BIZOMAT MAKEOS · Fabrication
Press Tonnage for a Compound or Progressive Die
What total press force does this die need for blanking, piercing, bending and drawing together, and is the press big enough?
Total press load for a compound or progressive die stage by summing the handbook forces for blanking and notching (perimeter × thickness × shear strength), piercing a number of holes, bending (L T² × UTS ÷ die opening) and a first draw (π d T × UTS), plus stripping force and a safety margin, with the cutting energy per stroke and the press capacity check.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Material thickness | mm | Sheet thickness. |
| Shear strength | MPa | Shear strength of the sheet (often about 0.8 × tensile strength). |
| Tensile strength | MPa | Ultimate tensile strength. |
| Operations (0 = none) | ||
| Blanking and notching perimeter | mm | Total length cut at once around blanks and notches. |
| Number of holes pierced | Number of holes pierced in the same stroke. | |
| Hole diameter | mm | Diameter of each pierced hole. |
| Length of bends | mm | Total length bent in the stroke. |
| Bend die opening | mm | Opening of the bending die. |
| Mean diameter of a first draw | mm | Mean shell diameter of a first draw in the same stroke. |
| Allowances | ||
| Stripping force (share of cutting force) | % | Force to strip the strip off the punches. |
| Press safety margin | % | Margin above the calculated load when choosing a press. |
| Penetration at fracture (share of thickness) | % | Share of thickness the punch penetrates before fracture (for cutting energy). |
| Press capacity | kN | Rated press capacity. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Material thickness
- What it is
- The thickness of the sheet or strip being cut, bent or drawn in the die.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 50 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cutting and drawing forces rise in proportion to thickness; bending force rises with its square.
What this means: Shear strength
- What it is
- The shear strength of the sheet material, used for the blanking, notching and piercing forces.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 3000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 350 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- All cutting forces are directly proportional to it.
- Get it right
- Shear strength, not tensile strength; take it from material data for the sheet.
What this means: Tensile strength
- What it is
- The ultimate tensile strength of the sheet material, used for the bending and drawing forces.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 3000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 450 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Operations (0 = none)
What this means: Blanking and notching perimeter
- What it is
- The total length of edge cut in one stroke by the blanking and notching punches, all the way round their outlines.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 1000000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Blanking force rises in direct proportion to this length.
- Get it right
- Add every blanking and notching edge cut in the same stroke; enter 0 if there is none.
What this means: Number of holes pierced
- What it is
- How many holes are pierced in the same press stroke, all at the one hole diameter.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 10000. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Holes of other sizes can be added to the blanking length as their perimeter instead.
What this means: Hole diameter
- What it is
- The diameter of each pierced hole; every hole counted is taken at this size.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Length of bends
- What it is
- The total length of bend line formed in the same stroke.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Bending force rises in proportion to the bend length.
- Get it right
- 0 means there is no bending operation.
What this means: Bend die opening
- What it is
- The width of the opening in the bending die, across which the sheet is bent.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 16 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A wider die opening lowers the bending force in proportion.
- Get it right
- Only used when there is a bend length.
What this means: Mean diameter of a first draw
- What it is
- The mean diameter of the shell in a first draw done in the same stroke, measured to the middle of the wall.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 5000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- 0 means no drawing; mean diameter is outside diameter minus one thickness.
Allowances
What this means: Stripping force (share of cutting force)
- What it is
- The force needed to strip the material off the punches, as a percentage of the total cutting force.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 50%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Press safety margin
- What it is
- The extra capacity you want above the calculated load when choosing a press, as a percentage.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Required press force = total load × (1 + margin ÷ 100).
What this means: Penetration at fracture (share of thickness)
- What it is
- How far the punch enters the sheet before the material fractures, as a share of the thickness; used only for the cutting energy.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 5% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 40% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cutting energy rises in proportion; the force results are unchanged.
What this means: Press capacity
- What it is
- The rated force capacity of the press you plan to use for the die.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 1000000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 600 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- It does not change the forces; it sets the pass or fail check.
- Get it right
- Presses are often rated in tonnes: 1 tonne-force is 9.807 kN.
Method and formulas
- Blanking and notching: F = perimeter × t × τ; piercing: F = holes × π d × t × τ.
- Bending: F = L t² UTS ÷ W (handbook formula 36); first draw: F = π d t UTS (formula 44).
- Total = cutting forces × (1 + stripping) + bending + drawing; required press = total × (1 + margin).
- Cutting energy ≈ cutting force × thickness × penetration share.
- Example: the default die needs 404.76 kN, or 485.71 kN with margin.
Limitations
- Peak forces assumed to coincide; staggering punch lengths or shear on punches lowers the peak.
- Press capacity is usually rated near the bottom of the stroke.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a press for a new die
- Check a progressive die against press capacity
- Estimate cutting energy for a flywheel press
Who it is for
- Toolmakers
- Press shop engineers
- Estimators
What you get
- Force for each operation
- Total and required press force
- Cutting energy and capacity check
Interpreting the result
- Check the press rating at the point in the stroke where the peak occurs, not just its nominal tonnage.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1336–1359, 1386–1392. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · Library collection
Press tools and dies: how sheet metal parts are blanked, pierced and formed in volume
What it covers: How press tools work, punch and die clearance, estimating press force, single, compound, progressive and transfer dies, strip layout, forming and springback, press safety and when tooling pays.
BIZOMAT 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 Press Tonnage for a Compound or Progressive Die calculator