To be able to produce injection molded parts with uniform quality in a changing process environment process parameters have to be adjusted. Those process parameters are either fixed for a specific reason or can be adjusted in a certain range. The aim of this thesis was to investigate the influence of a changing switch-over point and the injection speed on the successful use of a movable mold insert system and the weld line quality of valve plates. The other factors in this injection molding process that could be considered to have an impact on the functionality and the produced weld line quality of this system were fixed. To test the impact of those factors on the weld line quality a new test station was designed and manufactured. The test station is used to measure the weld line strength under bending load. It is capable of testing several types of valve plates in a quick and easy way. Two aspects were investigated during the testing. First, is the production process stable and second, can the injection speed be lowered and does the switch-over point influence the results. The process stability was examined by taking a look on shifts in weld line strength and changes in standard deviation over time. Even with a significantly changing mold temperature no significant trends or shifts could be found. The weld line strength was tested by tracking force over displacement of the weld line area until failing. The results showed that once all movable mold inserts are triggered reliably there is almost no change in weld line strength detectable. However, some settings were tested in which the movable mold inserts did not work in the intended way. These settings showed an unsatisfactory weld line strength although all movable mold inserts were triggered. These settings produced parts but did not reliably trigger all mold inserts or showed crinkles at the surface markings of the movable mold inserts. These settings can be used as the low end settings for future testing but cannot be used for a production run.