Low flux values, one of the key properties of the final product, were detected in the company’s production process, resulting in an increased rejection rate. Due to incomplete routine production data, a comprehensive quality analysis of the existing situation was not possible. Therefore, the objective of this master’s thesis was to design and conduct an experiment to determine the effects of individual variables on flux, based on the analysis of available production data.
Based on an initial analysis of existing production data and the experience of company employees, the variables included in the experimental design were selected with appropriate combinations: magnetic property of material 1 and 2, cage intensity, tool temperature 1 and 3, and dryer temperature. After conducting the experiment, the products were measured, and the collected data were analyzed using linear mixed models, which, in addition to fixed effects, also allow for the inclusion of the random effect of the tool. Model selection was performed using elastic net regularization, with an emphasis on the LASSO method, to identify statistically significant interactions. The reliability of the selected model was further assessed through model stability analysis.
The analysis of the designed experiment showed that flux increases with higher magnetic property of material 1, higher cage intensity, and higher tool temperature 1, as well as with lower magnetic property of material 2 and lower dryer temperature. An interaction was identified between cage intensity and the magnetic property of material 2. The variable tool temperature 3 was not found to be statistically significant. The linear mixed model also revealed a significant random effect of the tool, indicating the presence of additional sources of variability not captured by the included variables.
Based on the designed experiment analyzed using linear mixed models, the key process parameters affecting flux were identified. This enables the company to appropriately adjust process parameters in cases of insufficient flux values. Finally, guidelines for further research on influencing factors are also provided.
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