Injection molding · Machine sizing
Clamp Tonnage Calculator
Estimate injection molding clamp force from projected area and cavity pressure. This practical tool is an engineering estimate—validate decisions against machine, material, mold, and process data.
Decision chain
From estimate to the next check
- Parting planeCAD projection for every cavity and runner
- Pressure basisMeasured cavity pressure or a documented estimate
- Press screenClamp force with a stated margin
- Separate checksTie bars, platen, mold height, injection unit, and ejection
Formula and method
Clamp tonnage = projected area × estimated cavity pressure × safety factor.
Inputs and units
Enter measured or specified values in the displayed units. Keep units consistent; results are rounded for practical planning. This first release uses the displayed engineering units rather than a unit-switcher.
Worked example
100 in² × 4,000 psi × 1.10 ÷ 2,000 = 220 US tons.
Get the inputs from the parting plane
Take projected area from CAD on the mold-opening plane for every cavity and runner. Use a documented cavity-pressure basis from validated process data, simulation, or a conservative engineering estimate; machine hydraulic pressure is not the same input.
Reference basis: KEYENCE injection molding formulas.
Use the result in a press screen
Compare the estimate with rated clamp force, then separately check tie-bar spacing, platen size, mold height, injection-unit capacity, and ejection requirements. Clamp force alone cannot select a machine.
Sanity check before quoting
Doubling a genuinely identical cavity layout should double the projected-area contribution. If it does not, recheck whether cavity count or runner projection has already been included.
Interpretation, assumptions, and limitations
FAQ
Can I enter machine injection pressure as cavity pressure?
No. Pressure losses between the injection unit and cavity can be material and mold dependent. Use measured cavity pressure where available or document the estimate and margin.