Notching in Press Working

Definition

Notching is a specialized metal shearing process in press working used to remove a specific amount of material from the edge or corner of a metal strip, sheet, or blank. Unlike punching, which typically produces holes within the interior of a workpiece, notching focuses on shaping the external profile to prepare the part for subsequent operations like bending or assembly.

Main Content

1. Purpose of Notching

• It is primarily used to remove excess material from the edges of a sheet to avoid interference during bending operations.
• It helps in creating specific shapes or patterns on the outer profile of a workpiece that cannot be achieved by straight shearing alone.

2. Difference Between Notching and Punching

• Punching involves creating a hole or cutout within the boundary of the material, leaving a closed loop of metal surrounding the tool.
• Notching is an open-ended operation; the shearing tool acts on the edge of the material, often removing a segment of the periphery.

3. Tooling Geometry

• The notching punch is usually designed with a specific angle (e.g., 90 degrees for corner notching) to match the required cutout.
• Clearance between the punch and the die is critical to ensure a clean cut and to prevent burrs on the edges of the metal.

       Punch
      /     \
     /       \
    |         |
    |         |
    +---------+
    |         |
[ Workpiece Edge ]
    |         |
  --+---------+--
   Die Opening

(Diagram: Typical setup for a V-notch operation on the edge of a metal sheet)

Working / Process

1. Material Positioning

• The metal sheet or strip is guided into the press, usually against a stop or gauge, to ensure the notch is placed accurately at the desired edge location.
• Proper alignment is essential to maintain the dimensional tolerance of the final part.

2. Shearing Action

• The press ram descends, driving the punch into the workpiece. As the punch enters the die, it shears the metal through the thickness of the sheet.
• The shearing process happens in stages: elastic deformation, plastic deformation, and finally, the actual fracture or separation of the metal slug.

3. Slug Ejection

• Once the metal is sheared, the piece of scrap (called the slug) is pushed through the die opening.
• The workpiece is then moved forward or removed from the press, and the process is repeated for the next piece or next section of the sheet.

Advantages / Applications

• Bending Clearance: Notching removes material that would otherwise wrinkle or overlap when bending a sheet into a box or enclosure.
• Structural Optimization: It reduces the overall weight of a component without significantly compromising its structural integrity.
• Assembly Preparation: It creates notches for tabs, slots, or locking mechanisms that allow two or more pieces of sheet metal to fit together perfectly.

Summary

Notching is a fundamental press working process that involves removing specific shapes from the edges or corners of a workpiece to facilitate bending, assembly, or profile shaping. It differs from punching because it is an edge-based operation. Key terms to remember include "Shearing," which is the cutting action; "Slug," which refers to the scrap material removed; and "Clearance," which defines the gap between the punch and die required for a precise cut.