Method for producing an at least single-walled tube body from thermoplastic material in an installation, in which at least one tubular preform is discharged from the nozzle head of an extrusion device, the preform is guided vertically downwards, the preform is expanded to a predetermined extent in the transverse direction and to a predetermined shape in an expansion operation by an expanding core arranged centrally in relation to the nozzle head, wherein the preform remains open at the top and bottom, in which, to produce the at least single-walled tube body, which is provided with a corrugated profile or cup-shaped profile, the expanding core has expanding elements (24, 26) provided with a corrugated profile or cup-shaped profile, wherein, by applying a vacuum to the expanding elements, the hot preform takes on the corrugated profile or the cup-shaped profile of the expanding elements (24, 26), and/or in which, to produce the at least single-walled tube body, an at least two-part hollow mould arranged around the tubular preform is used, wherein the hollow mould has a corrugated profile or a cup-shaped profile, wherein, during the expansion by the expanding device, the preform is pressed against the corrugated profile or the cup-shaped profile of the hollow mould and, as a result of applying a vacuum to the hollow mould and/or compressed air to the expanding core, the preform takes on the shape of the corrugated profile or cup-shaped profile, after the cooling of the at least one preform (14, 14a, 14b), the expanding core is moved into a non-expanded state, and in which, after this, the at least single-walled tube body is removed from the installation. in which at least one tubular preform is discharged from the nozzle head of an extrusion device, the preform is guided vertically downwards, the preform is expanded to a predetermined extent in the transverse direction and to a predetermined shape in an expansion operation by an expanding core arranged centrally in relation to the nozzle head, wherein the preform remains open at the top and bottom, in which, to produce the at least single-walled tube body, which is provided with a corrugated profile or cup-shaped profile, the expanding core has expanding elements (24, 26) provided with a corrugated profile or cup-shaped profile, wherein, by applying a vacuum to the expanding elements, the hot preform takes on the corrugated profile or the cup-shaped profile of the expanding elements (24, 26), and/or in which, to produce the at least single-walled tube body, an at least two-part hollow mould arranged around the tubular preform is used, wherein the hollow mould has a corrugated profile or a cup-shaped profile, wherein, during the expansion by the expanding device, the preform is pressed against the corrugated profile or the cup-shaped profile of the hollow mould and, as a result of applying a vacuum to the hollow mould and/or compressed air to the expanding core, the preform takes on the shape of the corrugated profile or cup-shaped profile, after the cooling of the at least one preform (14, 14a, 14b), the expanding core is moved into a non-expanded state, and in which, after this, the at least single-walled tube body is removed from the installation.