Summary
Add 2D-Cam with a Translating Flat-faced Cam-Follower
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 - it is Rocker [a Rocker that rotates continuously is usually called a 'Crank']. |
| • | The Cam-Follower slides - it is a Slider. |
|
Add geometry in the Base-Part to locate:
| • | the rotational centre of the Cam |
| • | the sliding axis of the Cam-Follower |
| STEP 1: | Add a new Mechanism-Editor |
| STEP 2: | Edit the Base-Part |
| STEP 3: | Add a Horizontal Line in the Base-Part. Its start-Point locates the centre of the Crank  [The Line's start-Point is for the Pin-Joint, and the horizontal Line is the 'solved' Line we need when we add the Motion-Dimension FB] |
| STEP 4: | Add a different Line to the Base-Part to locate to the sliding direction of the Slider  . The start-Point of the Line will be the 'solved' Point we need when we add the Motion-Dimension FB. |
| 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:
| • | offset from a radial axis from the centre of the Cam-Shaft 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 'overturning moment', which is the force that tilts the sliding-Part in its slide-way.
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 7: | Add a Crank . A Part with a Pin-Joint, and a Motion-Dimension FB to give the rotational angle of the Cam-Shaft. |
| STEP 8: | Add a Slider . A Part with a Slide-Joint, and a Motion-Dimension FB to give the linear position of the Cam-Follower.. |
| STEP 9: | Add the Linear-Motion and Motion FB, and connect the wires to the two Motion-Dimension FBs. |
Step 9 is complete
|
|
| STEP 10: | Edit a Motion for the Slider - about 30mm stroke. |
|
|
Add the sketch-loop to the Slider for the Cam-Follower
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 that the long-side are a different angle relative to the Cam-follower's motion.
|
| 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 :
- or -
Step 5 is complete.
|
|
Add the 2D-Cam
MechDesigner always calculates an external and an internal cam. For a Flat-Faced Follower, we must hide the external cam.
|
You can use the:
- or -
-or -
| 1. | Right-click the graphic area |
| 2. | Click Add 2D-Cam in the contextual-menu. |
When Add 2D-Cam is active [the cursor is 'Add 2D-Cam']:
| 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.
We must hide the 'outside' cam.
We can hide the 'outside' cam with the Cam Properties and Display dialog-box.
To edit the 2D-Cam
| 1. | Move your mouse-pointer over the 2D-Cam so that it becomes red. |
The 2D-Cam Properties and Display dialog-box opens.
|
|
In the 2D-Cam Properties and display dialog:
Cam Display tab: Cam Visibilities separator
| 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.
|
|
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.
|
|
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 of the flat-faced follower to one side of the Slider |
or
| • | Move the Slider's Axis so that it is not radial [on a ray] from the cam center. |
On this occasion I have made the Cam-Follower longer.
|
|
