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Sheet metal cutting and forming operations

Short answer

Blanking: cut-out piece is product, die opening sized; piercing: cut-out is scrap, punch sized. Shearing cuts along straight line with blades. Bending forms sheet along axis, overbend for springback. Roling uses three rolls to curve sheet into cylinders. Punching removes slug to create hole (same as piercing).

Differentiate between blanking and piercing. Explain shearing, bending, rolling and punching operations of sheet metal work with sketches.

Sheet metal is generally 0.4 to 6 mm thick; its operations are of the cutting and forming types.

Blanking and piercing

BlankingPiercing (punching)
Cutting the outline of a piece from a sheetCutting holes in a sheet
The cut-out piece is the productThe cut-out slug is scrap
Die opening is the size of the blankPunch size is the hole size
Clearance is applied to the punchClearance is applied to the die
Example: coin, outside of a washerExample: washer hole

Shearing

Cutting a sheet along a straight line between two blades. A guillotine shear has a fixed lower blade and a moving upper blade, inclined at a small rake angle to lower the force. Hand shears (snips) cut thin sheets.

   upper blade \
   ============ \___ sheet
   lower blade ______|

Bending

Forming a sheet along a straight axis by stressing it beyond its yield point. Air bending, V-bending and wiping (edge) bending are done in press brakes and dies. Springback occurs, so a slight over-bend is given. The minimum bend radius depends on the ductility of the material (about 1 to 2 times the thickness).

          punch
            |
            v
    \               /
     \   sheet     /    sheet bent to a V
      \___________/
    [   V-shaped die   ]

Rolling

A sheet is passed through three rolls (pyramid or initial pinch type) to form cylinders and curved shapes. Moving the top roll changes the curvature.

            ( O )          top roll (adjustable)
    sheet ~~~~~~~~~~~~~
       ( O )     ( O )     two bottom rolls

Punching

A punch and die pair removes a slug to form a hole; it is used for holes, slots and notches. CNC turret presses punch many shapes.

           | punch |
           |_______|
   ========|       |========  sheet
   [  die  ]  slug  [  die  ]
               v

✓ Answer checked by Claude Opus 5.5 (high effort)

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