Abstract:

ESDU 92014 gives methods for designing blended cam profiles meeting the criteria that the maximum pressure angle does not exceed a specified value and that profile undercutting is avoided. Each rise or return motion segment is formed by blending components of two single-law segments at the point of maximum follower velocity. Either a hand calculation method may be used, with the graphical data of ESDU 92005, or the computer program (ESDUpac A9214). Both methods apply to six commonly used cam laws. The input is the chosen pressure angle, roller diameter, and blending ratio; also two out of segment angle, reference circle radius and follower lift are input and the optimum value of the third is found. The advantages increase with blending ratio and unblended segment angle but incur a decreased minimum profile convex radius of curvature and increased peak acceleration away from the cam. The program allows a set of blending ratio values to be explored and, once a suitable value has been chosen, the program can be run in another mode to give full details of the cam profile and the follower motion. The theoretical background is fully explained, step-by-step design procedures are provided, and the input to and the output from the program are illustrated with fully worked examples. ESDU 83027 is complementary and presents an alternative hand calculation method of blending applicable to cams driving either translating or swinging arm followers.