KEVOS® MAKEOS · Fabrication
Punching Operation Plan (Force, Stripping, Punch Stress, Clearance)
What force does this punching operation need with stripping, is the punch strong enough, what die clearance should I use, and is the press big enough?
Plan of a piercing or blanking operation: cut perimeter for a round or rectangular punch, cutting force with a factor for tool wear (as the punching force tool), stripping force as a share of it, total press load for the punches working together, compressive stress in the punch against your allowable and the smallest round punch for the thickness, die clearance per side from your percentage of thickness, the die opening, and the energy per hit from the penetration before breakthrough.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Punch shape | choice | Round or rectangular punch. |
| Punch diameter (round) | mm | Diameter of a round punch. |
| Punch length (rectangular) | mm | Length of a rectangular punch. |
| Punch width (rectangular) | mm | Width of a rectangular punch. |
| Punches cutting together | Number of punches that cut at the same moment. | |
| Sheet thickness | mm | Sheet thickness. |
| Shear strength of the sheet | MPa | Shear strength of the sheet (often about 0.7–0.8 of tensile strength). |
| Wear (dull tool) factor | Allowance for punch and die wear (as in the punching force tool). | |
| Stripping force share | % | Force to strip the sheet off the punch as a share of the cutting force (your value; typically 5–20%). |
| Allowable punch compressive stress | MPa | Allowable compressive stress for the punch steel and hardness (your value). |
| Die clearance per side | % of t | Clearance between punch and die on each side as a share of thickness (your value for the material and edge quality). |
| Penetration before breakthrough | % of t | Share of the thickness the punch enters before the slug breaks out. |
| Press capacity | kN | Rated capacity of the press. |
Method and formulas
- Perimeter: π d (round) or 2(a + b) (rectangular); cutting force F = perimeter × t × τ × wear factor (as the punching force tool).
- Stripping = share × F; press load = (F + stripping) × punches.
- Punch stress = F ÷ punch area; smallest round punch d_min = 4 t τ × factor ÷ σ_allow.
- Clearance per side = share × t; die opening = punch + 2 × clearance; energy per hit ≈ F × penetration × t.
- Example: a 20 mm hole in 2 mm sheet takes 45.239 kN plus 4.5239 kN stripping; the punch runs at 144 MPa.
Limitations
- Flat-faced punches; shear angles on the punch or die lower the peak force.
- Clearance shares vary by material and the edge quality wanted.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a press for a piercing tool
- Check a small punch for crushing
- Set die clearance for a material thickness
Who it is for
- Press tool designers
- Sheet-metal engineers
- Press operators
What you get
- Cutting, stripping and total press force
- Punch stress and smallest round punch
- Clearance, die opening and energy
Interpreting the result
- When the punch diameter nears the sheet thickness, the punch itself becomes the weak link.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1338–1346. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Punching Operation Plan (Force, Stripping, Punch Stress, Clearance) calculator
