Why use a Motion-Dimension Function-Block?

Each Motion-Dimension FB identifies a Motion-Part.

A Motion-Dimension FB can specify the:

Angle between Lines in two separate Parts. This is a Rocker.

- or -

Distance between Points in two separate Parts. This is a Slider.

There are two components to the motion of the Motion-Part. Its:

start-position, called the Base-Value, which we edit with the Motion-Dimension FB dialog-box
motion-values, which we specify at its input-connector.

The Motion-Dimension FB equation is:

Output motion-value = Base-Value + input motion-values


Use the Motion-Dimension FB dialog-box to edit the Base-Value parameter.

Motion-Dimension FB

Add Motion-Dimension FB

Kinematic FB toolbar > Motion-Dimension FB [right of Graphic-Area >>]

Menu:

Add menu > Add Motion-Dimension FB

GA-FB-MotDim-Design-Set

In the graphic-area: Motion-Dimension FB if the parameter is an element-row in a Design-Set.

How to Add:

The Motion-Dimension FB is the most complex FB to add to the model.

It is easy when you can identify the three elements that you must select.

See below : Videos


Add Motion-Dimension FB to become a Rocker: [see more details here]

1.Click Add menu > Add Motion-Dimension Function-Block (FB)

You must click three elements to complete the command. The selection-boxes are in the Command-Manager.

2.Click Element #1 : Pin-Joint
3.Click Element #2 : Line in a kinematically-defined Part.
4.Click Element #3 : Line in a Free-Part.
5.Click OK to in the Command-Manager

The two Lines must radiate from the Points that also specify the Pin-Joint [Element #1]- see Note 1 and 'Special-Procedures'

Icon-FB-MotionDimension-Rocker--inGA

In the graphic-area: Motion-Dimension FB for a Rocker

Add Motion-Dimension FB to become a Slider [see more details here]

1.Click Add menu > Add Motion-Dimension Function-Block (FB)

You must click three elements to complete the command. The selection-boxes are in the Command-Manager.

2.Click Element #1 : Slide-Joint
3.Click Element #2: Point in a kinematically-defined Part.
4.Click Element #3 : Point in a Free-Part

The two Points must be at an end of each of the two Lines that also specify the Slide-Joint [Element #1]- see Note 2 and 'Special-Procedures'

Icon-FB-MotionDimension-Slider-inGA

In the graphic-area: Motion-Dimension FB for a Slider

Note 1: When Element #1 is a Pin-Joint ...

A Pin-Joint has been added with Point 1 and Point 2, at the ends of Line 1 and Line 2.

The two Lines you must select to complete the command must radiate from the Pin-Joint and the Reference-Elements of the Pin-Joints are also Reference-Elements of the Lines

Elements #2 & #3 must be:

Element #2: is Line 1 that is a child to a kinematically-defined Part
Element #3: is Line 2 that is a child to a Free Part

Note 2: When Element #1 is a Slide-Joint ...

The Slide-Joint has previously been added with Line 1 and Line 2.

There is a Point at the end of each Lines 1 & 2.

Elements #2 & #3 must be:

Element #2: is a Point at the end of a Line in a kinematically-defined Part and in the Slide-Joint .
Element #3: is a Point at the end of a Line in a Free Part and in the Slide-Joint.

Note: In the graphic-area:

Use CTRL+Drag to move the Motion-Dimension's dimension and arrowhead.
Use Drag to move the Motion-Dimension FB icon.

See Also:

Connecting FBs

Videos:

Add a Motion-Dimension FB to a Pin-Joint – General Procedure

 

 

Add a Motion-Dimension FB to a Slide-Joint

 

 

 

Full Description

Note: Styling : Charcoal, Dark, Edit menu > Application-Settings > Graphics tab > Display Colours :  [Background : White] ;  [Part-Unsolved : Blue] ; [Part-Solved: Green] ;[ Joint-Solved : Green] ; [Joint-Unsolved : Blue]

tog_minusElement #1: Pin-Joint – General Procedure

Add Motion-Dimension FB

Kinematic FB toolbar > Motion-Dimension FB [right of Graphic-Area >>]

CM-AddMotionDim-A

When you start Add Motion-Dimension FB, the Command-Manager needs you to select three elements to complete the command.

The selection-box hints are:

1.Element #1: Joint [Pin or Slide]

Elements 2 and 3 are in two different Parts.

