Quality assessment of machining the main bearings journals of camshafts to oversize dimensions using statistical process control tools

High-quality repair and regular maintenance of the camshaft ensure reliable and efficient engine operation. The quality of restored parts depends on precision machining. The research aimed to evaluate the quality of equipment settings to machine the main bearing journals of the YaMZ-236 engine camshaft to oversize dimensions. To assess the quality of the camshaft restoration process, the authors applied control sheets, Shewhart control charts, and a histogram. The diameters of 20 camshaft bearing journals, both before and after repair, were determined in two cross-sections and in two mutually perpendicular planes using an SR-75 lever gauge. The check sheets allowed for the collection and processing of primary data for the statistical analysis of the repair of the YaMZ-236 engine camshaft. Analysis of the control charts showed that the variations in ranges (spreads) within and between the shafts are due to random causes. This indicates the stability and controllability of the technological process. The histogram allowed for the estimation of the probability of repairable defects at less than 0.5%, and irreparable defects (scrap) at 0%. The calculated reproducibility index of 1.66 shows that the technological process complies with the requirements. The quality of the machine settings for machining the bearing journals complies with the requirements. The study has confirmed a hypothesis regarding maintaining the machining quality through the regular application of statistical control methods.

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