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 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-centre of the Cam-Shaft |
| • | the sliding-axis of the Cam-Follower |
| 1. | Add a new Mechanism-Editor |
| 3. | Part-Editor: . Its start-Point locates the centre of the Cam-Shaft |
| 4. | Part-Editor: Click the Line |
| 5. | Part-Editor: 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:  . Its position and axis locates the sliding-axis of the Cam-Follower. |
| 7. | Part-Editor: : Add the dimensions as indicated in the image to the left |
Note: To add the perpendicular distance from the start-Point of Line to the start-Point of Line you will need to add Line that is perpendicular to Line.
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In the image, you can see that the sliding-axis of the Cam-Follower is not vertical or horizontal, or on a radial axis from the rotating-axis of the Cam-Shaft .
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: : Click and drag to add the Part |
| 2. | Mechanism-Editor: Click the start-Point of the new Part and the start-Point of the Horizontal Line in the Base-Part. |
| 3. | Mechanism-Editor: : 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: 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: : Click and drag to add the Part |
| 2. | Mechanism-Editor: 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: : 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: Click the FB and then the graphic-area. |
| 5. | Mechanism-Editor: 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 . 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 Line 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 Line that is perpendicular (⊥) to Line |
| 3. | Complete the sketch-loop as a rectangle and add dimensions and constraints. |
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| STEP 5: | Add a Profile to the sketch-loop |
To add the Profile, do:
| 2. | Click the long rectangle as the sketch-loop |
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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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| 2. | Mechanism-Editor: Click the Crank |
| 3. | Mechanism-Editor: Click the Profile - the long, narrow rectangle. |
| 4. | Click  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.
To edit the 2D-Cam
| 1. | Move your mouse-pointer over the 2D-Cam |
Or See How to open a dialog-box
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In the :
To hide the outside cam -
| 1. | Click 2D-Cam dialog-box > Cam Display tab: Cam Visibilities > Click (or ) 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 cam, 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.
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