Terminology that relates to 'Cam-Size'.
•Base Circle: the diameter of the smallest circle that is tangent to the cam surface.
•Prime Circle: the diameter of the smallest circle that is tangent to the Pitch-Curve.
•Cam Lift (also called Follower Stroke): the difference between the Prime-Circle and the maximum radius of the Pitch-Curve.
Advantages of a 'smaller' Cam.
A small cam:
•requires less space
•reduces material costs (however, a 'very' small and 'very' large cam increase manufacturing costs)
•reduces its inertia for rapid starting and emergency stopping
•reduces out-of-balance forces
•reduces the number-of-rotations that cam-follower roller makes for each rotation of the cam
•reduces the angular velocity and angular acceleration of the cam-follower roller
Disadvantages of a 'smaller' Cam.
A small cam:
•reduces the flywheel effect. A Flywheel helps to rotate the cam-shaft with a constant angular velocity
•increases the accuracy required to manufacture
To measure the Cam with a Measurement FB, we will click different Points.
Top-tip: To select Points only, use Filter menu > Filter Points.
Top-tip: Remember to turn Filter-Points OFF after you ave selected the Points !
The radius of the Base-Circle is the minimum radius from the center of the cam to the contact between the cam and the cam-follower.
1.Click Add menu (or Kinematic FB toolbar) > Measurement FB
2.Click the small Point at the contact between the Cam-Follower and the Cam
3.Click the Point at the center of the rotating Cam
4.Click the graphic-area.
The Measurement (and the FB) are now in the graphic-area . The Measurement will increase and decrease when you rotate the cam.
When the Measurement is a minimum - you have found the radius of the Base-Circle
The difference between the minimum and maximum values given by the Measurement FB is the Cam-Lift.
You can also use a Stats FB to find the maximum and minimum measurement values.
Prime-Circle (also called the Reference Circle)
The radius of the Prime-Circle is the minimum radius from the center of the cam to the center of the cam-follower.
1.Click Add Measurement FB
2.Click the Point at the center of the Cam and then the center of the Cam-Follower.