Analysis of mechanical errors in disc cam mechanisms

Abstract

This paper presents an analytical method for analysing the mechanical errors of disc cam mechanisms. With the aid of parametric expressions of the cam profile and by employing the concept of equivalent linkage, the error of the follower motion that is due to the variation in each design parameter can be determined analytically. The resulting error equations do not really involve the location of the curvature centre of the cam profile, and thus locating the curvature centre of the cam profile is not essential. The method is validated through analysing a cam mechanism that has an invariant equivalent linkage, and thus an exact solution is available. Compared with the exact solutions, the predicted results have at least four-figure accuracy. For the roller follower cases, the pressure angle has most effect on the resulting error. Owing to the counteraction of the shift angle, the resulting error due to the radial dimension error of the cam profile has relatively smaller variation. In the worst case, owing to the combined effects of various design parameters, the accuracy of the follower motion may degrade considerably. The acceleration error functions have a sudden change at the ends of the motion.

A Convenient and Inexpensive Quality Control Method for Examining the Accuracy of Conjugate Cam Profiles

“…The difference between the variable center distance f * (that is between the cam and follower pivots) and its ideally constant distance f may be induced by the radial-dimension errors of cams A and B, Δr A and Δr B , the roller-radius errors of rollers C and D, Δr fC and Δr fD , the errors of the arm lengths, Δl A and Δl B , and the subtending angle error of the follower arms, Δη. As a special case of the mechanical error analysis of disk cam mechanisms (Wu and Chang, 2005;Chang and Wu, 2006), by employing the concept of equivalent six-bar linkage of this assembled conjugate cam mechanism, as shown in Fig. 4 in which, the correlations of θ 5 = α A and θ 6 = α B exist as shown in Fig.…”

“…By applying this concept, Chang et al (2009) have presented a rapid indirect method for examining profile deviations of conjugate disk cams. In their work, an analytical approach called conjugate variation analysis (or conjugate condition analysis), based on the mechanical error analysis of disk cam mechanisms (Wu and Chang, 2005;Chang and Wu, 2006), has been developed for relating the center distance variation with the profile deviations of a pair of conjugate disk cams. Then, conservative criteria for qualify control of assembled conjugate cams with the measurement of the center distance variation have been proposed and an experimental verification had also been conducted.…”

Tolerance analysis and synthesis of cam-modulated linkages

“…A variety of analytical or numerical approaches have been presented for the tolerance analysis of various types of cam mechanisms [12][13][14][19][20][21][22][23][24][25] or for that of linkages [15,16,[26][27][28][29]. Some of these approaches are further extended for the tolerance synthesis tasks with optimization models being established [12][13][14][23][24][25][26][27][28][29].…”

“…Therefore, establishing a more appropriate optimization model for the tolerance synthesis of cam-modulated linkages is still a matter of concern until now. The present paper, employing the concepts of equivalent linkage [15,19,20] and DFMA, demonstrates comprehensive and systematic mathematical tools for analyzing and synthesizing the tolerances in cam-modulated linkages. A practical case study of analyzing and synthesizing the tolerances in a cam-modulated linkage type pick-and-place device is then performed to illustrate the presented approaches.…”

Calculating actual profiles of conjugate disk cams by means of conjugate variation measurement

“…By applying this concept, Chang and Wu [11] have presented a simplified method for indirectly examining profile deviations of conjugate disk cams. In their work, an analytical approach called conjugate variation analysis (or conjugate condition analysis), based on the mechanical error analysis of disk cam mechanisms [12][13][14], has been developed for relating the subtending angle variation with the profile deviations of a pair of conjugate disk cams. Then, conservative criteria for qualify control of assembled conjugate cams with the measurement of the subtending angle variation have been proposed and an experimental verification had also been conducted.…”