Method and apparatus for axially shaping a tube

An apparatus for axially shaping a tube (200), comprising

• a clamping device (140) for clamping the tube (200), such that a free portion (320) remains;
• a shaping device (150) axially aligned with the clamping device (140) and having an axially displaceable annular die (120) and a mandrel (110) coaxially guided within the annular die (120),
• wherein the annular die (120) and the mandrel each have a conical axially extending transition portion (110-I, 110-II, 120-I, 120-II),
• wherein the annular die (120) and the mandrel (110) in their juxtaposition span an annular gap for passing through and shaping the wall of the tube (200);
• and
• a controller (152) allocated to the shaping device (150) for moving the annular die (120) and the mandrel (110) independently of each other along the free portion of the tube (200) for shaping the tube (200) in a pushing direction (S) and a pulling direction (Z),
• wherein the controller (152) is configured to perform the following steps:
• pushing the annular die (120) in a pushing direction (S) towards the clamping device (140) over the free portion (210) of the tube (200) while the mandrel (110) leads the annular die (120) in the pushing direction and thereby reducing an original outside diameter of the tube (200);
• upon reaching an end position (E), reversing the direction of movement of the annular die (120) and the mandrel (110) from the pushing direction (S) to an opposite pulling direction (Z);
• moving, in a first setting step, the annular die (120) and mandrel (110) in relation to one another to a first preset annular-gap setting;
• moving, in a first shaping step, the annular die (120) and mandrel (110) in the pulling direction (Z) over a first partial portion (T1) of the free tube portion (210), while maintaining the first preset annular-gap setting;
• moving, in a subsequent second setting step, the annular die (120) and mandrel (110) in relation to one another to a negative annular-gap setting, in which the conical transition portions (110-I, 120-I) of the annular die (120) and the mandrel (110) taper towards a free end of the tube (200) and span the annular gap;
• and
• moving, in a second shaping step, the annular die (120) and mandrel (110) in the pulling direction (Z) over a second partial portion (T2) of the free tube portion (210), while maintaining the second preset annular-gap setting, thereby causing an outer diameter of the tube in the second partial portion T2) to be greater than an outer diameter of the tube in the first partial portion (T1).