TABLE OF CONTENTS The previous chapter discussed a number of cam functions that proved to be dynamically unacceptable. This chapter will describe a set of functions that behave in an acceptable manner at moderate to high speeds for double-dwell applications, i.e., any rise or fall that lies between dwells. The variables used in this chapter are the same as those defined in Table 2-1 (p. 18). Note that in the form presented, with ? (in radians) as the independent variable, and constant cam angular velocity, the units of the expressions in equations for s, v, a, j are length, length/rad, length/rad 2, and length/rad 3 respectively. To convert these equations to a time base, multiply velocity v by the camshaft angular velocity ? (in rad/sec), acceleration a by ? 2, and jerk j by ? 3.
The bad examples of cam design described in the previous chapter should lead the cam designer to the conclusion that consideration of only the displacement function when designing a cam is erroneous. The better approach is to start with consideration of the higher derivatives, especially acceleration. The acceleration function, and to a lesser extent the jerk function, should be the principal concern of the designer. In some cases, when there is a specification on velocity, the velocity function must be carefully designed as well.
With this in mind, we will redesign the cam for the same example specifications as...
