6A2.1: Translating-Flat-Faced Follower

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6A2.1: Translating-Flat-Faced Follower

Summary

Add Cam-Part and the Cam-Follower Part, and specify their motions.

Add a sketch-loop to define the shape of the Flat-Face Cam-Profile.

Add the 2D-Cam

Add the Parts for the Cam and Cam-Follower

In this tutorial, the two Parts - Cam and Cam-Follower - are in two simple kinematic-chains.

The Cam rotates continuously - in the Kinematics-Tree it is defined as a Rocker . When a Rocker that rotates continuously is also called a Crank).

The Cam-Follower Slides - it is a Slider.

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STEP 1: Add two Lines to the Base-Part to locate:

the rotational-center of the Cam-Shaft

the sliding-axis of the Cam-Follower

1.Add a new Mechanism-Editor

2.Edit the Base-Part

3.Part-Editor: Geometry toolbar > Add Line. Its start-PointRed-14-1b locates the center of the Cam-Shaft

4.Part-Editor: Constraints toolbar > Add Horizontal Click the Line

5.Part-Editor: Constraints toolbar > Add Coincident. Click the Y-axis then the start-Point of the Line, then again, click the X-axis and the start-Point of the Line

6.Part-Editor: Geometry toolbar > Add LineRed-14-2. Its position and axis locates the sliding-axis of the Cam-Follower.

7.Part-Editor: Geometry toolbar > Add Dimension: Add the dimensions as indicated in the image to the left

8.Exit the Part-Editor

Note: To add the perpendicular distance from the start-Point of LineRed-14-2 to the start-Point of LineRed-14-1b you will need to add LineRed-14-3 that is perpendicular to LineRed-14-2.

In the image, you can see that the sliding-axis of the Cam-FollowerRed-14-2 is not vertical or horizontal, or on a radial axis from the rotating-axis of the Cam-Shaft Red-14-1b.

The offset will not change the cam. However, it moves the contact point to the left or the right of the sliding axis. Thus, it will change the 'overturning moment', which is the force that tilts the sliding-Part in its slide-way.

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STEP 2: Add the Cam-Shaft Motion-Part.

1.Mechanism-Editor: Kinematic-elements toolbar > Add Part:  Click and drag to add the Part

2.Mechanism-Editor: Kinematic-elements toolbar > Add Pin-Joint | Click the start-Point of the new Part and the start-Point of the Horizontal Line in the Base-Part.

3.Mechanism-Editor: Kinematic-FB toolbar > Add Motion-Dimension FB : Click the Pin-Joint, click the Horizontal Line in the Base-Part, and click the CAD-Line in the Cam-Shaft Part.

4.Mechanism-Editor: Kinematic-FB toolbar > Add Linear-Motion- FB : Click the FB and then the graphic-area.

5.Mechanism-Editor: Connect a wire from the Linear-Motion-FB to the Motion-Dimension FB.

STEP 3: Add the Cam-Follower Motion-Part.

1.Mechanism-Editor: Kinematic-elements toolbar > Add Part:  Click and drag to add the Part

2.Mechanism-Editor: Kinematic-elements toolbar > Add Slide-Joint | Click the CAD-Line along the new Part and the Line in the Base-Part, that will be the sliding-axis of the Cam-Follower.

3.Mechanism-Editor: Kinematic-FB toolbar > Add Motion-Dimension FB : Click the Slide-Joint, click the start-Point of the sliding-axis of the Line in the Base-Part, and the start-Point of the Cam-Follower Part

4.Mechanism-Editor: Kinematic-FB toolbar > Add Linear-Motion- FB : Click the FB and then the graphic-area.

5.Mechanism-Editor: Kinematic-FB toolbar > Add Motion : Click the FB and then the graphic-area.

6.Mechanism-Editor: Connect the wires from the Linear-Motion-FB to the Motion FB and to the Motion-Dimension FB.

 

STEP 4: Edit a Motion for the Slider - about 30mm stroke.

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

When a circular shape is in continuous contact with the cam we call it a Cam-Roller Follower. When the shape in contact with the Cam is a Line we call it a Flat-Faced Follower.

In all cases, the shape to be in continuous contact with the cam must be a sketch-loop. For a flat-faced follower, one of the sketch-elements must be a Line.

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1.Add the long-faced follower shape to the Slider.

1.Add a LineRed-14-1b that will be in contact with the cam.

Add the Line so its mid-point is 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 (⊥).

2.Add three more lines to complete a long narrow rectangle -  with a short LineRed-14-2 that is perpendicular (⊥) to LineRed-14-1b

3.Complete the sketch-loop as a rectangle and add dimensions and constraints.

4.Exit the Part-Editor


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STEP 5: Add a Profile to the sketch-loop

To add the Profile, do:

1. Click Solid toolbar > Add Profile  

2.Click the long rectangle as the sketch-loop

 

 

Add the 2D-Cam

MechDesigner always calculates an external and an internal cam. For a Flat-Faced Follower, we must hide the external cam.

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STEP 1: Add a 2D-Cam

1.Machine-elements toolbar > Add 2D-Cam

2.Mechanism-Editor: Click the CrankRed-14-1b

3.Mechanism-Editor: Click the ProfileRed-14-2 - the long, narrow rectangle.

4.Click OK-tiny-11-15 in the Command-Manager

- or -

4.Right-click the graphic-area

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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.

We must hide the 'outside' cam.

We can hide the 'outside' cam with the Cam dialog-box.

STEP 2: Edit the 2D-Cam

To edit the 2D-Cam

1.Move your mouse-pointer over the 2D-Cam

2.Double-click the cam.

Or See How to open a dialog-box

Dialog-R13.2-CamDisplay-CamVisibilities

In the :

To hide the outside cam -

1.Click 2D-Cam dialog-box > Cam Display tab: Cam Visibilities  > Click Cam1 (or Cam2) check-box

Note:

In the 2D-Cam dialog-box it is also possible to show the Pitch-Curve

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

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Trouble-shooting

Does the Cam make contact with the Flat-Faced Follower for the complete rotation of the cam?

Are there 'flats' on the cam?

If a 'flat' appears on the camRed-14-1b, then you must edit the model - see below.

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You must edit the one or all of these parameters

Motion-Design for the Slider - Can the Slider move more slowly, or not as far. This may not be an option of course.

Edit the flat-faced follower shape so that it is longer

Move the Slider axis nearer to the axis of the Cam-Shaft (but be careful of undercutting)

Offset the Flat-faced follower (rectangle) to one side of the Slider

On this occasion I have made the Flat-Faced Follower longer.