Abstract: A machine is especially adapted for coating a profile insert and can be distinguished by the fact that it consists of several extruder screws (1, 2, 3) incorporated into a single block (4), each fed from a hopper opening, through a corresponding orifice (1', 2', 3'), into a union head (5) having a channel (6, 7, 8) for each material being extruded and hollowed out axially for an insert to pass through, this union head (5) feeding, via a distributor ring (9) perforated and grooved concentrically according to the channels in this head, an extrusion chamber (10) with controlled streams, carrying at its exit an extrusion head (11) with a reserved passage for the insert, the head consisting of a frustoconical liner (12) housing, between its entry and its exit, an externally ribbed diffuser (13), in which each groove between two ribs corresponds to an orifice of the extrusion chamber (10), an externally ribbed and grooved frustoconical core (13a) such that its ribs and grooves corresponds to those of the diffuser (