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Calculation of the Stiffness and Strength of the Plastic Injection Mold

Calculation of the Stiffness and Strength of the Plastic Injection Mold

  • 2022-09-09

Calculation of the Stiffness and Strength of the Plastic Injection Mold

--China Plastic Injection Mold Maker Lyter Engineering Ltd share


For quality plastic injection molds, when the plastic melt is filling the cavity, the pressure on the cavity gradually increases. When the cavity is completely filled, the pressure in the cavity reaches the maximum value. Then, as the plastic melt cools, the pressure gradually decreases, and the pressure in the cavity after the plastic is completely solidified drops to close to normal pressure. In this process, each pressure-bearing surface of the mold cavity (cavity sidewall, bottom plate or support plate) must have sufficient rigidity and strength to prevent the mold cavity from being deformed or damaged and cracked under the action of high pressure. Therefore, when designing the mold, the stiffness or strength of the cavity side wall, bottom plate or support plate must be calculated.


The stiffness calculation of the side wall, bottom plate or support plate of the mold cavity is to control the amount of deformation, to ensure that the molten plastic does not overflow during the filling process, to ensure the thickness of the product, and to ensure that the product can be demolded smoothly in molds like Automotive Plastic Injection Tooling Moulding. The maximum deformation should be less than or equal to the shrinkage of the product wall thickness (especially important for precision plastic products) or the maximum allowable gap for the molten plastic to not produce overflow(flashes).


The strength of the mold refers to the plastic deformation or permanent deformation of the mold, that is, it is destroyed. The strength calculation of the mold is to check whether the tensile, shearing and bending stress of the mold during the working process exceeds the allowable limit stress.