Cam Size
Terminology
Term : |
Definition |
Base Circle : |
The diameter of the smallest circle that is tangent to the Cam-Profile. |
Prime-Circle : |
The diameter of the smallest circle that is tangent to the Pitch-Curve. |
Cam Lift (STROKE) : |
The difference between the Prime-Circle and the maximum radius of the Pitch-Curve. |
Advantages of a small Cam.
A small cam:
•decreases required space
•decreases manufacturing cost - however, an extremely small cam can also increase manufacturing costs
•decreases inertia to help rapid starting and emergency stopping
•decreases out-of-balance force (if the Cam is not balanced)
•decreases Follower-Roller RPM - assuming the same roller is used for the smaller cam.
Disadvantages of a small Cam.
A small cam:
•decreases the flywheel effect - a flywheel helps to rotate the cam-shaft with a constant angular velocity.
•may increase pressure angle and decrease the radius of curvature which will also increase Hertzian Contact-Stress.
Cam Size and the Measurement-Dimension FB
 Measuremnt FBs to measure the Base-Circle, Prime-Circle, and Cam-Lift. |
Use a Measurement FB to measure the basic dimensions of a Cam-Profile, 1.Click Kinematic FB toolbar > Measurement FB 2.Click Filters toolbar > Filter Points Basic Circle The minimum radius from the center of the Cam-Shaft to the contact between the Cam-Profile and the Follower-Roller. 3.Click the contact Point between the Follower-Roller and the Cam-Profile. 4.Click a Point at the center of the Cam-Shaft When the Measurement is a minimum - you have found the radius of the Base-Circle. Cam Lift The difference between the minimum and maximum values given by the Measurement FB is the Cam-Lift (also called its Stroke) Prime-Circle (also called the Reference Circle) The radius of the Prime-Circle is the minimum radius from the center of the Cam-Shaft to the center of the Follower-Roller. 1.Click a Point at the center of the Cam-Shaft and a Point at the center of the Follower-Roller. |