Advanced Engineering Drawing
Constructing A Cam Profile
Simple Harmonic Motion
This is a method describing the procedure to draw the displacement diagram for simple harmonic motion.
Assume that a roller follower is to rise 1 1/2" in a uniform motion in 180 degrees and fall 1 1/2" in the same
motion in 180 degrees. The rotation of the cam is counterclockwise. The diameter of the base circle is 3
1/2" and the diameter of the roller follower is 1/2".
Drawing the Cam Displacement Diagram:
1. Lay off the base line of the displacement diagram equal to the circumference of the base
2. Lay off the height of the displacement diagram equal to the maximum rise of the follower (1
1/2"). Dimension this height.
3. Divide the base line of the displacement diagram into twelve equal parts, each division
representing 30 degrees of cam rotation. Draw vertical lines through these points to
complete the displacement diagram. Label the divisions from zero degrees to 360 degrees.
4. Construct a semicircle on one end of the displacement diagram. The diameter of the
semicircle is equal to the distance of the rise of the follower. Divide the circle into six equal
parts, each part representing 30 degrees of the cam motion.
5. Project the points on the divided semicircle across the displacement diagram using
6. Use an irregular curve to construct a smooth curve through the intersections of the horizontal
and vertical lines. The displacement diagram describing the cam motion is completed. Add
a title to the displacement diagram to complete the drawing.
Constructing the Cam Profile:
1. Construct the base circle including centerlines.
2. Draw radial line spaced every 30 degrees. Label these lines in a clockwise direction. The
rotation direction is given in the problem. The labels should correspond to the degree numbers
on the displacement diagram.
3. Transfer the distances for each degree interval from the displacement diagram to the radial lines.
The distances are measured from the base line of the displacement diagram to the graphed cam
4. Draw a smooth curve through the intersection on the radial lines to complete the cam profile.
Finished Cam Drawing:
1. Darken in the cam profile. Show the radial lines as dimension lines for dimensioning a
radius and then show the dimension of the distance from the center of the base circle to
the cam profile and the degree number. Draw the shaft and the key and add the
2. Draw and dimension the cam follower. Be sure to show the minimum and maximum
position of the follower. Dimension this distance.
3. Indicate the rotation direction.
4. Draw the side view of the complete cam, shaft, key, and follower.