Basics of Sheet Metal Design

Sheet Metal: Involves cutting and forming operations performed on relatively thin sheets of metal

  • Applications: High commercial importance, automobile and truck bodies, airplanes, railway cars, appliances, furniture, office equipment
    o Many of internal components are also made of sheet or plate stock
  • Sheet Thickness: 1/64 in. to ¼ in.
    o Thickness greater then ¼ inch is considered a plate
  • Sheet is made from metalworking flat rolling process
  • Most common used sheet metal is low carbon
  • Advantages: Characterized by high strength, good dimensional accuracy, good surface finish, relatively low cost
    o Suitable for economical mass-productions
  • Usually performed at room temperature (cold working)
  1. Stamping press: Machine where most sheet-metal operations are performed
  2. Punch-and-die: Tooling that performs sheet metalwork (stamping die)
  3. Stampings: Sheet-metal products

Three Major Types of Sheet-Metal Processes:

  1. Cutting
    a. Shearing: Cutting operation along a straight line between two cutting edges
    b. Blanking: Cutting operation along closed outline in single step to produce desired part
    c. Punching: Cutting operation along closed outline where remaining stock is the part
  2. Bending: Straining of metal around a straight axis to produce plastic deformation
    a. Produces little or no change in thickness of sheet metal

    Other Bending/Forming Operations
  • Flanging: Straight, stretch, shrink
  • Hemming: Bending the edge of the sheet over on itself in more than one bending step
    o Improves stiffness and improves appearance
  • Seaming: Similar to hemming but where two sheet-metal edges are assembled
  • Curling: Forms the edges of the part into a roll or curl
    o Done for safety, strength, and aesthetics
  1. Drawing: Sheet-metal forming process used to make cup-shaped, box-shaped, or other complex-curved and concave parts
    a. Common parts: beverage cans, ammunition shells, sinks, cooking pots, automobile body panels
  • If shape change required by the part design is too severe, complete forming of part may require more than one drawing step
    o Additional steps called redrawing
  • Blank holder purpose: Prevents wrinkling of the flange while cup is drawn
    o Wrinkling, tearing, earing, surface scratches