Why use a Motion-Dimension Function-Block?

A Motion-Dimension FB identifies a Motion-Part

A Motion-Dimension FB can specify the:

Angle of a Rocker

- or -

Distance of a Slider

Add Motion-Dimension FB

Add Motion-Dimension FB

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

Menu :

Add menu > Add Motion-Dimension FB

How to Add :

The elements you select to add a Rocker are different to those you select to add a Slider.

Select three elements for three selection-boxes in the Command-Manager in order:

Element #

Element type

Rules

#1

Pin-Joint

The Pin-Joint is between a Point in two different Parts:

One Part is a kinematically-defined Part, and
One Part a free Part
The Point in each Part must each define the end of a Line

The Line in each Part must radiate from the Pin-Joint.

#2

Line

The Line that radiates from the Pin-Joint
Is in the kinematically-defined Part

#3

Line

The Line that radiates from the Pin-Joint
Is in the free Part

To complete the command:

Click OK-tiny-13-17 in the Command-Manager

or

Right-click in the graphic-area [recommended]

Icon-FB-MotionDimension-Rocker--inGA

The Motion-Dimension FB for a Rocker in the graphic-area.

See more :

Details here


Select three elements for three selection-boxes in the Command-Manager in order:

Element #

Element type

Rules

#1

Slide-Joint

The Slide-Joint is between a Line in two different Parts

One Part is a kinematically-defined Part, and
One Part is a free Part

#2

Point

The start-Point or the end-Point of the Line that defines the Slide-Joint [Element #1], and
Is in the kinematically-defined Part

#3

Point

The start-Point or end-Point of the Line that defines the Slide-Joint [Element #1], and
Is in the free Part

To complete the command:

Click OK-tiny-13-17 in the Command-Manager

or

Right-click in the graphic-area [recommended]

Icon-FB-MotionDimension-Slider-inGA

The Motion-Dimension FB for a Slider in the graphic-area.

See more :

Here


Dialog box:

Motion-Dimension FB dialog-box

Notes:

After you add the Motion-Dimension FB, and you want to move the:

Motion-Dimension : CTRL+Drag the arrowhead of the dimension
Motion-Dimension FB icon : Drag the icon

GA-FB-MotDim-Design-Set

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

See also:

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

Selection Filters

Connecting FBs

Videos:


Motion-Dimension FB to a Pin-Joint

 


Motion-Dimension FB to a Slide-Joint

 

 


General Procedures

tog_minusMotion-Dimension FB and Rocker

Prepare the model so that these elements have these properties.

Element #

Element type

Rules

#1

Pin-Joint

of two Points, with a Point from one Line in two different Parts , and
one Part must be a kinematically-defined Part
the other Part must be a free Part

#2

Line

is a Line that radiates from the Point that specify the Pin-Joint [Element #1], and
in the kinematically-defined Part

#3

Line

is a Line that radiates from the Point that references the Pin-Joint [Element #1], and
is in the free Part

GA-AddMotionDimRock-0

Preparation example:

Pin-Joint3s
The Points at Pin-Joint3s are at the ends of Lines4s5s.
Lines4s5s in two different Parts1s-red2s that radiate from two Points
Part1s-red is a kinematically-defined Part (Green Part-Outline).
Part2s is a free Part (Blue Part-Outline)

Add Motion-Dimension FB

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

GA-AddMotionDimRock-1

Element #1: PIN-JOINT3s

The Pin-Joint is a joint between two Parts, and:

One Part is a kinematically-defined Part
One Part is a free Part

GA-AddMotionDimRock-2

Elements #2 and #3: LINES 4s5s

Each Line must be a child to a Point that is also a child to the Pin-Joint. [Element #1]

Element #2: a Line in the kinematically-defined Part
Element #3: a Line in the free Part

 

GA-AddMotionDimRock3

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

Result: a Rocker

A Motion-Dimension FB to specify the angle between Lines, Elements #2 and #3

The dimension1s is an Orange colour in the graphic-area.

Icon-FB-MotionDimension-Rocker--inGA

--- the icon2s in the graphic-area for a Rocker.

Note: The icon in this small image has a Dark Grey graphic-area

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 are:

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

tog_minusMotion-Dimension FB and Slider

Prepare the model so that these elements have these properties.

Element #

Element type

Rules

#1

Slide-Joint

of two Lines, one Line in each of two different Parts , and
one Part must be a kinematically-defined Part
the other Part must be a free Part

#2

Point

the start-Point or the end-Point of the Line that references the Slide-Joint [Element #1]
that is in the kinematically-defined Part

#3

Point

the start-Point or the end-Point of the free Line that references the Slide-Joint [Element #1]
that is in the free Part

GA-AddMotDim-Slider-0

Preparation example:

1.Two Parts1s-red2s

One is a kinematically-defined Part (Green Part-Outline)...the Base-Part1s-red

The other is a free Part (Blue Part-Outline)2s

2.The Parts are Joined... with a Slide-Joint3s

Note the Points4s5s are the start-Points and end-Points of the Lines that are selected for the Slide-Joint3s

