Method and apparatus for injection molding of plastic materials

A method for injection molding of plastic materials into a cavity of a mold by a molding apparatus to create a molded article during an injection cycle including at least one injector supplied with fluid plastic material under pressure and including a pin valve displaceable between a fully closed position and a maximum opening position during the injection cycle, and vice versa, wherein the pin valve is driven in a controlled fashion with respect to its position and speed during displacements thereof, the method comprising:

• during a filling step of the injection cycle, initially moving the pin valve during opening displacement from the fully closed position upstream to a first partially opened position at a first speed, wherein the first speed is a maximum displacement speed of the pin valve during the opening displacement and during a closing displacement of the injection cycle;
• temporarily stopping the pin valve at the first partially opened position for a first determined period of time during the filling step;
• moving the pin valve, during the filling step and after the temporarily stopping, upstream at a second speed to a second partially opened position that is less than a maximum opening displacement or position of the pin valve during the opening displacement, wherein the second speed is less than the first speed;
• moving the pin valve upstream during the filling step to a third position at a third speed that is less than the first speed, wherein the third position is the maximum opening position of the pin valve during the injection cycle;
• temporarily stopping the pin valve at the third position for a second determined period of time;
• and
• during a subsequent packing step and during a closing displacement of the pin valve, moving the pin valve downstream to the fully closed position.