Hopefully, we will learn an important concept.
The motion of the Rocker is a function of the motion of the Slider.
We will add the Cam to the Base-Part . The Cam-Roller in the Rocker moves with the Slider over the Cam.
Note: Alternatively, in Step 6D1.2, it was possible to join the Rocker to the Base-Part, and move the Cam with the Slider. However, we joined the Rocker to the Slider.
<<<This is the motion we prepared for the Rocker in Step 6D1.2 The motion has 2 × Ramps IMPORTANT NOTE: Imagine the X-axis Units are mm and NOT degrees. Then it is easy to imagine that the X-axis is equal to the motion of the Slider. Let's look ahead: |
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This 2D-Cam We will look at four methods to add the 2D-Cam. We will explain the problems and advantages of each.
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A Cam-Roller is a Profile element. |
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There are two terms that we use.
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We must click two elements:
Click The Cam does not have 2 × Ramps!
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We can view the Pitch-Circle-Path:
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The Function-Blocks have been connected as: MMA(0-360) > Motion-FB(0-90) > Slider MMA(0-360) > Motion-FB(2 × Ramps) > Rocker Hence, the input to Motion FB (2 × Ramps) is 0 to 360 and thus its output is identical to the Motion Design in MotionDesigner.
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IMPORTANT CONCEPT If we delete the wire from the input to the Motion-Dimension FB for the Slider, the Slider will not move - obviously. However, the Rocker continues to do its motion. This is because the input to the Motion-Dimension FB for the Rocker has an input from the Linear-Motion FB (MMA) and the Motion FB (2 × Ramps). However, the Rocker should not move if the Slider does not move. |
This method will move the Slider at Constant-Velocity. Thus, the input to the Slider is equal to the input of the Rocker Motion FB. The output from the Linear-Motion FB is constant-velocity. The output from the Rocker Motion FB is now 2 x Ramps, while the Slider moves steadily, |
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As the input to the Slider is now 0 -360, the Slider will move 30mm (Base-Value) to 390mm (Base-Value + Motion-Value) with Constant-Velocity. It then instantly moves to 30mm after each 0-360 cycle of the MMA. |
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However, the motion-design of the Slider has a motion-range (as intended) of 90mm to move the Slider from 30mm to 120mm. To reduce the output from the Linear-Motion FB from 360 to 100mm, we can use a Gearing FB
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When look at Cam 1 and Cam 2 - and not only the Pitch-Circle, there is serious undercutting of the Cam.
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Now the stationary cam has 2 × Ramps is as we intend it to be. Excellent. ... However, ... |
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Question 2: Why is it not an excellent result? Answer 2: The Slider Cam looks like a 'Snail'! The Slider moves at constant-velocity in one direction, and then jumps back to zero. It does not have the motion-design Slider that is in MotionDesigner.
We want the 2D-Cam for the Slider AND the Stationary 2D-Cams. <<< Click the image to expand and collapse. |
As stated above. We want a Cam to rotate the Rocker and also a Cam to move the Slider. |
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We will add all of the wires again.
Its output is, of course, the Slider motion that we have designed in MotionDesigner ( a Range of 0-100)
Its output controls the Slider Part - which will move by the BASE-Value(30) + Motion Values . ( a Range of 30-130) This is the normal way to connect a Motion-Part.
This is the IMPORTANT STEP! |
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The input to the Rocker Motion FB now has a motion-range from 30 -100. This is equal to the X-axis of the motion in the Rocker name-tab in MotionDesigner. The image to the left indicates the input range, or the X-axis motion-values, on the Motion graph, which is at the input to the Rocker Motion FB The motion-values (30 to 130) increase from 30 to 130 and then decrease again from 130 to 30 - exactly as does the Slider motion. The output motion-values from the Motion FB have a range of 0 to 10 - the Y-AXIS of the motion in the Rocker motion name-tab.
The input to the Rocker Motion-Dimension FB is 0 to 10(Y-axis of Rocker motion). To find the angle of the Cam-Roller relative to the X-axis, we simply need to add up these values. The Motion-Dimension is relative to the vertical line in the Slider Part =+90°, the Motion-Dimension FB > Base-Value = +230°, the Line for the Cam-Roller in the Rocker Part is at +30° .Thus +90+230+30 =350° or -10° Thus, the Motion-Range, relative to the X-axis, rotates the Cam-Roller from -10 to 0. |
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Note: You will get a message in the Feedback area: '1 Mechanism dependencies detected'. It is advisable to rebuild the model when the number of dependencies becomes more than 1. The Slot-Cam looks near to complete. However: it is not complete? The motion-values at the input (the X-axis) to the Rocker Motion FB have a motion-range = 30 - 130. We want the motion-range at the input (X-axis) of the Rocker Motion FB to be 0 to 360. Thus, we need to move the starting point of the input(X-axis) from 30 to 0, and the maximum value to 360, but still be a function of the output from the Slider Motion-Dimension FB |
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We can use a Gearing FB.
The range of values at the output-connector of the Gearing FB is now 360 |
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However, ...
To correct this offset we can use one of two possible other parameters in the Gearing FB. |
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Add After Gearing Ratio This parameter is added after the input is multiplied by the Gearing-Ratio Thus if we enter the -108
Add Before Gearing Ratio This parameter is added before the input is multiplied by the Gearing-Ratio Thus if we enter the -30
Thus, we get the same result in the two cases. <<< The Gearing FB parameters. |
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We can see that the Slot-Cam now has the correct-profile. |
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We do NOT need to design the motion for the Rocker with an X-axis motion-range of 360. We can design the Rocker motion with an X-axis motion-range of 100. Also, we can start the Motion at 30 and not 0. |
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The new Motion Table is as follows. The Y-axis is the same.
The Slider-Cam and the Slot-Cam will now be the same as Method 3. |