During the mold injection, the plastic injected in the product cavity creates a pressure on the core and cavity sides. To prevent the opening of the mold during the plastic injection, the press must apply a force to counterbalance this pressure (usually expressed in tons). The minimal force required to counterbalance the pressure can be approximated by taking into account the characteristics of the material, and a total area based on:
By comparing this minimal closing force and the maximal force of the available presses, a mold designer can confirm and accept a job or not. At this early stage, an approximate value of the minimal closing force is sufficient. In particular the area of the hot runners is not required. The projected area value can be retrieved from the Pulling Direction Analysis. |