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

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= L 12 1 2 where L = 35˚, = 140˚, and = 220˚140˚= 80˚. For 220˚ 260˚ = 35˚ For the first part of the return, 260˚ 310˚, and = L 12 2 where L = 35˚, = 260˚, and = 360˚260˚=100˚ For the second part of the return, 310˚ 360˚, and = 2L 1 2 where L = 35˚, = 260˚, and = 360˚260˚=100˚ The displacement diagram is given below followed by a table of values for at 20˚ increments of . Theta Follower Angle 0.000 0.000 20.000 0.000 40.000 0.000 60.000 0.000 80.000 0.000 100.000 0.000 120.000 0.000 140.000 0.000 160.000 4.375 180.000 17.500 200.000 30.625 220.000 35.000 240.000 35.000 260.000 35.000 280.000 32.200 300.000 23.800 - 368 -
320.000 11.200 340.000 2.800 360.000 0.000 To lay out the cam, first draw the prime circle which has a radius of 2.0" + 1.0" = 3.0". Next draw the pivot circle for the follower pivot. The radius of the pivot circle is 4". Draw the follower in the initial position ( = 0˚ ) to determine the follower length (r 3 ) and the position on the pivot circle corresponding to = 0˚ . As indicated in Example 8.5, the length r 3 is given by r3 = r 1 2 (rb +r0) = 4 2 (2 +1) 2 = 2.646" Identify the point on the pivot circle corresponding to = 0˚ , lay off the radial lines at 20˚ increments from this point, and label the lines in the counterclockwise direction. Draw lines from the intersections of the radal lines with the pivot circle tangent to the prime circle. Then lay off the angular displacements from these tangent lines. Locate the center of the follower by the distance r 3 from the pivot circle along these lines. Draw 1" radius circles through the endponts of the distances layed off along these lines, and fit a smooth curve which is tangent to the circles corresponding to the roller follower. The cam profile is shown in the following figure. - 369 -
Page 1 and 2: Follower Travel, mm Displacement, c
Page 3: 220˚ 240˚ 260˚ 280˚ 1 inch 300

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

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