Geometric Analysis: Cam Size
Contents
Cam Size
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 (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 |
Disadvantages of a 'smaller' Cam.
A small cam:
| • | reduces the flywheel effect. This helps to rotate the cam-shaft at constant angular velocity. However, this effect is usually quite small. |
| • | increases the accuracy required to manufacture. |
| • | increases pressure angle and reduces the radius of curvature , which increases Hertzian Contact-Stress. |
Cam Size and the Measurement-Dimension FB
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To measure the Cam with a Measurement FB, we will click different Points. If necessary, to select Points only, use Filter menu > Filter Points. Basic Circle The radius of the Base-Circle is the minimum radius from the centre of the cam to the contact between the cam and the cam-follower.
The Measurement (and the FB) 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. You can also use a Stats FB to find the maximum and minimum values. Prime-Circle (also called the Reference Circle) The radius of the Prime-Circle is the minimum radius from the centre of the cam to the centre of the cam-follower.
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