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.

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.

Use this when screening a press

Start after the complete parting-line projection is known. A higher result means the mold needs more force to resist opening; it does not confirm tie-bar spacing, mold height, injection capacity, or platen suitability.

What changes the result most

Total cavity and runner projection, actual cavity pressure, and the chosen margin dominate. Do not substitute machine hydraulic pressure for cavity pressure.

Common mistake

Omitting runner projection or multiplying a one-cavity area twice gives a misleading press requirement.

Interpretation, assumptions, and limitations

This tool provides an estimate for planning and education. It does not replace machine maker limits, material data sheets, mold trials, cavity-pressure data, process validation, or qualified engineering review.

FAQ

Can I use this as a final production setting?

No. Confirm with validated process data and the applicable machine and material documentation.

Why can the real result differ?

Geometry, melt behavior, pressure loss, material lot, temperature, cooling layout, and operating practice can materially affect results.