2.Element 2#: Select Solved Line or Point [green]* [this is termed also as 'a Line in a Part that is kinematically-defined Part]
3.Element 3#: Select Unsolved Line or Point [blue]* [this is termed also as 'a Line in a Part that is not kinematically-defined]

The Elements #2&#3 must also construct the joint that you select as the Element #1

GA-AddMotionDimRock-0

Preparation:

1.Lines4s5s that are in two different Parts1s-red2s
One Part is a kinematically-defined Part (Green Part-Outline)...in this case it is the Base-Part1s-red
The other Part2s is a Free Part (Blue Part-Outline)2s
2.The two Parts are joined with a Pin-Joint3s
3.Lines4s5s radiate from the Pin-Joint3s

It is also important that the Points that were selected to assemble the Pin-Joint3s are at the ends of Lines4s5s.

GA-AddMotionDimRock-1

Select the First Element: PIN-JOINT3s

When you select a Pin-Joint, the second and third elements must be Lines.

One Line is a 'Solved' Line [solved Line = within a Part that has a Green Part-Outline and kinematically-defined Part].
The other is 'Free Line [Free Line = within a Part that has a Blue Part-Outline]

This means the Pin-Joint must join a Free Part to a kinematically-defined Part.

GA-AddMotionDimRock-2

Select the Second and Third Elements: LINES 4s5s

The Lines that you select as the second and third elements are 'parents' to the Points that specify the Pin-Joint.

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

GA-AddMotionDimRock3

Result: The Motion-Dimension FB is added to define the rotation angle of a Rocker.

The dimension2s is an Orange colour in the graphic-area.

Icon-FB-MotionDimension-Rocker--inGA

--- the icon in the graphic-area for a Rocker1s-red [Dark Grey Background colour]

KT-Rocker

Kinematics-Tree for a Rocker

When we add a Motion-Dimension FB to a Pin-Joint, we identify it as a Rocker in the Kinematics-Tree.

The kinematic elements that construct the Rocker are:

'Part' + 'Pin-Joint' + 'Motion-Dimension' = 'Rocker'

tog_minusSlide-Joint - General Procedure

GA-AddMotDim-Slider-0

Preparation:

1.Two Parts1s-red2s
2.One is a kinematically-defined Part (Green Part-Outline)...the Base-Part1s-red
3.The other is a Free-Part (Blue Part-Outline)2s
4.The Two Parts are Joined... with a Slide-Joint3s

Note the Points4s5s are in the Lines that were selected for the Slide-Joint3s

CM-AddMotionDimension-Slider1

Select the First Element: SLIDE-JOINT3s

When you select a Slide-Joint, the second and third elements are Points.

One Point is a 'Solved' Point
The other Point is 'Free' Point

Each Point must be a child to the Lines that were used for the Slide-Joint.

Hence, the Slide-Joint should join a kinematically-defined Part and a Free Part.

CM-AddMotionDimension-Slider3

Select the Second and Third Elements: POINTS 4s5s

The second4s and third5s elements are children to the Points to the the Lines used for the Slide-Joint.

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

GA-AddMotDim-Slider-1

Result: The Motion-Dimension FB is added to define the linear distance of a Slider

You can see the dimension is a Gold colour.

Icon-FB-MotionDimension-Slider-inGA

The icon in the graphic-area for a Slider [Dark Grey Background colour]

KT-Slider

Kinematics-Tree

When we add a Motion-Dimension FB to a Slide-Joint, we identify it as a Slider in the Kinematics-Tree.

'Part' + 'Slide-Joint' + 'Motion-Dimension' = 'Slider'

Special Procedures

two or more Coincident Pin-Joints

When there are two or more coincident Pin-Joints, and three or more Lines radiate from the same location, you must take care when you select the Pin-Joint as the first element.

The second and third elements you select can only be Lines that are parents to Points and the Pin-Joint you select as the first element.

two or more Coincident Slide-Joints

When there are two or more coincident Slide-Joints, and three or more Lines are along the same 'ray', you must take care when you select the Slide-Joint as the first element.

The second and third elements you select can only be the Points that are children to the Lines to the Slide-Joint you select as the first element.

See Special Condition below.

See Add Pin-Joint - Special Condition and Add Slide-Joint - Special Condition

SPECIAL PROCEDURES: Coincident Pin-Joints

Frequently in a machine, there are a number of Rotating-Parts that rotate about one Point.

If you want to specify the motion of each rotating part, with a different Motion-Dimension FB, you must carefully select the Points when you add the Pin-Joints,

Then, when you add the Motion-Dimension FBs, the Motion-Dimensions can reference the correct Parts.

