﻿ Getting Started Tutorials - MechDesigner > Tutorial 13: Forces: Introduction  > Step 13.5: Cam Speed and Cam-Follower Force

# 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.

 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. 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 FB to the Motion FB and to the Motion-Dimension FB 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-Cam •The original Cam Profile element (Pink).

#### 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. 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. 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 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. 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. 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?