KEVOS® MAKEOS · Fabrication
Mechanical (Crank) Press Capacity Above Bottom
How much force can this crank press deliver at the height where my operation happens, and is it enough?
Force available from a crank press at any height above bottom dead centre: the slider-crank geometry gives the slide position against crank angle, the rated crankshaft torque follows from the rated force at the rating point, and the available force at the working height is that torque divided by the slide’s mechanical advantage there (capped at the frame rating), with the energy of the working stroke.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Rated force | kN | Nominal tonnage of the press. |
| Rating point above bottom | mm | Height above bottom dead centre at which the nominal tonnage is rated (often 3–13 mm). |
| Stroke | mm | Slide stroke (twice the crank radius). |
| Connecting rod length | mm | Centre distance of the connecting rod. |
| Force needed by the operation | kN | Force the die needs. |
| Height above bottom where the force starts | mm | Height above bottom where the die starts working (for blanking, the material thickness above bottom; for drawing, the draw depth). |
| Working distance (until bottom) | mm | Distance over which the force acts. |
| Flywheel energy available per stroke | kJ | Energy the flywheel can give per stroke without slowing too much (from the press maker). |
Method and formulas
- Slide height above bottom h(θ) = r (1 − cos θ) + L − √(L² − r² sin² θ), with r = stroke ÷ 2 and θ from bottom.
- dh/dθ = r sin θ [1 + r cos θ ÷ √(L² − r² sin² θ)]; rated torque T = F_rated × dh/dθ at the rating point.
- Force available at height h = T ÷ dh/dθ there, capped at the rated force.
- Working energy ≈ force × working distance.
- Example: a 1000 kN press rated 6 mm above bottom gives only 581.61 kN at 20 mm.
Limitations
- Crank (eccentric) drives; link and knuckle presses have different curves.
- Press makers publish the official capacity curve; use it for final selection.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check whether a press can blank or draw high in the stroke
- Choose between presses with different rating points
- Explain why a press stalls on deep draws
Who it is for
- Press shop engineers
- Toolmakers
- Manufacturing engineers
What you get
- Crank angle at the working height
- Force available there
- Working energy against flywheel energy
Interpreting the result
- Blanking happens near the bottom; drawing starts high in the stroke where capacity falls away quickly.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1386–1392, 1342. Topic reference; no source tables or recommended settings are reproduced.
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Open the Mechanical (Crank) Press Capacity Above Bottom calculator
