Why use a Motion-Dimension Function-Block?

A Motion-Dimension FB specifies the start Position [Base-Value] of a Motion-Part.

The Motion-Part's motion is given by motion-values at the input-connector of the Motion-Dimension FB.

A Motion-Part is a Rocker or a Slider.


After you add Motion-Dimension FB, open the Motion-Dimension FB dialog-box to edit its parameters.

MD-32-FB-MTDIMA

Function-Block toolbar > Motion-Dimension Function-Block (FB)

Command:

Function-Block menu  > Add Motion-Dimension Function-Block (FB)

What for:

Each Motion-Dimension FB identifies a Part we want to move with a specified motion.

A Motion-Dimension FB can specify the:

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

- or -

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

The Rocker and Slider are Motion-Parts.

Symbols in the graphic-area:

MD-32-FB-PINMDA

Motion-Dimension FB for a Rocker

MD-32-FB-SLIMDA

Motion-Dimension FB for a Slider

FB-MotDim-DesignSet-icon

Motion-Dimension FB if its dimension is an element in a Design-Set.

How to Add:

Add to a Motion-Dimension FB:

1.Click Function-Block menu [or toolbar]  > 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, as the first element [Element #1], a Joint.

If you click a:

Pin-Joint: the second and third element must be Lines.
The two Lines must radiate from the Pin-Joint - see Note 1

or

Slide-Joint: the second and third element must be Points
Each Point must be from the two Lines that specify the Slide-Joint - see Note 2

Note 1: If Element #1 is a Pin-Joint...Elements #2 and #3 must be:

Lines that radiate from the same Pin-Joint that is Element #1

AND

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

Note 2: If Element #1 is a Slide-Joint....Elements #2 and #3 must be:

Points that are children to each Line in the Slide-Joint that is Element #1

AND

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

Special Notice:

1.To move the dimension in the graphic-area, you must use CTRL+ Drag the Dimension's Arrowhead

General Procedure

When you can click:

one Pin-Joint - see here

- or -

one Slide-Joint - see here

See also Videos


Special Procedure

When there are two or more coincident Pin-Joints or Slide-Joints so that two or more show in the Selection-Window with one mouse-click.

Coincident Pin-Joints

If there are two or more coincident Pin-Joints, and three or more Lines that radiate from the same location, then you must take care as to how you add the Pin-Joints and then 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.

Coincident Slide-Joints

If there are two or more coincident Slide-Joints, with three or more Lines that lie along the same ray, then you must take care how you add the Slide-Joint and then 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


Possible Messages:

If there is more than one Joint at the Pin-Joint you select as the 'first' element in the command manager, (a different Pin-Joint or a different Slide-Joint), and that Joint joins two kinematically-defined Parts, then you will get the message:

Joints: - Joint: X-Joint, it is not possible to add a Motion-Dimension FB to Green Parts.

If the Line you select as 'second' element is superimposed over another Line that does not radiate from the Joint, then you will get the message:

Line is not a child to the same Part as the Joint.

See Also:

Function-Block menu

Tutorial 6: Add and Connect Function-Blocks

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

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

 

 

tog_minusPin-Joint – General Procedure

MD-32-FB-MTDIMA

The Add Motion-Dimension FB is in the Function-Block Toolbar.

MotionDimension-CM1

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

1.A Joint1s-red
2.A sketch-element – solved2s*
3.A sketch-element – free3s* (notice a bug in the image!)

The two sketch-elements (solved and free) must assemble the Joint that you select for the Motion-Dimension.

*2s'Solved' is kinematically-defined, 3s'Free' is Not kinematically-defined.

FB-AngMotDim

Preparation: Add a Motion-Dimension to a Pin-Joint

1.Two Parts1s-red2s
oOne is a kinematically-defined Part (Green Part-Outline)...the Base-Part1s-red
oThe other is a Free Part (Blue Part-Outline)2s
2.The Two Parts are Joined... with a Pin-Joint3s
3.Lines4s5s that 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.

MotionDimension-CM1-PJ

Select the First Element: PIN-JOINT3s

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

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

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

MotionDimension-CM2-PJ

Select the Second and Third Elements: LINES 4s5s

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

MotionDimensionB

Result: The Motion-Dimension FB added to a Pin-Joint.

You can see the dimension2s is a Gold colour in the graphic-area.

MD-32-FB-PINMDA

--- the icon in the graphic-area for a Rocker1s-red

KT-Rocker2

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_minusPin-Joint – SPECIAL PROCEDURES: when there are 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

We want the two Motion-Dimensions to reference the same Line in the Base-Part.

 

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 Point 7 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'

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 Add Motion-Dimension FB in the Function-Block Toolbar.

MD-MotionDimension-sc5a

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 coincident Pin-Joints.

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

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 Add Motion-Dimension FB in the Function-Block Toolbar 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 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'

 

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 Point 11 and Point7.

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

MD-MotionDimension-sc5

The two Parts become joined with a Pin-Joint.

 

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

tog_minusSlide-Joint - General Procedure

MotionDimensionC

Preparation: Motion-Dimension to be added to a Slide-Joint

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 that  the Lines selected for the Slide-Joint3s

MotionDimension-CM1-SJ

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.

MotionDimension-CM2-SJ

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.

MotionDimensionD

The Motion-Dimension FB applied to a Slide-Joint.

You can see the dimension is a Gold colour.

MD-32-FB-SLIMDA

The icon in the graphic-area for a Slider

KT-Slider2

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'
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. Here, there are four.

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

Help Files for MechDesigner and MotionDesigner 11.1 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd