A plate cam with a radial reciprocating roller follower is to be designed using the input, the rise and fall, and the output motion shown in Table P6.28. The base circle diameter is 3 in and the diameter of the roller is 1 in. Displacements are specified as follows:

Table P6.28 Displacement information for plate cam with reciprocating roller follower.

Input Θ

(deg)

Lift L

(in) Output y 0◦−90◦ 3.0 Cycloidal rise 90◦−105◦ 0 Dwell 105◦−195◦ −3.0 Cycloidal fall 195◦−210◦ 0 Dwell 210◦−270◦ 2.0 Simple harmonic rise 270◦−285◦ 0 Dwell 285◦−345◦ −2.0 Simple harmonic fall 345◦−360◦ 0 Dwell Plot the lift curve (displacement diagram) and the profile of the cam.

(a) Comment on the lift curves at appropriate positions of the cam (for example, when the cam rotation angle is Θ = 0◦, Θ = 45◦,

Θ = 180◦, Θ = 210◦, Θ = 225◦, and Θ = 300◦).

(b) Identify on your cam profile the location(s) and the value(s) of the largest pressure angle. Would this pressure angle cause difficulties for a practical cam-and-follower system?

(c) Identify on your cam profile the location(s) of any discontinuities in position, velocity, acceleration, and/or jerk. Are these discontinuities acceptable (why or why not)?

(d) Identify on your cam profile any regions of positive radius of curvature of the cam profile. Are these regions acceptable (why or why not)? (e)

For the values given in Table P6.28, what design changes would you suggest to improve this cam design?