Lancing is a piercing operation in which the workpiece is sheared and bent with one strike of the Die. A key part of this process is that there is not reduction of material, only a modification in its geometry. This operation is used to make tabs, vents, and louvers.
The cut made in lancing is not a closed cut, like in perforation even though a similar machine is used, but a side is left connected to be bent sharply or in more of a rounded manner.
Lancing can be used to make partial contours and free up material for other operations further down the production line. Along with these reasons lancing is also used to make tabs (where the material is bent at a 90 degree angle to the material), vents (where the bend is around 45 degrees), and louvers (where the piece is rounded or cupped).
Normally lancing is done on a mechanical press, lancing requires the use of punches and Dies to be used. The different punches and Dies determine the shape and angle (or curvature) of the newly made section of the material. The Dies and punches are needed to be made of tool steel to withstand the repetitious nature of the procedure.