Add Motion-Dimension FB

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

CM-AddMotionDimension-Slider1

Element #1: SLIDE-JOINT3s

The Slide-Joint is a joint between two Parts, and:

One Part is a kinematically-defined Part
One Part is a free Part

CM-AddMotionDimension-Slider3

Elements #2 and #3: POINTS 4s5s

Each Point must be a child to a Line that is also a child to the Slide-Joint. [Element #1]

Element #2: a Point that is a start-Point or end-Point of a Line in the kinematically-defined Part
Element #3: a Point that is a start-Point or end-Point of a Line in the free Part

 

GA-AddMotDim-Slider-1

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

Result: a Slider

The Motion-Dimension FB to specify the linear distance between Points, Elements #2 and #3

All Parts are now kinematically-defined Parts

The dimension1s is a Gold colour.

Icon-FB-MotionDimension-Slider-inGA

<<< the icon2s in the graphic-area for a Slider

Note: This small image has a Dark Grey graphic-area

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.

The kinematic elements are:

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

Special Procedures

Frequently, in a machine, there are coincident Joints. Two or more Rotating-Parts that rotate about one centre, or two or more Sliding-Parts that slide along one axis.

SPECIAL PROCEDURES: Coincident Pin-Joints

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

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

SPECIAL PROCEDURES: Coincident Slide-Joints

If you want to specify the motion of each sliding part with a different Motion-Dimension FB, you must carefully plan as to which Lines you select when you add the Slide-Joints,

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

The Lines you select when you add the Slide-Joint determine between which two Parts you can specify the Motion-Dimension FB.

In addition, to guarantee the Positive Direction of the Slide-Joint, you must be careful as to in which direction you add Lines and Parts.

See Positive Direction of Slider Motion-Dimensions.


SPECIAL PROCEDURE 1:

GA-MotDim-SpecialCase-11

Result of Special Procedure 1:

The model shows

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

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

tog_minusSTEP 1: Add Pin-Joints two times

GA-MotDim-SpecialCase-0

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

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

GA-MotDim-SpecialCase-1

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 .

GA-MotDim-SpecialCase-2

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.

GA-MotDim-SpecialCase-3b

Here, we have selected Point 11 and Point5

1.CTRL + CLICK Point11 AND Point5
2.Click OK-smallest

 

GA-MotDim-SpecialCase-4

 

The two Parts are now joined with a Pin-Joint to the Point at the left end of the Line in the Base-Part.

tog_minusSTEP 2: Add Motion-Dimension FB two times

GA-MotDim-SpecialCase-4

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.

GA-MotDim-SpecialCase-5a

The Command-Manager show that we must select three elements 1s-red, 2s and 3s.

 

The first-element must be a Pin-Joint or Slide-Joint.

We have two Pin-Joints!

GA-MotDim-SpecialCase-5

 

When we click the Pin-Joints in the graphic-area the Select-Elements dialog-box opens as there are two Pin-Joints.

In the Select-Elements dialog box:

Click the Pin-Joint5 - the one with the lower Element-Number if the names are different to those in the image.

GA-MotDim-SpecialCase-6

 

GA-MotDim-SpecialCase-7

Now we must select two Lines.

 

Click the horizontal Line 2s as the second element

Click the CAD-Line 3s along one the Parts with which the Pin-Joint is made.

GA-MotDim-SpecialCase-8

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

GA-MotDim-SpecialCase-9

The first Rocker Motion-Dimension FB.

Now, add the second Motion-Dimension FB

We must now select another three elements,4s5s6s

GA-MotDim-SpecialCase-10

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.

GA-MotDim-SpecialCase-11

Here, you can see the result.

Both Motion-Dimensions FBs use the Horizontal Line in 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

Result of Special Procedure 2

We want the two Motion-Dimensions FB:

Motion-Dimension 1:

From the 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_minusSTEP 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_minusSTEP 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-tiny-13-17 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.


tog_minusPositive' Direction of Slide-Joints and Slider

The nursery rhyme : She swallowed a cat, which swallowed a mouse, which swallowed a spider, which swallowed a fly... will come to mind.

A Slider:

When you add the Motion-Dimension FB, to add a Slider, you must select a Slide-Joint, as the first element, then two Points.

You might be surprised by how many elements properties we need to consider to understand and plan the Positive-Direction of the Motion-Dimension FB for a Slider:

The properties of the Motion-Dimension FB are determined by the properties of the Slide-Joint you select
The properties of the Slide-Joint are determined by the properties of the Lines you select to add the Slide-Joint.
The properties of the Lines are determined by the properties of the Points at each end of the Line : its start-Point and its end-Point:

Thus, the behaviour of the Motion-Dimension FB is a function of the order of the Points for each of the two Lines

Thus if the Motion-Dimension does not work in the way you want, you may need to add the Slide-Joint, and even the Lines again.

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 planning.


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 > Right
Line 2 – Drag from Left > 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 > Right
Line 2 – Drag from Right < 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 < Left
Line 2 – Drag from Left > 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