Motion-Path FB

see Add Motion-Path FB


A Motion-Path FB adds a Motion-Point to a sketch-path.

The Motion-Point is a kinematic-element, to which we can join a Part with a Pin-Joint.

The motion-values at the input-connector to the Motion-Path FB specify the motion of the Motion-Point along the sketch-path.

The Data-Type at the input to the Motion-Path FB is important. When the Data-Type at the input to the Motion-Path FB are:

Linear Units (mm), then the:

Distance the Motion-Point moves along the sketch-path = Input Motion-Value (units)

Angular Units (degrees), then the:

Distance the Motion-Point moves along the sketch-path = Input Motion-Value (degrees) /360 (units)

See also Motion-Path Range and Motion FB


Note:

A Sketch-Path is one to many sketch-elements joined end-to-end with Merged-Points . Sketch-Paths for a Motion-Path FB are:

Open(Γ), or
Closed(Δ), or
Crossed(α), or
Not crossed(ε).

Open Motion-Path FB dialog-box

Icon-FB-MotionPath

Edit the Motion-Path FB:

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

- or -

The Motion-Path dialog-box is now open.


Motion-Path dialog-box

Motion-Path dialog-box

Motion-Path dialog-box

btn_delkeywordPoint-Parameters tab

Dialog-13.2-MotionPathFB-PointParameters

Point Parameters 

Number of Motion-Points:

Edit Number of Motion-Points > 1 to add more Motion-Points. They are distributed equally along the sketch-path.

If you edit Number of Motion-Points  you MUST also click the Regenerate Motion-Points button.

In the default case, Motion-Points (>1) are at equal increments along the full extent of the sketch-path. E.g.: If a Circle is the sketch-path, then 12 Motion-Points will be at each 'hour' if we imagine the circle to be a clock-face.

Range (deg) | Default = 3600 ;

Linear Range (mm)  | Default = full length of sketch-path.

Range and Linear-Range are two ways to equate the length of the sketch-path. Each option is convenient at different times.

If you edit the value of Range or Linear-Range, then the other automatically updates its value, proportionally.

What is 100% of the sketch-path.

Range: equates the full length of the sketch-path to 360-degrees of a circle.

Linear-Range: equates the full length of the sketch-path to its actual linear length.

See also Motion-Path Range and Motion FB


A different Range might be a Percentage Range, to equate the full linear length of the sketch-path to 100%.

A different Range might also be a Unit Range, to equate the full linear length of the sketch-path to 1.


When to use edit a Range parameter?

Range parameters specify the extent over which to distribute Motion-Points along the sketch-path.

When Range or Linear Range are equal to a default value, the Motion-Points distribute along a full extent of the sketch-path.

When Range or Linear Range are less than the default value, the Motion-Points distribute along a reduced extent of the sketch-path.

Example: Actual length of a sketch-path is 127.5mm

Number of Motion-Points = 3.

Range =360, (and Linear-Range = 127.5), the 3 Motion-Points are equally spaced. The distance between each Motion-Point = 127.5/3mm =42.5mm

Range = 120 (Linear-Range automatically is 42.5). The 3 Motion-Points are spaced over a linear-length of (127.5 × 120 ∕ 360 = 42.5mm.

The Position of Motion-Point #1 = 0mm, Motion-Point #2 = 21.25, and Motion-Point #3 = 42.5mm

Phase Offset (deg) Default = 0

Linear Offset (mm) | Default = 0

Phase Offset and Linear Offset are two ways to equate the position of Motion-Point #1 along the sketch-path.

Both parameters move the position of all Motion-Points along the sketch-path. The two offset values indicate the position of Motion-Point #1 when the motion-value at the input-connector of the Motion-Path FB is equal to 0; or, when a wire is not connected to its input-connector.  If you generate more than one Motion-Point, the Motion-Points are offset along the sketch-path together.

Phase-Offset: equates the length of the sketch-path to 360-degrees of a circle.

