Thermoplastics injection molding involves plastication followed by the injection of the melt into a cold cavity. Packing is employed to compensate for shrinkage due to cooling. Ultimately, the solidified part is ejected from the mold without damage. The successful operation of an injection molding machine requires control of the process variables during each of the consecutive stages in addition to correctly identifying the points of transition from one stage to the next. / Pressure and its variation during the injection molding cycle play an important role with regard to productivity, product quality, and product reproducibility. From the practical point of view, it is necessary to consider simultaneously hydraulic pressure, nozzle pressure, and the distribution of pressure in the cavity. Control of each phase of the injection molding process is best achieved by controlling one or a combination of the above pressure parameters. The present work describes a comprehensive study of the dynamics and control of pressure during each stage of the injection molding cycle. / Deterministic models were obtained for cavity gate pressure during the filling and packing stages. Dynamic model predictions were in good agreement with experimental data. The response of cavity gate pressure exhibited nonlinear behavior which was investigated and rectified by a gain scheduling control strategy. Stochastic models were obtained for cavity gate pressure response in the filling stage for the purpose of comparison and future design of more advanced control algorithms / The dynamic models were employed to design and evaluate control schemes for the injection molding cycle. Nozzle and cavity pressures were used in conjunction with PI, PID and Dahlin controllers. The hydraulic system of the injection molding machine was redesigned to incorporate two servovalves in order to achieve control over the cavity pressuretime profile during the packing stage as well as over peak cavity and hold pressures. The control loops were designed through a simulation study which also gave good indications of system limitations. / On the basis of this study, very good and reliable integrated control over the filling, packing, and holding stages was achieved by a general control scheme which allows the transfer of control from one variable to another during the various stages of the process.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.75857 |
| Date | January 1988 |
| Creators | Abu Fara, Dib I. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000732582, proquestno: AAINL48591, Theses scanned by UMI/ProQuest. |
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