SPECIAL PROCEDURE 1:

MD-MotionDimension-sc11

At the end of Special Procedure 1:

Two Motion-Dimension FBs to reference the same Line in the Base-Part.

You can see the angle dimension of the two Motion-Dimensions FBs start at the horizontal Line.

tog_minus        STEP 1: Add Pin-Joints two times

MD-MotionDimension-sc1

There are two Parts and a Line to the Base-Part - three Parts in total.

The Points at the ends of the lines are 5, 7 and 11.

MD-MotionDimension-sc2a

In the image to the left, we have joined Point7 to Point5 with the first Pin-Joint.

Now we must add a second Pin-Joint.

PROCEDURE 1

We will add the second Pin-Joint between Point11 and Point5.

Q: Why Point5 and not Point7?

A: Point5 is a child to the horizontal Line1s-red .
We want two Motion-Dimensions to reference the same horizontal Line1s-red .

md-motiondimension-sc3

To add the Pin-Joint: select Point11 and then try to select Point5.

Because Point5 and Point7 are at the same position, MechDesigner does not know which Point you want to select.

There is ambiguity between Point5 and Point7. Hence, the Select Elements dialog-box opens.


The Select Elements dialog-box:

Gives ALL of the elements to complete the command are available
The element you had selected first is at the top of the list.
None of the elements are selected.

CTRL +Click ALL of the elements you need to complete the command.

md-motiondimension-sc4

Here, we have selected Point 11 and Point5

1.CTRL + CLICK Point11 AND Point5
2.Click 'OK'

tog_minus        STEP 2: Add Motion-Dimension FB two times

MD-MotionDimension-sc5

The two Parts are now joined to the Base-Part with two Pin-Joints

Now, use the Motion-Dimension FB two times

 

1.Click Function-Block toolbar > Add Motion-Dimension FB.

CM-AddMotionDim-A

We must click the three elements: 1s-red, 2s and 3s.

Select Elements dialog box

Elements 11s-red:

2.Click a Pin-Joint.

There are two Pin-Joints that are at the same position.

Hence, MechDesigner opens the 'Select Elements' dialog-box.

Select the first Pin-Joint 1s-red , at the top of the list.

MD-MotionDimension-sc7

Elements 2 & 3: Two Lines – a 'Solved Line' 2s then a 'Free Line' 3s

3.Click the horizontal Line 2s
4.Click the CAD-Line 3s along one of the Parts

MD-MotionDimension-sc9

This image shows the three elements in the Command-Manager boxes.

MD-MotionDimension-sc8a

The first Rocker Motion-Dimension FB.

Now, add the second Motion-Dimension FB

We must now select another three elements,4s5s6s

MD-MotionDimension-sc10

Select Function-Block Toolbar > Motion-Dimension FB in the  again.

These are the elements.

1.Joint: Pin-Joint24s.

Now, there is not ambiguity. There is only one Pin-Joint available.

2.Line – Solved5s: select the horizontal Line.
3.Line – Free6s: select the CAD-Line along the center of the Blue Part.

MD-MotionDimension-sc11

Here, you can see the result.

Both Motion-Dimensions FBs use the Horizontal Line that is a child to the Base-Part as a reference for the motion-dimension.

Note: When you add two Motion-Dimensions, the FBs may be on top of each other.

Drag each FB so you can see them.

SPECIAL PROCEDURE 2:

MD-MotionDimension-sc14

At the end of Special Procedure 2

We want the two Motion-Dimensions FB as:

Motion-Dimension 1: From the horizontal Line in the Base-Part to a Line in 'Part 1'
Motion-Dimension 2: From the Line in 'Part 1' to the Line in 'Part 2'

 

tog_minus        STEP 1: Add Pin-Joint two times

MD-MotionDimension-sc1

Again, there are two Parts and a Line in the Base-Part.

The Points at the ends of the lines are 5, 7 and 11.

We want to:

Add a Pin-Joint between 'Point7' and 'Point5', and
Add a Pin-Joint between 'Point11' and 'Point7'.

MD-MotionDimension-sc2

In the image to the left, Point7 is joined to Point5

CONDITION 2

Add the second Pin-Joint between Point11 to Point7.

Q: Why Point7 and not Point5
A:  Because Point7 is a child to CAD-Line1s-red and we want this Motion-Dimension to reference CAD-Line1s-red.
We do not want the Motion-Dimension to reference the Line in the Base-Part. That was Procedure 1, above.

