Pitch Circle Problem 8.17 Construct the profile of a disk cam that ...

220˚
240˚
260˚
280˚
1 inch
300˚
180˚
200˚
Prime circle
320˚
340˚
0˚
80˚
100˚
120˚
Problem 8.21
Lay out a cam profile assuming that an oscillating, roller follower starts from a dwell for 0˚ to 140˚
of cam rotation, and the cam rotates clockwise. The rise occurs with parabolic motion during the
cam rotation from 140˚ to 220˚. The follower then dwells for 40˚ of cam rotation, and the return
occurs with parabolic motion for the cam rotation from 260˚ to 360˚. The amplitude of the follower
rotation is 35˚, and the follower radius is 1 in. The base circle radius is 2 in, and the distance
between the cam axis and follower rotation axis is 4 in. Lay out the cam profile using 20˚ plotting
intervals such that the pressure angle is 0 when the follower is in the bottom dwell position.
Solution:
The displacement profile can be easily computed using the equations in Chapter 8 using a
spreadsheet or MATLAB program. Remember that the parabolic motion is represented by two
curves in each rise and return region. The curves are matched at the midpoints of the rise and
return. The profile equations are:
For 0 140˚
= 0
For the first part of the rise, 140˚ 180˚ , and
= 2L
2
where L = 35˚, = 140˚, and = 220˚140˚= 80˚.
For the second part of the rise, 180˚ 220˚ , and
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