To implement the VAIM process, a conventional injection molding machine is augmented by oscillating the injection screw (in the axial direction) during the injection and packing phases of the molding cycle.
For each material, two different sets of VAIM processing conditions and one set of conventional processing conditions were utilized described in Table 2.
For all three materials, when processed with the VAIM melt manipulation technique, there is a visible increase in relative orientation as evidenced by the birefringence patterns.
More evident is the significant increase realized from the VAIM processed parts.
Lehigh can adjust its VAIM process to move the part's weld line to any desired position.
In one VAIM trial, the Lehigh researchers enhanced the tensile strength of different grades of polystyrene.
Parts produced by VAIM also show improved mechanical properties in the transverse as well as the main flow direction.
The molding machine is configured to run in both conventional and VAIM mode.
Further discussion is presented below on the effects of vibration frequency and duration, pack pressure and melt temperature on the parts produced via VAIM.
Observation of the polymer melt behavior during VAIM was successfully accomplished using a custom-fabricated mold and associated image capture system.
If similar behavior is observed between this "delayed pack" injection molding mode and the vibration-assisted mode, this will provide further evidence that vibration in and of itself is not responsible for the higher degree of molecular orientation seen in parts produced via VAIM.