| The present research focused on the investigation of the Vibration-Assisted Injection Molding (VAIM) process for improved manufacturing. The objective of this research was to explore the theory behind VAIM processing and illustrate via experiments how vibration alters mechanical properties.; The novel processing concept explored was based on using motion of the injection screw to apply mechanical vibration to polymer melts during the injection and packing stages of molding processes, which could be done with minimal machine modification and no mold modification. The goal in doing so is to control the polymer behavior at a molecular level without sacrificing process cycle time, and to eliminate a costly and time-consuming secondary process, which would yield improvements of the mechanical properties of molded products.; During the study the concept was verified experimentally by comparing the mechanical properties of polystyrene, virgin/recycled polystyrene blends, and polycarbonate products made using the VAIM technique with those made through optimized conventional processing. The resins utilized during the study were DOW STYRON 666D (polystyrene), PRCA PC-9000 (recycled polystyrene), and DOW CALIBRE 300EP22 (polycarbonate); The actual degree of strength improvement imparted in products was found to depend on material type. Furthermore, when the strength was enhanced, the degree of strength enhancement depended on at least four parameters, which are vibration frequency, vibration amplitude, vibration duration, and the delay time between the injection start and the vibration start. When these parameters were optimized for polystyrene, as much as a 28% strength improvement with an associated product standard deviation reduction of over 67% resulted. Also, the virgin/recycled polystyrene blends did not only show significant strength enhancements, but also their strengths exceeded that of the conventionally molded 100% virgin polystyrene. However, when the VAIM process was applied to polycarbonate, the degree of strength enhancement was very low. Moreover, the application of VAIM process on polycarbonate resulted in a toughness reduction.; The test results, which included the effects of VAIM process parameters on strength enhancements and its material dependency, were concisely reviewed. The conceptual mathematical description of resultant residual stresses and orientation in the VAIM processing was included and utilized to a potential theoretical basis for VAIM processing. Also, future directions for VAIM processing research were suggested based on the present investigation. |
