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 smaller 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
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
increases pressure angle and reduces the radius of curvature [increases Hertzian Contact-Stress]

Cam Size and the Measurement-Dimension FB

Measurement of the Cam Base Circle, Prime Circle, Cam Lift

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.

1.Click Function-Block menu (or toolbar) > Add Measurement FB
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.

Cam Lift

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.

 

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd