Mechanical presses are extensively utilized across various industries for metal forming processes, including stamping, punching, and forging. The clutch system within a mechanical press is vital for transmitting power from the flywheel to the crank-slider or knuckle-joint mechanism, thereby regulating the press’s operation.

Choosing the appropriate clutch for a mechanical press necessitates a thorough evaluation of torque requirements to guarantee efficient and dependable performance.

Torque calculation for mechanical press clutch based on eccentric mechanism. Torque calculation for mechanical press clutch

Definitions

  • M — Transmission of torque by the crankshaft
  • F — Rated press tonnage
  • L — Length of connecting rod
  • r — Eccentricity of the crankshaft (stroke/2)
  • ß — Angle between the connecting rod and the movement direction of the ram at the rated distance
  • α — Crankshaft angle
  • s — Rated distance
  • x — Distance of the connection point of crankshaft and connecting rod to BDC at the rated distance

Calculation Steps

  1. Consider applying F (rated force over the distance s).
  2. The force components on the ram will be F and F_guide = F × tan(ß).
  3. Two forces act between the crankshaft and the connecting rod: F and F_guide.
  4. Torque formula: M = F·r·sin(α) + F_guide·r·cos(α)
  5. Simplified: M = F·r·sin(α + ß) / cos(ß)
  6. Let i represent the reduction ratio of the press gear system.
  7. To ensure sufficient force without slipping: M_clutch = M × i

Clutch Torque Graph Clutch Torque Graph

Finally, to select the appropriate clutch, refer to clutch manufacturer catalogues ensuring M_catalogue > M_clutch.

Conclusion

Selecting the appropriate clutch capacity is crucial for both manufacturers and stamping companies:

  • Over-sized clutch: Dimensional challenges, complicated press crown design, difficult maintenance, drive system damage on overload.
  • Under-sized clutch: Insufficient force transfer, clutch slippage, accelerated wear of friction plates, increased maintenance frequency.

The right clutch selection ensures effective force transmission, reduces maintenance frequency, and protects the crankshaft, connecting rod, gears, and other components from overload damage.

Emrah Demirezen — Metal Forming Specialist, Press Designer
info@demirezenengineering.com