| The concept of melt modulation for enhanced cold runner based injection molding processing was investigated and further developed during the present research project. The primary goal of the work was to employ a science based approach to develop systems that both performed better and were more practical. Since its conception a decade ago, the technology has been proven to be very useful in several applications. These include cavity specific process control, family molding and weld line positioning. The original system was invented with the intention of supporting the benefits of melt modulation without focusing on the required overall system of components. The initial prototype system was bulky, expensive, lacking in efficiency, and therefore not suitable for typical applications in industry. This research was conducted in order to improve upon the previous system, and thus develop a new generation of enhanced melt modulation systems.;During the first phase of the work a compact and powerful melt control system was created to replace the original design. The associated new valve design was relatively small, less expensive and more efficient. Incorporated with a new control system which performed as a function of ram position, the new system involved the development of two different control techniques. The new control techniques were used in a series of experiments which determined the valve performance in comparison to that with the traditional control method. In addition, the effects of different control methods on part strength were investigated. A series of experiments were completed that showed an improvement in part strength versus molded products manufactured via the traditional control approach. Simultaneously, a coupled computational investigation of the new melt modulation concepts confirmed the results observed experimentally. The computational approach was then used to yield a final design of an enhanced system which is very suitable for implementations requiring several control valves.;The new generation of melt modulation systems is quite revolutionary compared to the design that existed prior to the current work. The enhanced melt modulation system developed is very practical and suitable for applications with several melt control locations. Four individual control valves were manufactured and used to test out the new design. To control all the valves efficiently, an optimization and control variable search method was also developed. This methodology was validated using both simulation and physical experimentation, the technique was proven to be very effective. It has an ability to locate valve control variables in a small number of iterative trials. Finally, a summary of the research and its impact are presented at the end of the dissertation, together with suggestions and recommendations for future research that would further improve this important area of polymer product manufacturing. |
