Evaluation of the production process in natural stone plants by quality charts

Quality can be defined as the degree to which features related to a product or service meet the specified or possible needs. The quality level of a product is the desired characteristics and the level of satisfaction for that product. Quality control is required in order to obtain the desired quality product. Quality control is applied not only to the product but also to the control of the production process. In the process control, the control process is carried on throughout the production and the factors that can cause poor quality production are determined and eliminated in advance, so the necessary corrections are made in the process before the defective final product is formed. Thus, it is ensured that the production process is secured in such a way that it does not produce imperfect production. Marble and natural stone production process, the most important factors affecting the product sales price, the dimensions of the plates and plates produced, colors and patterns, structural defects and surface brightness. For this reason, the quality control and selection sections of marble processing plants have thickness, width, and brightness controls. In this study, the usability of quality control charts was investigated in the selection departments of marble processing plants. For this purpose, changes in thickness and brighness values that are important in marble production were investigated, and control charts were prepared and analyzed in three different methods, which are Shewhart, CUSUM and EWMA. The study was conducted on three different types of marble and 50 samples were used for each type, 6 for each thickness and 9 for brightness data, and total 2250 data were studied. Lastly, the data were evaluated according to TS EN 1469 (2006), TS EN 1468 (2012), TS EN 12058 (2007), TS EN 12057 (2007) and TS EN 1343 (2013) and compared with the results obtained from the control graphs. When the data evacuated; According to X-S graphs of Denizli travertine thickness values, it was observed that 31 of X and S of 18 were outside the confidence interval. 40 of the CUSUM graphics and 33 of the EWMA graphics are outside the confidence interval. For the brightness values, 24 for X and 4 for S were observed to be out of control. The CUSUM and EWMA results are also very close to one with 34 and 30 samples. In the grey Imperial work, the values of thickness in X-S graphics are 5 examples of those outside the range of confidence. In the cusum graph, there are 12 samples and 19 samples in EWMA. 23 and 5, CUSUM 20 for X-S graphics for brightness, and 27 EWMA are out of the range of sample trust. In the Italian grey study, the results of the control charts of the thickness values were shown as follows: x graph 11, s graph 9 CUSUM graph 7, and EWMA 17 samples were out of control. For brightness results, there were 28 in X, 4 in S, 27 in CUSUM, 36 in EWMA. According to TS EN 1468-1469-12058, 15 of Denizli travertine samples, 2 of gray emprador samples and 3 of Italian gray samples are out of thickness standards. According to TS EN 12057, sample quantities are 20-31 for Denizli travertine, 7-23% for gray emprador and 6-14 for Italian gray. As a result; Denizli travertine was found to be the most uncontrolled samples in the evaluation of both thickness and brightness measurements. In gray emprador and Italian gray samples, uncontrolled data were found to be glossier. In addition, it is understood that there is a linear relationship between thickness and brightness of the number of non-control samples for Denizli travertine. In the light of this information, it was concluded that Denizli travertine samples had problems in both sizing and polishing processes due to the fact that they were very hollow, while the other samples contained various minerals and the errors were mostly realized in the polishing stage.