Linear-Offset: equates the length of the sketch-path to its actual linear length.

Example:

A sketch-path is 127.5mm long.

A Phase-Offset = 40(deg) moves the Motion-Point #1 to 127.5 * 40 ∕ 360(mm) = 51mm along the sketch-path.

All other Motion-Points move by the same offset distance.

Re-generate Motion-Points button

Click to the Number of Motion-Points parameter.

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

Dialog-13.2-MotionPathFB-PointList

Point List and Data Display 

Motion-Point Information   - Read-Only

Headers: Name | Index | Phase

Name is the name given to identify the Motion-Point

If you click on a Motion-Point in the list it shows as red in the graphic-area.

Index is the Motion-Point number identity
Phase is the relative displacement along the sketch-path, relative to the fist Motion-Point

Display Data of the First Point as:

You can continually display the distance travelled by Motion-Point #1 as you cycle the model.

Show Nothing - nothing shows above the Motion-Point #1 in the graphic-area
Show Distance - the linear distance Motion-Point #1 has moved along the Motion-Path
Show Phase - the angular-distance Motion-Point #1 has moved along the sketch-path, with 360 equal to full extent of the sketch-path.
btn_delkeywordLength Control tab - Path Length using Diagram

Dialog-13.2-MotionPathFB-PointLength

Path Length using dimension 

You can specify the length of the sketch-path with a Controlling Dimension, This is typically used to control the length of a Belt.

Before you edit the length of the sketch-path, ideally fully defined the sketch-path with constraints and dimensions or the results may be unexpected.


Controlling Dimension (Dimension Name)

The Dimension-Name that controls the length of the sketch-path.

1.Click the Controlling Dimension box

The Part-Editor opens.

2.Click the 'arrowhead' of a dimension

The dimension will control the total length of the sketch-path - see Note below.

The Part-Editor closes.

The Dimension you click is now in the Controlling Dimension

Actual Path Length - Read only

The Actual Path Length (mm) is the total length of the sketch-path.

Target Path Length (mm) Read / Write box

3.Enter the length of the sketch-path as a target length.

Minimum and Maximum Dimension Value

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

Notes: Controlling-Dimension and the Sketch-Path

Ideally, fully specify the sketch-path, so that the dimension you select will update the length of the sketch-path in a predictable way.

Ideally select the dimension for a Line. If you click an arc dimension, you will not be able to add a pulley to that arc later.

The dimension cannot be 'grey' before you select it.

Note: Editing the Target Path Length

Small difference between Actual Path Length and Target Path Length give more predictable results.

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.

Dialog-13.2-MotionPathFB-BeltToothPitch

 Belt Tooth Pitch 

The Belt-Tooth-Pitch does not control the belt length.

If you add a Pulley element at an Arc in a sketch-path, then the diameter of the Pulley (and the Radius of the Arc) is a function of the number of teeth (See Pulley dialog-box ) AND the Belt-Tooth Pitch.


About Motion-Range and Output Data Type from a Motion FB

The motion of the Motion-Point along the sketch-path is a function of the Data-Type at the input-connector to the Motion-Path FB: Does the data-type have Linear or Rotary units?

When you connect a wire from the output of a Motion FB you must also set the Output Data Type with the Motion FB dialog-box (see Motion FB dialog-box).

Motion FB > Output Data Type

There are three Output Data Types

Motion - do not use with a Motion-Path FB
Linear - see below
Rotary - see below

Motion FB > Output Data-Type - Linear

The position of the Motion-Point is scaled on a 1 : 1 basis with the motion-value that output-connector of the Motion FB and input-connector its Motion-Path FB

∴ the position of the Motion-Point along the sketch-path = motion-value at input-connector in linear units.

Motion FB > Output Data-Type - Rotary

The sketch-path has a scale of 0 to 360. A motion-value at the input of 360 would move the Motion-Point the complete extent of the sketch-path.

∴ the position of the Motion-Point along the sketch-path = motion-value at input-connector × total length of the sketch-path / 360


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