as well as a collar which extends substantially radially from said hub, away from the main axis (XX′), up to a peripheral flanged edge said collar being delimited axially by a surface called <<upper>> surface orientated on the side axially opposite to the flanged edge and by a surface called <<lower>> surface axially orientated on the side of the flanged edge said method then comprising a coating step (b) during which is carried out by overmolding on the carrier core in a second polymer material, a permanent coating layer which remains permanently on the completed toothed wheel said coating layer comprising in one piece, on the one hand, a frontal layer which covers the upper surface of the collar as an axial over-thickness of said collar and, on the other hand, a lateral layer which axially extends said frontal layer by covering the radially outer surface of the flanged edge as a radial over-thickness of said flanged edge, so that said lateral layer forms a wheel rim in the radial thickness of which the meshing teeth of the wheel are realized, the method being wherein, during the carrier core realization step (a), forming channeling grooves in the carrier core, wherein the channeling grooves extend substantially radially on the upper surface of the collar, up to the flanged edge, and further extend axially, in forming an angle, along said flanged edge on the radially outer surface of said flanged edge.