Select Elements Dialog box

Select Point11.

Then try to select Point7

There is ambiguity between Point5 and Point7. Hence, the Select Elements dialog-box opens.

ALL the elements you need for the command are made available to you
The first element you select is at the top of the list.

Select Elements dialog box

In the image to the left, we have selected Point11 and Point7.

1.CTRL + CLICK Point11 AND Point7
2.Click 'OK'

tog_minus        STEP 2: Add Motion-Dimension FB two times.

MD-MotionDimension-sc5

The two Parts become joined with a Pin-Joint.

 

To add two Motion-Dimension FBs, use Add Motion-Dimension FB two times.

 

The Add Motion-Dimension FB requires three elements.

Select Elements dialog box

Element 1: A Joint.

There is ambiguity when we select the Pin-Joint, hence the Select Elements dialog-box opens.

Here, I have selected the first Pin-Joint 1s-red at the top of the list.

Then, Click 'OK'.

MD-MotionDimension-sc7

Elements 2 & 3: Two Lines – a Solved Line 2s then a Free Line 3s

There are three Lines to select from.

Select the Horizontal Line 2s and the CAD-Line 3s along one of the Parts

MD-MotionDimension-sc9

The three elements in the Command-Manager

Click OK in the Command-Manager

MD-MotionDimension-sc8

You can see the First Motion-Dimension FB.

Add the second Motion-Dimension.

We must now select another three elements,4s5s6s

MD-MotionDimension-sc13

These are the elements:

1.Joint: when we select the Pin-Joint4, there is no ambiguity because the existing Motion-Dimension FB uses the other Pin-Joint.

You must select this line because the Pin-Joint4 uses Point7 on this Line.

2.Line – Free: select the CAD-Line along the center of the Blue Part.

MD-MotionDimension-sc14

This image shows the end result.

First Motion-Dimensions FB: uses the Horizontal Line that is a child to the Base-Part as a reference Line.

Second Motion-Dimension FB: uses the CAD-Line along the center of the Added-Part that is kinematically-defined by virtue of the First Motion-Dimension FB - see Procedure 1

Note: When you add two Motion-Dimensions, the FBs may be on top of each other.

DRAG each FB so you can see them.

SPECIAL PROCEDURES: when there are coincident Slide-Joints

use the same concepts as for the Pin-Joint

tog_minus'Positive' Direction of Slide-Joints and Slider

Top-Tip : plan. Drag Lines, and Parts, from the 'start-Point' to the 'end-Point' in the same direction and in the positive direction of the Motion-Dimension.

The Positive-Direction of a Motion-Dimension for a Slider is logical, but needs some thought.


Always, the positive-direction of a Slider Motion-Dimension is:

'...the positive direction of the Line, or CAD-Line, that is kinematically-defined before you add the Motion-Dimension to the Slide-Joint'.


What is the Positive-Direction of a Line or CAD-Line?

The direction with which you drag - from its start-Point to its end-Point - when you add a new Line or new CAD-Line, and a new Part (its CAD-Line).


Example Sliders

Note:

Line 1 in each case is in the 'Fixed Green Part' – it belongs to a kinematically-defined part.
Line 2 the 'Free Blue Part' – it becomes a Slider after you add the Motion-Dimension FB, and a kinematically-defined part and a Motion-Part.

I have used the red arrow-heads to show the direction in which I 'dragged' to add the Lines and Parts

SJ-Dreiction11

Line 1 – Drag from Left to Right
Line 2 – Drag from Left to Right

The Motion-Dimension is '12.0000'.

Increasing the value, say to 16, will move the Motion-Part(Slider) to the right.

The small green arrowhead at the start-Point of Line 1 shows the positive direction of the Line and the Slider.

SJ-Dreiction12

Line 1 – Drag from Left to Right
Line 2 – Drag from Right to Left

The Motion-Dimension is '11'.

Increasing the value, say to 16, will move the Motion-Part(Slider) to the right.

The small arrowhead shows the positive direction

SJ-Dreiction22

Line 1 – Drag from Right to Left
Line 2 – Drag from Left to Right

The Motion-Dimension is -10'.

Increasing the value, say to -6, will move the Motion-Part(Slider) to the left.

The small arrowhead shows the positive direction

SJ-Dreiction21

Line 1 – Drag from Right to Left
Line 2 – Drag from Right to Left

The Motion-Dimension is -10'.

Increasing the value, say to -6, will move the Motion-Part(Slider) to the left.

The small arrowhead shows the positive direction

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd