Motion-Path FB

Summary of Motion-Path FB

Use the Motion-Path FB to add a point, we call a Motion-Point, to a sketch-path, which may crossed[8] or not crossed[0]. The Motion-Point is a kinematic element, which means we can join the end-Point of a Part to it with a Pin-Joint. We also know its motion-values.

The motion-values at the input-connector to the Motion-Path FB move the Motion-Point along the sketch-path. The units of the motion-values at the input are important.

When the motion-values at the input to the Motion-Path FB are:

Linear Units [mm]: 'Distance the Motion-Point moves along the Motion-Path = Input Motion-Value [mm]. To help you remember: 'Linear' = 'Literal' Distance.
Angular Units [degrees]: 'Distance the Motion-Point moves along the Motion-Path = Input Motion-Value [degrees] /360 To help you remember '360 degrees at input' = 1 cycle of the sketch-path'

Note: A Sketch-Path is: one to many sketch-elements joined end-to-end with Merged-Points ; Open[Γ] or Closed[Δ] ; crossed[α] or not crossed[ε].

Add and Edit Motion-Path FB



Kinematics FB toolbar > Motion-Path FB [right of Graphic-Area]


Add menu > Add Motion-Path FB


STEP 1: Add the Motion-Path FB to the graphic-area

1.Single-Click Kinematics FB Toolbar > Motion-Path FB

The Command-Manager starts. You must select a sketch-element.

2.Single-Click a sketch-element in the graphic-area.
3.Click OK-tiny-11-15 in the Command-Manager.

GA-Motion-Path FB2

A Motion-Path FB 1s-b is now in the graphic-area next to the start-Point of the sketch-element that you click.
A Motion-Point 2-R-RED-15 is coincident with the start of the sketch-element you click.


STEP 2: Open the Motion-Path FB dialog-box:

1.Double-click the Motion-Path FB in the graphic-area.

- or -

Motion-Path FB dialog-box

Motion-Path FB dialog-box [R13.2]

Motion-Path FB dialog-box [R13.2]

There are two tabs:

Point Parameters
Length Control
tog_minusPoint-Parameters tab


Point Parameters 

Note: if the input to the Motion-Path FB is a Linear-Motion-FB, which has a range of 360, then the Motion-Point will move along the complete sketch-path one time, and return to the start-Point of the sketch- at MMA=0 and REVS=1.

Number of Motion-Points:

Motion-Points are distributed equally distributed along the sketch-path.

Note: Click the Re-generate Motion-Points button [at the bottom of this separator] to update the Number of Motion-Points parameter.

If you have previously made Pin-Joints with Motion-Points, you must add the Pin-Joints again.

Range [360=complete path] [deg] / Linear Range [mm].  Default Range [deg] = 360, Default Linear Distance = Length of sketch-path*.

When the Number of Motion-Points parameter is two or more:

Range = 360[deg], or Linear Range = total length of sketch-path[mm]: the Motion-Points (as given in the # Motion-Points box) become equally spaced along the complete length of the Path.
Range ≠ 360 [deg], or Linear Range ≠ total length of sketch-path [mm]: [that is, Range ≠ 360], the Motion-Points become spaced equally over the new Range or Linear Range parameter.


A Path Length is 127.123mm long.

Point Count is 3.

A Range of 360 [default], makes the 3 Points equally spaces with a distance between each Motion-Point = 127.123/3 mm

A Range of 66[deg], makes the 3 Points equally spaced over a total distance of [127.123 * 66 ∕ 360] mm, and the distance between each Motion-Point is [127.123/3 * 66/360].

Phase Offset / Linear Offset: [deg] or [mm]

The position of the 'first' Motion-Point when a wire is not connected to the input-connector of the Motion-Path FB.

When the Offset = 360[degs] or 0[mm], the 'first' Motion-Point is at the start-Point of the sketch-path.

If you generate more than one Motion-Point, the Motion-Points are offset along the sketch-path together.


A Path is 127.123[mm] long.

A Phase of 37[deg] moves the first Point 127.123 * 37 ∕ 360[mm] along the Path.

The motion at the input to the Path FB moves the first Point relative to this position.


Point List and Data Display 

Motion-Point Information box

Headers: Name | Index | Phase

Name is the name given to identify the Point

If you click on Point in the list it shows as Red in the graphic-area.

Index is the Point number identity
Phase is the relative displacement along the sketch-element, relative to the origin of the fist Point of the sketch-element

Display Data of the First Point as:

Radio Buttons to show the phase or linear distance of the first motion-point,

Show Nothing - nothing shows above the FB
Show Distance - the absolute distance along the Motion-Path of the first Motion-Point
Show Phase - the relative angle along the Motion of the first Motion-Point. 360 = 1 Path Length
tog_minusLength Control tab


Path Length using dimension 

You can define the total length of the sketch-path with a 'Controlling Dimension'.

Before you edit the length of the sketch-path, it is best to make sure the geometry of the sketch-path is fully defined with constraints and dimensions.

Controlling Dimension [Dimension Name]

A 'Controlling Dimension' is a dimension that controls the length of the sketch-path. It might give the position of a Belt Tensioner device, or simply define the distance between two arcs / pulleys.

To select a 'Controlling Dimension':

1.Click this box

The Part-Editor opens automatically. In the Part-Editor:

2.Click the 'arrowhead' of a dimension that can control the length of the sketch-loop / 'belt'.

The dimension cannot be 'grey'. Ideally a Line. If you click an arc dimension, you will not be able to add a pulley to that arc later.

The name of the dimension you click shows in the 'Controlling Dimension' as a 'label'.

The Part-Editor closes.

Actual Path Length [mm]

Read only box

When you click a 'Controlling Dimension', this read-only box shows the active length of the Motion-Path / Belt Length.
'Actual Path Length' should equal 'Target Path Length'.

Target Path Length [mm]

Read / Write box

3.Edit to give the length of the Belt you would like.

Note: It is best to make the 'Target Path Length' near to the 'Active Path Length', then, edit the 'Target Belt Length' in small steps with the 'Spin-Box' Tool until it equals the Belt Length you want in your design.

Minimum and Maximum Dimension Value

Set these to limit the range over which the Controlling Dimension can change.


Belt Tooth Pitch 

If you use the Motion-Path as a Belt, with Pulleys, then change the Tooth-Pitch to equal the tooth-pitch for the belt you want to use.

Note: this also changes the Read-only parameter in the Pulley dialog-box.

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