Development of an Integrated Melt Modulation System to Manipulate Cold-Runner Injection Molding Processing Parameters and Their Effects on Final Product Physical and Optical Properties

Packing processing parameters, including packing pressure and packing time, have significant impact on the internal molecular orientations, mechanical properties and optical performance of injection molded polymeric products. One of the limitations of cold-runner injection molding machines is the lack of real-time control of packing processing parameters during an injection molding cycle. As a result, a new melt modulation device has been developed and experimentally validated to control melt flow and manipulate processing parameters during cold-runner manufacturing. The use of the integrated melt modulation device has shown enhancement of physical properties and optical performance of injection molded polymeric products. Numerical simulations and experimental results of common thermoplastic optical polymers, such as PMMA, PC, and GPPS have been conducted and briefly demonstrated herein.

Development of Multiple Melt Modulation Valves for Enhanced Injection Molding

New melt modulation system with multiple control valves was successfully developed to facilitate melt control in cold runner based injection molding. The entire valve mechanism and port geometry were significantly improved. The new valve gave better control characteristic and can be made inexpensively. Valve driving mechanism was also redesigned to be more compact and easy to be installed in a limited mold space. It allows four control valves to be placed in the same mold in which only two original valves were able to fit. The four valve melt modulation performed on a runner system that the effect of melt flow from each valve was influenced by all other valves. The interaction between four valves caused complicated behavior and also a difficulty to establish valve control parameters. A reciprocal search method was utilized and able to determine valve control variables within a reasonable number of trials. Experimentation was done on a potential case study that included both family molding and weld line positioning problems. As a part of the outcome, a simple gain modification was developed and able to find an optimum solution. The technique was carried out in both traditional fixed angle and new developed Bang-Bang control methods. The results shows that melt modulation system with multiple control valves was able to effectively control melt behavior and enhanced filling process.

A Variable Search Technique for Multiple Control Valves Used in Melt Modulation During Injection Molding

A variable search technique was investigated for use with a melt modulation system with multiple control valves. The method was developed in order to obtain an optimum solution which determines the positions of all valves. It was shown that not all valve angles in the system had to be determined, as only certain significant valves needed to be fine tuned during the searching process. It was also shown that the valve position and location were greatly dependent on the cavity and runner configurations. Once the valve control variable search method had been established, a series of family mold models was created and analyzed using MoldFlow. Instead of using the default runner from the software, a modification of the 3D models was made in order to embed melt modulation valves. The result showed that within a limited number of trials, an optimum solution can be obtained. The number of searching trials can also be reduced by applying different search gains and changing certain appropriate initial values.