In the production of wall and floor ceramic tiles, mixtures of raw materials from several origins with different physical and chemical characteristics are used. Those changes of raw materials alter the quality of the finished product, what implicates in the constant reformulation in the composition of the ceramic mass through try and error, consuming time and materials. This configures the ideal circumstance to apply the techniques of experiments design, often used in many areas to model properties of such ceramic bodies. In the present study, 21 formulations of six raw materials, namely talc, quartz, calcareous, phyllite, dolomite and clay were selected and used as control factors in the experiments design. Those formulations were processed under conditions similar to those used in the ceramics industry: powder preparation (wet grinding, drying, granulation and drying), green body preparation (pressing and drying), firing (at 1180 ºC) and characterization. With the experimental results, regression models were calculated, relating bending strength, linear firing shrinkage and water absorption. After statistical analysis and verification experiments, the significance and validity of the models were confirmed, and one technique for optimization of ceramic bodies was developed: a mathematical expressions denominated loss of quality function. The regression models and the developed technique of the loss quality can then be used for the best combination of those six raw materials to produce a ceramic body with specified properties. Keywords: mixture experiments, statistical analysis, mixtures optimization, experimental design. Resumo Na produção de revestimentos cerâmicos para parede e piso, são usadas misturas com matérias-primas de diversas regiões com características físicas e químicas diferentes. Essas mudanças de matérias-primas alteram as qualidades do produto final, o que implica em constante reformulação na composição de massas cerâmicas através de tentativas e erros, consumindo tempo e material. Isso configura a circunstância ideal para aplicar as técnicas de projeto de experimentos, freqüentemente usadas em outras áreas

This article presents a method to optimize the formulation of ceramic masses for coatings using the statistical design of experiments. The project of simplex mixtures in pseudocomponents considered six control factors (wt. %): talc, quartz, limestone, phyllite, dolomite and clay and three response variables: linear retraction, bending resistance and water absorption. The proposed method was implemented in the stages: (1) identification of the problem, (2) planning and execution of the experiments and (3) optimization and discussion of the results. The optimization method is defined through the simulation, imposing the restrictions that each response demands.

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