Plastic article forming apparatuses and methods for controlling melt flow

A process of forming a molded article using an injection molding apparatus, the process comprising:

• selecting a first thermoplastic material for forming the molded article using the injection molding apparatus, wherein the first thermoplastic material has a first starting MFI having a first range of variability;
• selecting a second thermoplastic material for forming the molded article using the injection molding apparatus, wherein the second thermoplastic material has a second starting MFI having a second range of variability that is different from the first range of variability;
• providing the first thermoplastic material to the injection molding apparatus in a first molding operation and providing the second thermoplastic material to the injection molding apparatus in a second molding operation;
• heating the first thermoplastic material in the first molding operation and heating the second thermoplastic material in the second molding operation such that the first thermoplastic material and the second thermoplastic material are in a molten state in their respective first and second molding operations;
• injecting the molten first thermoplastic material into at least one mold cavity of the injection molding apparatus using an injection element in the first molding operation and injecting the molten second thermoplastic material into the at least one mold cavity of the injection molding apparatus using the injection element in the second molding operation;
• monitoring melt pressure of the first thermoplastic material and the second thermoplastic material filling the at least one mold cavity using a sensor, the sensor providing a signal indicative of melt pressure to a controller;
• the controller controlling the injection element thereby changing melt pressure of the first thermoplastic material and the second thermoplastic material filling the at least one mold cavity based on the signal;
• and
• reducing a mold temperature of the first thermoplastic material within the at least one mold cavity in the first molding operation and reducing the mold temperature of the second thermoplastic material within the at least one mold cavity in the second molding operation to form a molded article.

An injection molding apparatus that adjusts for changes in thermoplastic material melt viscosity in real time, comprising:

• a hopper that introduces a thermoplastic material to the injection molding apparatus;
• an injection element that receives the thermoplastic material from the hopper and moves the thermoplastic material toward an injection nozzle while heating the thermoplastic material to a molten state, the injection nozzle configured to inject the molten thermoplastic material into a mold cavity;
• a sensor that is arranged and configured to provide a signal that is indicative of melt pressure within the mold cavity;
• a controller that receives the signal from the sensor and comprising a processor and a memory containing computer readable and executable instructions which, when executed by the processor, cause the controller to automatically control the injection element thereby changing melt pressure of the thermoplastic material filling the at least one mold cavity based on the signal to reach a target cavity pressure saved in the memory.