Extruder with a shaping device

The invention describes an extrusion system (1) with a shaping device (3), which has at least one calibrating device (9) comprising in particular a plurality of calibrating tools disposed in succession in the extrusion direction. The calibrating device (9) and/or the calibrating tools (24,31 to 33) are provided with cooling ducts (49) for passage of a heat treatment agent (50). The shaping device (3) has mould surfaces for application against an article (6) to be passed through. Furthermore, at least between an extrusion tool (8) of the shaping device (3) and the immediately succeeding calibrating tool in the extrusion direction and/or between the first calibrating tool (24) and at least one further calibrating tool (31,32,33), a seal device is disposed closing off the article (6) to be passed through in the region of its outer surfaces (48) from the environmental pressure, in order to form a cavity (38 to 41).