Clamping Force Calculator
Calculate the required clamping force based on the projected area of the part, injection pressure, and number of cavities. Clamping force is the key parameter for machine selection — insufficient clamping force causes the mold to open during injection, resulting in flash and dimensional problems.
Input Parameters
Results
Fill in the data and click Calculate
ARGUS automatically selects force parameters based on part geometry and material
Clamping force is one of the primary machine selection parameters — ARGUS simultaneously considers shot size, tie-bar spacing, and required injection speed.
How do we calculate clamping force?
Clamping force is the force that the injection molding machine must exert on the mold to counteract the pressure of the melt in the cavity. If clamping force is insufficient, the mold opens during injection, causing flash and dimensional problems. It is typically the primary classification parameter for injection molding machines — expressed in kN or tons.
The calculator uses a pressure-area formula incorporating a safety factor and number of cavities.
F — clamping force [kN]
A — projected area of part [cm²]
p — injection pressure [bar]
n — number of cavities
k — safety factor (1.1–1.5)
Projected area is the projection of the part onto the mold parting plane — the sum of all cavity areas and runner channels. Cavity pressure is lower than injection pressure due to pressure drops in the runner and gate. Typically cavity pressure is 30–60% of injection pressure. A safety factor of 1.1–1.2 is used as standard; 1.3–1.5 for precision parts or high-pressure materials.
Cavity pressure for typical materials
Cavity pressure depends on material, wall thickness, and flow path length:
ABS, PS — 300–500 bar
PA6, POM — 400–700 bar
PC, PMMA — 500–800 bar
Thin-walled — 700–1200 bar
Rule of thumb: for standard parts, 3–5 kN/cm² of projected area can be assumed. For multi-cavity molds, projected area includes all cavities plus runners. In hot runner systems, runner area is eliminated, reducing the required clamping force.
Clamping force and machine size
Injection molding machines are classified primarily by clamping force: 25–6500 tons. Clamping force determines machine size, tie-bar spacing, and platen dimensions. When selecting a machine, check simultaneously: clamping force, barrel capacity (shot size), tie-bar spacing (mold dimensions), and mold height (min/max). ARGUS verifies all these parameters at once.
ARGUS automatically selects the machine based on clamping force, shot size, and mold dimensions
See it for yourself — book a presentation and discover how ARGUS combines force analysis with your plant's machine database.