Injection Mould Clamp Tonnage From Projected Area

Both terms are got wrong in a way that shows up as flash. Projected area is the area seen ALONG the direction the mould opens -- not the surface area of the part, and not its footprint lying on a bench -- and it INCLUDES the runner, because a cold runner is pressurised plastic pushing the mould open exactly as the parts do. Leaving the runner out of a multi-cavity calculation is the common form of the error and it understates the requirement by enough to specify a machine that flashes. Cavity pressure is the term that moves most, and it is the one this cannot supply. It depends on the material's viscosity, the wall thickness, and the flow length the melt has to travel, and it ranges over roughly a factor of two between an easy part and a hard one of the SAME size -- so two parts with identical projected areas can want quite different machines. That is why the pressure is entered from a mould flow analysis or from experience with the material rather than taken from a table, and why a rule-of-thumb figure is a screen rather than a tool specification. The safety factor exists because the calculation is an estimate on both terms. The failure it guards against is not subtle: insufficient clamp lets the parting line open under injection pressure, and the part flashes at every shot until the machine is changed or the pressure is dropped far enough to short the part instead. Over-clamping is not free either -- it damages the mould's parting line over time and ties up machine capacity that a larger job needs -- so the answer is the right machine rather than the biggest available one. This sizes clamp force only. It does not compute cavity pressure, perform a mould flow analysis, size the injection unit or check the shot capacity, evaluate the platen size, tie-bar spacing or mould stack height that also decide whether a mould fits a machine, or address the venting and parting line condition that let a correctly clamped mould flash anyway. The moulder's process engineer, the mould designer, and the machine manufacturer's specifications govern.

clamp force = total projected area (parts plus runner, taken ALONG the mould opening direction) x cavity pressure, with a safety factor commonly 10 to 20%; the maximum cavity pressure a machine supports inverts it.

Injection moulding clamp sizing as the trade states it, with cavity pressure ENTERED (typically 2 to 5 tons per in2) because it depends on wall thickness, flow length and material viscosity rather than on part size, and a mould flow analysis rather than a table is what a serious tool is sized on.

One multiplication and one rearrangement.

Estimate. AHJ and licensed professional govern.

Field names used by the API: cavities, part_projected_area_in2, runner_projected_area_in2, cavity_pressure_tsi, safety_factor_pct, machine_rating_tons, total_area_in2, clamp_required_tons, clamp_with_safety_tons, runner_penalty_tons, margin_tons, max_cavity_pressure_tsi

• Cavity pressure is entered 2 to 5 tons per in2 typical, from geometry and materiala mould flow analysis
• Projected area includes the runner a cold runner pressurises the mouldstandard moulding practice
• Clamp only platen size, tie-bar spacing and stack height also decide fitthe machine manufacturer's specifications