Method for controlling the injection molding process of an injection molding machine

A multiple run injection molding process, comprising:

• (1) providing an injection molding machine having an injection molding mold which forms at least one cavity for an injection molded part to be produced;
• (2) introducing a melt into the cavity through an ingate and, thereafter, closing the cavity;
• and
• (3) opening the cavity after an optimum cooling time t1, wherein the optimum cooling time t1 is determined in accordance with the following steps:
• (a) determining the time profile of a mold wall temperature to obtain a temperature profile;
• and
• (b) using the temperature profile from a time start value over time indirectly in the form of an integral calculation under the temperature curve, with the integral being added under the temperature curve to determine when a predetermined limit value (t1) is reached wherein the limit value (t1) is the optimum cooling time at which the mold is opened and where (t1) is before the actual time (t2) at which the mold internal pressure reaches atmospheric pressure, and wherein the time start value is one of:
• (i) the time at which the maximum value of the mold wall temperature curve is reached,
• (ii) the time at which the switching time to the holding pressure takes place, and
• (iii) the time at which the maximum value of the mold internal pressure is reached;
• and
• (4) repeating steps (2) and (3) for each run of the injection molding process.