Key Larnings:

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.


First: What do we want the Cam to look like?

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<<<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:

MD-QST5D-3-0

This 2D-CamRed-14-1b will looks like the Rocker motion.

We will look at four methods to add the 2D-Cam. We will explain the problems and advantages of each.

Method 1:
Method 3: Success for Single-axis Machines
Method 4: Success for Multi-axis Machines

tog_minusMethod 1: Add the 2D-Cam (as you would normally)

Icon-AddProfile

A Cam-Roller is a Profile element.

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STEP 1: Click Solids toolbar > Add Profile
STEP 2: Click the Circle in the Rocker Part | Click OK-tiny-11-15 in the Command-Manager.

There are two terms that we use.

Cam-Roller : the Profile that is in contact with the Cam.
Cam-Follower : the Part to which we add the Cam-Roller

Icon-Add2DCam

STEP 3: Click Kinematic FB toolbar > Add 2D-Cam

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We must click two elements:

STEP 4: Click the Base-Part
STEP 5: Click the Cam-Roller

Click OK-tiny-11-15 in the Command-Manager to add the 2D-Cam.

The Cam does not have 2 × Ramps!

 

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We can view the Pitch-Circle-Path:

STEP 6: Edit the 2D-Cam.
STEP 7: 2D-Cam dialog-box: Display tab > Cam Visibilities > Click Pitch-Curve check-box,  Clear Cam 1 and Cam 2 check-boxes.

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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.

 

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.

tog_minusMethod 2: 'Motion' from MMA as input to the Slider

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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STEP 1: Delete the wire that is at the input to the SLIDER Motion-Dimension FB
STEP 2: Connect the Linear-Motion FB directly to the Slider Motion-Dimension FB.

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

STEP 3: Click Kinematics FB toolbar > Add Gearing FB and the graphic-area.
STEP 4: Delete the wire that is from the Linear Motion FB to the Motion-Dimension FB (Slider)
STEP 5: Connect a wireRed-14-1b from the Linear-Motion FB to the Gearing FB and then a wireRed-14-2 to the Slider Motion-Dimension FB.

 

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STEP 6: Edit the Gearing FB
STEP 7: Gearing FB dialog-box: Gearing as Real or Ratio > Gearing as Ratio : Input-Pulley=90 / Output-Pulley=360

 

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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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STEP 8: Edit the radius of the Cam-Roller to R7mm
STEP 9: Edit the length of the rotating lever that is the Cam-Follower to 40mm

 

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.

tog_minusMethod 3: Connect the Slider the Rocker

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.

STEP 1: Delete all of the wires
STEP 2: Connect a wire from a Linear-Motion FB to the Slider Motion FB

Its output is, of course, the Slider motion that we have designed in MotionDesigner ( a Range of 0-100)

STEP 3: Connect a wire from the Slider Motion FB to the Slider Motion-Dimension FB

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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STEP 1: Connect the output from the Slider Motion-Dimension FB to the input of the Rocker Motion FB.

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.


STEP 2: Connect the output from the Rocker Motion FB to the input of the Rocker Motion-Dimension FB

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.

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.

STEP 1: Add a Gearing FB.
STEP 2: Connect a wireRed-14-1b from the Slider Motion-Dimension FB to the Gearing FB.
STEP 3: Connect a wireRed-14-2 from the Gearing FB to the 2 × Ramps Motion FB.
STEP 4: Edit the Gearing FB to open the Gearing FB dialog-box.
STEP 5: Gearing FB dialog-box > Gearing as Ratio : Input Pulley =360 : Output Pulley=100

The range of values at the output-connector of the Gearing FB is now 360

However, ...

The Output from the Slider Motion-Dimension FB 30 – 130, (as the Base-Value = 30mm).
The Minimum Output from the Gearing FB:
When the input to the Gearing FB is 30, its output is 30 * 360/100 = 108
When the input to the Gearing FB is 130, its output is 130 *360/100 = 468.
The input to the 2 × Ramps Motion FB is 108 - 468, not from 0 - 360.
It needs to be 0–360, not 108–468.

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

When the input to the Gearing FB is 30, its output is (30 * 360/100)-180 = 0
When the input to the Gearing FB is 130, its output is (130 *360/100)-108 = 360.
The input to the 2 × Ramps Motion FB is 0 - 360

Add Before Gearing Ratio

This parameter is added before the input is multiplied by the Gearing-Ratio

Thus if we enter the -30

When the input to the Gearing FB is 30, its output is (30-30) × 360/100 = 0
When the input to the Gearing FB is 130, its output is (130-30) ×360/100-108 = 360.
The input to the 2 × Ramps Motion FB is 0 - 360

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.


 

tog_minusMethod 4: Edit the Rocker Motion 'X Range'

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.

Xold

Xnew=30+(X1*100/360)

Y

0

30

0

30

38.333

0

110

60.555

10

140

60.888

10

230

93.888

20

360

130

20

The Slider-Cam and the Slot-Cam will now be the same as Method 3.

Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd