Sheet Metal Working Techniques

Overview of Sheet Metal Working Techniques

  • Involves various manufacturing operations to create components from sheet metal.

General Applications

  • Common products manufactured:
  • Motor car bodies
  • Truck bodies
  • Pots
  • Airplanes
  • Railway cars
  • Farm and construction equipment
  • Appliances
  • Cutting blades
  • Computer boxes

Key Operations in Sheet Metal Working

  • Cutting:

  • Process of removing material from the sheet metal to achieve desired shapes.

  • Bending:

  • Involves deforming the sheet metal along a straight line.

  • Bending Operations:

    • V-Bending: Utilizes a V-shaped die and punch.
    • Edge Bending: Bends the edge of the sheet metal piece.
    • Press Brake: Common method for low production runs.
    • Complicated Dies: Suitable for high production volumes.

  • Drawing:

  • Process where sheet metal is formed into three-dimensional shapes.

  • Involves a punch and die system.

  • Key factors include the clearance for drawing and the drawing ratio.

Bending Operations

  • Bending Allowance (BA):

  • Formula:

    • BA = 2πA(R + Kba)/360, where R is the inside radius.
    • Kba values depend on the relationship of R to thickness (t).
    • Kba = 0.33 if R < 2t
    • Kba = 0.5 if R ≥ 2t

  • Springback:

  • Occurs due to elastic recovery after bending.

  • Calculated as SB = (A' – A'b)/A'b; can be minimized by over-bending or bottoming.

Calculating Bending Forces

  • Bending Force Formula:
  • F = Kbf × TS × w × t² / D
    • TS = Tensile strength in MPa
    • Kbf values differ for V-bending (1.33) and edge bending (0.33).

Drawing Operations

  • Drawing Ratio Formula:

  • D = Db / DP < 2 (Db = Blank diameter, DP = Punch diameter)

  • Maximum draw ratio and reduction limits are important to prevent tearing and wrinkling.

  • Drawing Forces:

  • Maximum punch force: F = πDp × t × TS

  • Holding force: Fh = 0.015YY × Db² − Dp + 2.2t + 2Rd² (where Rd is die corner radius).

Typical Drawing Defects

  • Common issues include:
  • Flange Wrinkling
  • Wall Wrinkling
  • Earing
  • Surface Scratch
  • Tearing

Additional Sheet Metal Forming Operations

  • Ironing:

  • Reduces thickness and increases length without changing the outer diameter.

  • Coining and Embossing:

  • Add designs and patterns by pressing into the sheet metal.

  • Hydroforming:

  • Uses a fluid medium to shape the metal into complex shapes.

High Energy Rate Forming (HERF)

  • **Processes:
  • Explosive Forming
  • Electromagnetic Hydraulic Forming
  • Electro Hydraulic Forming
  • Applications in specialized manufacturing scenarios.

Additional Resources

  • Includes links to videos demonstrating sheet metal working techniques for further visual understanding.