﻿ 6A2.1: Translating Flat-faced Follower

# 6A2.1: Translating Flat-faced Follower

### Summary

This tutorial is Add Cam with an Translating Flat-faced Cam-Follower

#### Add the cam-Part and the cam-follower-Part

The cam and the cam-follower Parts usually belong to two different kinematic-chains.

In this tutorial, the kinematic-chains are very simple.

 • The cam Part rotates - it is a continuously rotating Crank.
 • The cam-follower Part slides - it is a Slider.

Add geometry in the Base-Part to define:

 • the centre-Point of the cam-Part
 • the direction of the cam-follower's motion.
 STEP 1: Add a new Mechanism-Editor
 STEP 2: Edit the Base-Part
 STEP 3: Add a Line in the Base-Part, to give the centre of the Crank  [The Line give a Point for the Pin Joint, and the Line for the Motion-Dimension FB]
 STEP 4: Add a Line in the Base-Part for the Slider
 STEP 5: Add dimensions and constraints to the Line sketch-elements

In the image, you can see that Line for the Slider is not vertical or horizontal, or on a radial axis from the Crank centre-Point .

In this case the Line for the Slider is:

 • at an angle of 50º
 • offset from a radial axis by 10mm.

The offset will not change the cam. It only moves the contact point to the left or the right of the sliding axis. Thus it will change the force that tilts the follower part.

Note: the short line that is perpendicular [⊥] to the Slider Line. The short Line is to dimension the distance from the centre-Point of the Crank-axis to the start-Point of the slider-axis. The dimension is 100.00 in the image.

 STEP 6: Close the Part-Editor.
 STEP 9: Add the Linear-Motion and Motion FB, and connect the wires.

Step 9 is complete

 STEP 10: Edit a Motion for the Slider - about 30mm stroke.

We must make a sketch-loop for the cam-follower. Clearly, for a flat-faced follower, one of the sketch-elements must be a Line. I have found the best shape for the flat-faced-follower is a long-narrow rectangle. One long side becomes the contact surface.

The long sides of the rectangle  are most frequently perpendicular [⊥] to the direction of the cam-follower's motion. However, it is possible to make the long-side at an angle to the motion.

### Add the sketch-loop to the Slider for the Cam-Follower

 STEP 1: Add a 'Line' that will be in contact with the cam.
 • Add the Line so its mid-point is approximately at the sliding axis of the Slider
 • You may need to edit the length of line later.
 • The Line can also be at a small angle relative to the direction of the Slider's Motion. In this case it 10º (90-80) from perpendicular [⊥].
 STEP 2: Complete a long narrow rectangle -  with a short Line that is perpendicular [⊥] to Line
 STEP 3: Complete the sketch with dimensions and constraints.

Step 3 is complete.

Make sure the rectangle is a 'sketch-loop'.

 STEP 4: Exit the Part-Editor
 STEP 5: Add a Profile to the sketch-loop rectangle

To add the Profile, use :

 1 Solid Toolbar > Add Profile

- or -

Step 5 is complete.

MechDesigner always calculates an external and an internal cam. Thus, we must hide the external cam.

You can use the:

 1 Mechanism Local Toolbar > Add 2D-Cam

- or -

-or -

 1 Right-click the graphic area

 1 Click the Crank
 2 Click the Profile - the long, narrow rectangle.

Finally, to end the Add 2D-Cam command:

 3 Click OK in the Command Manager

- or -

 4 Right-click the graphic-area

You can see in the image, that there are two Cam-Profiles.

Cam 1 and Cam 2 are in contact with the two long sides of the Flat-Faced Cam-Follower.

Generally, you will need one Flat-Faced Cam. Thus, we must hide the 'outside' cam.

We can hide one of the cams with the Cam Properties and Display dialog-box.

 STEP 2: Edit the 2D-Cam

To edit the 2D-Cam

 1 Move your mouse pointer over the 2D-Cam so that it becomes red.
 2 Double-click the cam.

The 2D-Cam Properties and Display dialog-box opens.

In the 2D-Cam Properties and display dialog:

 STEP 3: Click the Cam1 (or Cam2) to hide one of the Cams

Note:

In the Cam Properties and Display dialog-box it is also possible to show the 'Pitch-Curve'

The Pitch-Curve has no meaning with Flat-faced Followers.

Are there 'flats' on the cam?

If a 'flat' appears on the cam, then it probable that the cam needs to move beyond the end of the cam-follower face.

You must edit the one or all of these parameters

 • motion - so the Slider does not need to move as far or move as quickly. This may not be an option of course.
 • make the flat-faced follower longer
 • move the Slider nearer to the centre of the Crank (but be careful of undercutting)
 • offset the rectangle to one side of the Slider

or

 • Move the Slider axis so that it is not on a radius from the cam canter.

On this occasion I have made the Cam-Follower longer.

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