Step 13.5: Cam Speed and Cam-Follower Force

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Step 13.5: Cam Speed and Cam-Follower Force

Cam Speed and the Cam-Follower Contact Force.

The Cam-Follower (Rocker/Lever) and the Cam-Follower Roller have mass. As you increase the machine speed, you will also increase acceleration and inertia forces.


In this step,

1.We will give the Cam-Follower a Motion - from MotionDesigner.

2.We increase the machine speed until the Contact-Force between the Cam and Cam-Follower becomes zero or negative.

Add a Motion to the Cam-Follower.

GST-T13.5-MotionP5N5

This motion will rotate the Cam-Follower by ±5º – rotate a total of angle of 10º.

Use the tools in MotionDesigner to design the motion to the left.

 

GST-T13-5-A-CamMotion

1.Add a Motion FB to the graphic-area .

2.Edit the Motion FB . In the Select Motion  drop-down box, select Motion1.

3.Connect the Linear-Motion FBRed-14-1b to the Motion FBRed-14-2 and to the Motion-Dimension FBRed-14-3 for the Cam-Follower.

I have de-selected Show Force Vectors to make it easier to see the new shape of the 2D-Cam.

See, in the image:

The 2D-CamRed-14-4

The original Cam Profile element (Pink)Red-14-5.

Cam Contact Force

There are four methods to show the Contact-Force between a 2D-Cam and Cam-Follower.

Note :

With all four methods, you must Configure the Power Source to make sure the 2D-Cam is the Power-Source for the Cam-Follower.

See Configure Power Source

GST-T13-3-CamDouble-Click

Methods 1: Show Force Vectors to show the

Force-Vector that ACTS-ON the Cam-Follower Part

Force-Vector that ACTS-ON the Cam-Part

YOU must determine whether the contact-force is active ON (towards) the 2D-Cam or active OFF (away from) the 2D-Cam.

Method 2: 2D-Cam > Cam Display Options > Contact-Force.

Method 3: Force-Data FB and plot with a Graph FB.

YOU must determine whether the contact-force is active ON (towards) the 2D-Cam or active OFF (away from) the 2D-Cam.

Method 4: Use a Cam-Data FB. connect the Contact Force output to a Graph FB.

If the Contact Force ≤ Zero(0), then the Contact-Force is = Zero(0).

Method 4 is usually the most informative.

GST-T13-3-Cam-ContactForce

We will use Method 2: 2D-Cam dialog-box.

1.Double-click the 2D-Cam

The 2D-Cam dialog-box opens.

We want to show the contact force

In the Cam Display Options separator, select

Contact Force

To see the colors more clearly, make the:

Line Thickness: = 2 or 3

GST-T13-3-Cam-ContactForce-B

In the graphic-area, the 2D-Cam shows the:

Cam is color Coded

Contact-Force at the contact point

Color-coded swatch and Force scale at the left of the display

Note:

The Cam and Cam-Roller distort slightly under the Contact-Force, and Contact-Stress, between the Cam and Cam-Follower.

If the Cam-Follower is Cylindrical OR Flat, the contact is across the width (±Z-axis) of the Cam-follower. The contact is rectangular.

If the shape of the Cam-Follower is a Barrel, the contact is elliptical. Barrel-shaped Cam-Followers are available from most manufacturers of Cam-Followers.

If the shape of the Cam-Follower is Spherical, the contact is a circular.

GST-T13-3-Cam-ContactForce-C

Drag the Master-Machine-Angle Slider until the Contact-Force is at a minimum.

For my motion, the Master-Machine-Angle is 110º.

The minimum Contact-Force is at the same Master-Machine-Angle, approximately, as the X-axis of the Motion, which is the maximum deceleration of the Cam-Follower Arm.

GST-T13-3-Cam-ContactForce-D

Do Edit menu > Machine Settings dialog

Increase the Machine-Speed (Cycles / Min (RPM)) until the Contact-Force becomes is approximately 0N.

Again, drag the Master-Machine-Angle Slider until the Contact-Force is at a minimum. If the contact-force is a function of inertia, gravity, and springs, then the minimum will be at different machine-angles for different machine-speeds.


For my motion, the Contact-Force becomes ~0N when the cam-shaft rotates at ~111 Cycles / minute. (RPM)

The maximum speed is a function of:

The motion

The mass and mass distribution of the Cam-Follower Rocker

Are there ways to increase the speed of the cam-shaft, but use the same motion and the same mass distribution?