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 .|
|•||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 smaller cam:
|•||reduces material costs (but 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|
|•||reduces the sliding distance the flat-faced follower makes for each rotation of the cam, thus reducing wear|
|•||reduces the sliding velocity with flat-faced follower, thus reducing wear |
Disadvantages of a 'smaller' Cam.
A smaller cam:
|•||reduces the flywheel effect. This helps to rotate the cam-shaft at constant angular velocity. |
|•||increases the accuracy required of a CNC machine tool to manufacture|
Cam Size and the Measurement-Dimension FB
Measurement of the Base Circle, Prime Circle, Cam Lift
To measure the Cam, use a Measurement FB.
Basic Circle [See image: Base-Circle = 80mm]
You may need to 'Filter Points' so that you only can click Points.
|2.||Click the small Point at the contact between the Cam-Follower and the Cam|
|3.||Click the Point at the centre of the rotating Cam|
|4.||Click the graphic-area.|
The Measurement-Dimension in the graphic-area continually updates as you cycle the model.
Look at the Measurement-Dimension in the graphic-area to find the minimum measurement - the Base-Circle Radius - in the image it is 80mm - or use a Graph FB to plot the radius.
The difference between the minimum and maximum values of the Measurement-Dimension is the Cam-Lift.
You can also use a Stats FB to find the maximum and minimum values.
Prime-Circle (also called the Reference Circle) [See image: Prime-Circle = 100mm]
The Prime-Circle Radius is the minimum diameter from the centre of the cam to the centre of the Cam-Follower.
|1.||Click Add Measurement FB |
|2.||Click the Point at the centre of the Cam and then the centre of the Cam-Follower.|