Abstract: To achieve the hot deformation of a work piece (2), for example by folding a piece of plastics material, the method includes exerting on the work piece (2), in the zone (2a) to be deformed, a controlled deforming pressure (P1) and, during at least the initial stage of the application of this pressure, heating the work piece in a controlled manner, at least in the zone (2a) to be deformed, whereby, under the combined effect of the pressure and the heat, the work piece is deformed into the desired final state when it has reached a temperature in relation to the mechanical deformation stress to which it is subjected.