Abstract: Systems and approaches for controlling a molding machine having a mold forming a mold cavity and being controlled according to a mold cycle include injecting a molten polymer into the mold cavity. A first and a second sensor are used to obtain first measurements of respective first and second variables during the injection cycle. The second sensor is positioned downstream from the first sensor. The first and second sensors are used to obtain second measurements of the respective first and second variables during the injection cycle. A first difference value is determined between the first measurements of the first and second variables. A second difference value is determined between the second measurements of the first and second variables. The first and second difference values are compared, and at least one control parameter is adjusted based on a difference between the first and the second difference values.