KEVOS® MAKEOS · Manufacturing
Rubber Pad (Guerin) Forming Pressure and Pad Thickness Check
In rubber pad (Guerin) forming, what pressure does the pad put on the blank for my press capacity and pad area, is it enough for the part, and is the rubber pad thick enough for the height of the form block?
Rubber pad forming (the Guerin process) by the handbook: the total pad forming pressure p = F × 2000 ÷ A (F press capacity in tons, A pad area in square inches), here in SI as press force divided by pad area, compared with the forming pressure your part needs, and the pad thickness against the height of the rigid form block (usually three times the block height and never less than 1.5 times), with the pad hardness against the 50 to 70 Shore range the handbook gives.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Press and pad | ||
| Press capacity (force) | kN | Force the press can apply to the pad container. |
| Area of the pad | mm² | Area of the rubber pad in its container, in plan. |
| Thickness of the rubber pad | mm | Thickness of the rubber or polyurethane pad. |
| Hardness of the pad | Shore A | Durometer hardness of the pad; the handbook gives 50 to 70 Shore for Guerin pads. |
| Part | ||
| Height of the form block | mm | Height of the rigid form block above the press bed. |
| Forming pressure the part needs | MPa | Pressure the part needs to form fully, from your trials or forming data for the material, thickness and smallest radius. |
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.
Press and pad
What this means: Press capacity (force)
- What it is
- Force the press can apply to the rubber pad container.
- 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 4000 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The pad pressure grows in proportion.
- Get it right
- Take the rated capacity from the press plate; 1 short ton = 8.896 kN, 1 tonne-force = 9.807 kN.
What this means: Area of the pad
- What it is
- Area of the rubber pad in its container, seen in plan.
- Units and format
- Enter a number in mm²: square millimetres. The form accepts 0.000001 mm² or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400000 mm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The pad pressure falls as the area grows.
- Get it right
- Use the inside length times width of the pad container.
What this means: Thickness of the rubber pad
- What it is
- Thickness of the rubber or polyurethane pad.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 150 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Sets the pad thickness check against the form block height.
- Get it right
- Measure the pad itself, not the container depth.
What this means: Hardness of the pad
- What it is
- Durometer hardness of the pad material in Shore A.
- Units and format
- Enter a number in Shore A: Shore A. The form accepts 10 Shore A to 100 Shore A. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 60 Shore A as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Only moves the hardness check.
- Get it right
- Take it from the pad supplier; the handbook gives 50 to 70 Shore.
Part
What this means: Height of the form block
- What it is
- Height of the rigid form block above the press bed.
- 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 50 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Sets the pad thickness needed.
- Get it right
- Measure from the bed to the top of the block, including any spacer.
What this means: Forming pressure the part needs
- What it is
- Pressure the part needs on its blank to form fully.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 1000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 7 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Only moves the pressure check.
- Get it right
- Take it from trials or forming data for the material, thickness and smallest radius.
Method and formulas
- Pad pressure p = press force ÷ pad area (handbook: p = F × 2000 ÷ A psi with F in tons and A in square inches).
- Pad thickness ÷ form block height: usually 3, at least 1.5.
- Pad hardness: 50 to 70 Shore.
- Example: 4000 kN on a 400000 mm² pad gives 10 MPa against 7 MPa needed; the pad is 3 times the form block height.
Limitations
- The pressure is an average over the pad area; it is uniform on the blank, which is why the process thins the material very little.
- Radii formed by a rubber pad are larger than those from rigid dies; very small radii need more pressure or a different process.
- The forming pressure the part needs is not calculated here; enter it from trials or forming data.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check that a press can form a part by the rubber pad process
- Size the pad container area for a forming pressure
- Check the pad thickness for a form block
Who it is for
- Sheet metal tooling engineers
- Aerospace fabricators
- Press shop supervisors
What you get
- Pad forming pressure
- Pressure against the pressure needed
- Pad thickness as a multiple of the form block height
- Pad hardness against the usual range
Interpreting the result
- A smaller pad (or container) raises the pressure for the same press; several small parts on one table share the pad area.
- A pad thinner than 1.5 times the block height is overstrained and wears quickly.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1364–1365. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These KEVOS® Library readings explain the method this tool uses, with worked examples.
Useful alongside · KEVOS® original book
Draw, spin or something else
In Deep Drawing and Spinning by the Numbers
What it covers: Choose between drawing, spinning and other routes by quantity: tooling and unit costs, break-even, cost per part across volumes, uncertain demand, and catch tooling costed over a contract not yet won.
KEVOS® 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 Rubber Pad (Guerin) Forming Pressure and Pad Thickness Check calculator