BIZOMAT MAKEOS · Fabrication
Perforated Plate Design (Hole Size for Open Area, Punching Force, Ligament)
What hole size gives my target open area at this pitch, what force does a gang of punches need, and is the ligament between holes wide enough for the sheet?
Design of a perforated sheet: the hole diameter for a target open area at a pitch for 60° staggered or straight rows, open area, holes per square metre and sheet mass for the hole you choose (as the perforated open area tool), punching force for the punches working in one hit with a wear factor (as the punching force tool) against the press, and checks of the ligament and hole size relative to the sheet thickness.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Hole pattern | choice | Layout of the holes. |
| Open area wanted | % | Open area the screen or guard needs. |
| Hole pitch | mm | Centre distance between neighbouring holes. |
| Hole diameter chosen | mm | Hole diameter you intend to use. |
| Sheet thickness | mm | Sheet thickness. |
| Sheet area | m² | Area of the perforated sheet. |
| Sheet density | kg/m³ | Density of the sheet. |
| Holes punched per hit | Number of punches that cut in one press stroke. | |
| Shear strength of the sheet | MPa | Shear strength of the sheet. |
| Wear factor | Allowance for punch and die wear. | |
| Press capacity | kN | Rated capacity of the perforating press. |
| Least ligament ÷ thickness | Least ligament width as a multiple of thickness for flatness and strength (your value). | |
| Least hole ÷ thickness | Least hole diameter as a multiple of thickness for punch life (your value). |
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: Hole pattern
- What it is
- How the holes are laid out: staggered rows at sixty degrees (each hole surrounded by six equally spaced neighbours) or straight rows on a square grid.
- Units and format
- Choose one of 2 options from the list: 60° staggered; Straight rows.
- Example
- The form opens with “60° staggered” selected as a worked example. Choose the option that matches your case.
- Get it right
- The pattern changes the open area and the holes per square metre for the same hole and pitch.
What this means: Open area wanted
- What it is
- The share of the sheet area that must be open hole, set by the airflow, drainage, screening or guarding need. The tool gives the hole size that just achieves it.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 1% to 80%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 35% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Type the percentage itself, not a fraction.
What this means: Hole pitch
- What it is
- The centre-to-centre distance between neighbouring holes in the pattern.
- 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 8 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- For a given hole, open area falls with the square of the pitch.
- Get it right
- It is the centre distance, not the gap between hole edges (that is the ligament).
What this means: Hole diameter chosen
- What it is
- The diameter of the round hole you intend to punch, usually a standard punch size close to the hole the target open area needs.
- 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 5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Open area rises with the square of the hole diameter; punching force rises in proportion to it.
- Get it right
- It must be smaller than the pitch.
What this means: Sheet thickness
- What it is
- The thickness of the sheet being perforated. It sets the sheared length in each hole and the ligament and hole size checks.
- 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 1.5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Punching force is proportional to thickness.
What this means: Sheet area
- What it is
- The total area of the perforated sheet, used only to work out the sheet mass after the holes are removed.
- Units and format
- Enter a number in m²: square metres. The form accepts 0.000001 m² to 10000 m². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 m² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Sheet density
- What it is
- The mass per unit volume of the sheet material, from the supplier data sheet.
- Units and format
- Enter a number in kg/m³: kilograms per cubic metre. The form accepts 0.000001 kg/m³ to 20000 kg/m³. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 7850 kg/m³ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Type kg/m³, not g/cm³ (multiply g/cm³ by 1000).
What this means: Holes punched per hit
- What it is
- The number of punches in the tool that cut a hole in one stroke of the press.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 100000. Use a whole number. 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
- Force per hit is proportional to the number of punches cutting at once.
What this means: Shear strength of the sheet
- What it is
- The shear strength of the sheet material, the stress at which it shears through, from the supplier data sheet or material standard.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 2000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 300 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Punching force is proportional to it.
- Get it right
- Use shear strength, not tensile or yield strength.
What this means: Wear factor
- What it is
- A multiplier on the punching force that allows for dull punches and worn dies, which need more force than sharp tooling.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 2. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Force per hit rises in direct proportion.
- Get it right
- Take it from your tooling practice or the press maker; it is a multiplier, not a percentage.
What this means: Press capacity
- What it is
- The rated force capacity of the perforating press, from its nameplate or maker’s data. The force per hit is compared with it.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 250 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Type kilonewtons; tonnes-force must be converted (1 tf = 9.80665 kN).
What this means: Least ligament ÷ thickness
- What it is
- Your rule for the narrowest web of material between neighbouring holes, written as a multiple of the sheet thickness.
- Units and format
- Enter a plain number with no unit. The form accepts 0.3 to 5. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from your design or tooling rules.
What this means: Least hole ÷ thickness
- What it is
- Your rule for the smallest hole that can be punched reliably, written as a multiple of the sheet thickness, for punch life.
- Units and format
- Enter a plain number with no unit. The form accepts 0.3 to 5. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from your design or tooling rules.
Method and formulas
- Open area = 90.69 (d ÷ p)² % for 60° staggered or 78.54 (d ÷ p)² % for straight rows; hole for a target = p √(OA ÷ constant) (as the perforated open area tool).
- Holes per square metre = 1.1547 ÷ p² (staggered) or 1 ÷ p² (straight); mass = area × thickness × density × (1 − open area).
- Force per hit = holes × π d × t × τ × wear factor (as the punching force tool); ligament = p − d.
- Example: 35% at a 8 mm pitch needs 4.9699 mm holes; 5 mm gives 35.426% and 169.65 kN per hit of 20 holes.
Limitations
- Full field of holes; margins and blank areas reduce the overall open area.
- Flat-faced punches; staggered punch lengths lower the peak force.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Specify a perforated screen or guard
- Check a perforating tool against the press
- Trade hole size and pitch for open area and strength
Who it is for
- Fabrication supervisors
- Design engineers
- Press tool designers
What you get
- Hole size for the target open area
- Open area, holes and mass for the hole chosen
- Punching force and the ligament and hole checks
Interpreting the result
- Narrow ligaments make the sheet distort and the punches break: keep the ligament at least the sheet thickness.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2607–2608, 1338–1346. Topic reference; no source tables or recommended settings are reproduced.
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Open the Perforated Plate Design (Hole Size for Open Area, Punching Force, Ligament) calculator