| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 89 === The hot runner with sequential valve-gate control can provide open/close capability at different time interval so that molding can proceed like relay race resulting in pressure reduction, residual stress minimization and weld-line deleting. However, the commercial valve gate systems exhibit unstable and inaccurate valve gate opening lending to the hesitation in industrial applications.
In this research a plate mold of 2mm thick with hot runner with sequential valve-gate control system was used to mold. In the process of mold design, we found the several key of the hot runner mold includes the heater choice, the location of thermal couple, reduce heat conduction effect, accurate of mold processes and design of cooling channel. The action of valve-gate control system will include human-machine interface capable of regulating with nitrogen pressure resulting in accurate response.
In the experimental we measured response time with no melt and melt in the mold. In the no melt experimental, we used four different piston diameters with various nitrogen pressure and the CCD camera will be used to monitor vale needle operation speed. In the other experimental, we added pressure sensor in the mold and the difference response time of the melt front across the pressure sensor between the open valve needle (without valve needle action) and valve needle action will be defined valve needle operation speed when the melt in the mold. Base on the experimental result, when the no melt in the mold, we found that the piston diameter 19.970mm with the nitrogen pressure 75Bar has the best response time. We also found that the response time will be reduced with the nitrogen pressure rise at the melt in the mold.
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