HIGH-PRECISION CAM MANDRELS

The article is concerned with cam mandrels used for positioning of asymmetrical blanks such as rings and bushings while machining. It is understood that blanks have high bending stiffness. There is GOST 31.1066.04–97, developed for cam mandrels, but according to manufacturers and scientists, the design proposed in GOST has a number of drawbacks, which can be attributed to simplified technology of mandrel parts manufacture. This has been proven by practical experience. The paper points out the defects of standard cam mandrel design and describes a fragment of the process for manufacture of more accurate mandrels. While designing cam mandrel it is necessary to provide for safe attachment of blanks (this requirement is well addressed), to know the influence of main parameters of its parts on the machining accuracy and to prevent damage to base surface of the blank. Practically, the last two requirements are not addressed. A series of articles, including this paper, covers theoretical and experimental studies to meet these requirements. Six prototype mandrels with different number of cams (from three to twelve), model rings and six batches of ring blanks are designed and manufactured for experimental and production-related studies of accuracy of positioning and machining of blanks in cam mandrels. The model rings and blanks in the batches have different diameter of the base hole and its length in order to study these parameters for accuracy of positioning and machining of blanks. In each batch there are at least 30 blanks which makes it possible to process the results obtained in the experiments by mathematical statistics methods. Four batches of blanks have polished base holes, and two batches have turned holes. The model rings and blanks have been subjected to metrological control.