• Ignjatovska Anastasija Faculty of Mechanical Engineering, “Ss. Cyril and Methodius” University in Skopje, P.O. Box 464, MK-1001 Skopje, Republic of North Macedonia
  • Tomov Mite Faculty of Mechanical Engineering, “Ss. Cyril and Methodius” University in Skopje, P.O. Box 464, MK-1001 Skopje, Republic of North Macedonia




design of experiments, non-standard fraction-factorial design, injection molding, model validation


A structured approach is fundamental in designing a complex multivariable process, while achiev-ing specified product quality. Nominal values of process parameters of an injection molding process are defined by implementing DOE methodology. Optimisation of experimental phase is achieved by progressive information acquir-ing concerning influential input factors and DOE design. Hence, most influential machine process parameters are varied using a non-standard fraction-factorial design. A linear regression model with included elements of second order inter-action is defined based on obtained data. Additional testing of its validation is in order before reaching a final conclu-sion. Firstly, model significance is tested by conducting an ANOVA analysis. Only significant models prove that DOE has been adequately planned and factors which affect the controlled output have been chosen. Finally, DOE is com-pleted by adequacy analysis of the regression model. Lack-of-fit test is chosen to test whether the model is a proper representation of the real process.


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