(1) Positive extrusion: The direction of metal flow during extrusion is the same as the direction of motion of the punch.
(2) Back-squeezing: The direction of metal flow during extrusion is opposite to the direction of motion of the punch.
(3) Co-extrusion: the flow direction of a part of the metal of the blank is the same as the direction of the movement of the punch, and the flow direction of the other part of the metal is opposite to the direction of the movement of the punch.
(4) Radial extrusion: The direction of metal flow during extrusion is perpendicular to the direction of motion of the punch.