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How to Calculate the Clamping Force of an Injection Molding Machine?

Micro Injection Molding 2025-07-30 09:31:01

Mold cavity pressure

(For general low-end and simple products such as PP, PE, PS, ABS, calculations can be made using over 150 kg/cm². For engineering plastics with higher viscosity and thin-walled products, generally use 300 kg/cm². For high-end precision products, generally use over 300 kg/cm².)

Clamping force

It refers to the maximum force that can be withstood to separate the mold after it is closed. Generally, injection molding machines have a rated clamping force. If set too high, it may cause deformation of the machine or the mold.

The magnitude of clamping force is roughly proportional to the projected area of the part. A rough calculation method is as follows:

1. Clamping force (F) ≥ Mold cavity pressure (P) (kg/cm²) × Projected area of the molded part (S) (cm²)

Clamping force (tons) = projected area of the mold cavity (cm²) × material pressure coefficient ÷ 90% of the rated clamping force

Mold cavity pressure: (For general low-end simple products such as PP, PE, PS, ABS, a value above 150 kg/cm² can be used. For engineering plastics with higher viscosity and thin-walled products, 300 kg/cm² is generally used. For high-end precision products, a value above 300 kg/cm² is generally applied.)

Attachment: Material Pressure Coefficient Parameter Table:

Example: Two products are produced in one mold, among which: the product projected area = 10×17=170 cm², the runner projected area = 0.8×14=11.2 cm², the material used is ABS with an average pressure coefficient of 0.39, therefore: clamping force = (170+11.2)×0.39=70.67 tons, 70.67÷90%=78.5 tons.

If the machine model is determined based on the projected area of the product, although a clamping force of 80 tons is sufficient, it is still necessary to consider whether the gross weight of the product exceeds the maximum shot capacity of the machine (the maximum shot capacity of the 80-ton machine is 142 g). In addition, if the clamping force is greater than (or equal to) 85 tons, it is also important to consider the mold dimensions and product characteristics to determine whether a machine above 80 tons should be used.

The product specifications are quite stringent, and the machine's mold capacity cannot accommodate the mold, so generally a model with at least 120 tons is required.

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How to Calculate the Clamping Force of an Injection Molding Machine?

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