No one is sure where or how cams got their start. The Sanskrit (Indo-Iranian) term “Jambha” (cog, peg, or tooth) may indicate the geographic area in which they had their beginnings. So may the Teutonic “Kambr” (toothed instrument). Suffice it to say that they have been with us for some time. Excellent compilation of practical cam mechanisms is given by Jones and Grodzinski.
The method of combining basic curves was employed to obtain desired displacement, velocity, and acceleration curves .The utilization of polynomial equations directly to find the necessary curve shapes are used now .These equations are compiled by Stoddart.
Now numerical procedures are considered for establishing the follower characteristic curves by utilizing incremental tabulated values. These values may be estimated, taken from the actual cam shape measurements, or calculated from an analytical cam curve. This method of finite differences is excellently applied by Johnson.
The polydyne cam combines the polynomial equation with the dynamics of the follower system; the result is an excellent approach to a high-speed, highly flexible system .The poltdyne method was originally presented by
Turkish in his excellent article verified that the jump occurs when the response curve falls below the spring curve by his tests. The jump becomes more predominant with smaller values of λ or with more flexible systems .A direct approach for establishing the minimum allowable value of λ to prevent jump is done by Karman and Biot.
A critical survey of intermittent-motion mechanisms was presented by Lichtwitz.Various computer aided softwares are even designed for drawing the cam profiles.
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