KEVOS® MAKEOS · Manufacturing
Drop Hammer Forging Plan (Force Needed, Set per Blow, Number of Blows)
For upsetting or forging a part under a drop hammer, how far will each blow squeeze it, and how many blows will it take?
Plan of a drop hammer or drop stamp operation: the force needed to deform the part from its area, the flow stress at the forging temperature and a constraint factor, then the set per blow at which the hammer’s energy (falling mass, drop height and efficiency) gives that average force (as the drop hammer blow tool, solved for the set), the impact speed and energy per blow, and the number of blows for the total reduction, against the most blows you will allow per heat.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Falling mass (tup and die) | kg | Mass of the tup, die and anything else that falls. |
| Drop height before contact | m | Height the tup falls before it touches the work. |
| Blow efficiency (share into the work) | % | Share of the blow energy that goes into deforming the work (the rest goes into the anvil and foundation). |
| Part | ||
| Area being forged (average over the blow) | mm² | Cross-section area being squeezed, averaged over the blow. |
| Flow stress at forging temperature | MPa | Flow stress of the material at the forging temperature and strain rate. |
| Constraint (shape) factor | Factor for friction and die constraint (about 1.2–2 for open-die upsetting, more for closed dies). | |
| Total height reduction needed | mm | Total reduction in height the forging needs. |
| Most blows allowed per heat | blows | Blows you can strike before the part must be reheated. |
Method and formulas
- Force needed F = A × flow stress × factor.
- Average force of a blow F = η m g (h + d) ÷ d (as the drop hammer blow tool), solved for the set: d = η m g h ÷ (F − η m g).
- Blows = total reduction ÷ set per blow, rounded up; impact speed √(2 g h).
- Example: 450 kN is needed; each blow sets 13.191 mm, so 3 blows.
Limitations
- Constant area and flow stress; as the part spreads and cools the force rises and the set falls.
- Rigid anvil; a light anvil absorbs much of the blow.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Estimate the blows to upset a bar end
- Check whether a hammer is big enough for a forging
- Compare drop heights or tup masses
Who it is for
- Forge masters
- Manufacturing engineers
- Blacksmiths
What you get
- Force needed
- Set, energy and impact speed per blow
- Number of blows
Interpreting the result
- Doubling the drop height roughly doubles the set per blow; a heavier tup does the same with less impact speed.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 183–184. Topic reference; no source tables or recommended settings are reproduced.
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Open the Drop Hammer Forging Plan (Force Needed, Set per Blow, Number of Blows) calculator
