In-mold melt-front rate control using capacitive transducer in injection molding
by Feng Zhou
M.Phil. Chemical and Biomolecular Engineering
xiii leaves, 102 p. : ill. ; 30 cm
Injection molding, an important polymer processing technique, is a complex cyclic process, during which material properties, machine variables and process variables interact with each other in determining the final product quality....[ Read more ]
Injection molding, an important polymer processing technique, is a complex cyclic process, during which material properties, machine variables and process variables interact with each other in determining the final product quality.
Among injection molding, filling, packing-holding, and cooling are the most important phases. In the filling phase, melt-front rate plays a particularly important role in determining the part quality. Prior researches recommend a constant melt-front rate during the mold filling for producing uniform parts. However, it was practically difficult to measure the melt-front rate online. A novel measurement device, a capacitive transducer, has been proposed and developed by Gao’s research group. It has been shown that this transducer is effective in the online and continuous measurement of melt-flow position in mold cavity, the detection of start and end of filling, V/P transfer point, gate freezing time, and the quality monitoring. Therefore this sensor provides a basis for the control of the in-mold melt-front rate.
With such a sensor, this project develops and tests closed-loop control system of direct in-mold melt-flow control. Several different advanced control algorithms, including generalized predictive control (GPC), iterative learning control (ILC) and generalized 2D model predictive iterative learning control (2D-GPILC) are designed, and tested with different mold inserts. It is shown that 2D-GPILC, a combination scheme of feedback and iterative learning scheme, gives the best control result. From the application results, it can be concluded that melt-front rate has been successfully controlled to be constant based on the capacitive transducer.