Step 16.3: Blend-Curve and Motion-Path FB - Basic

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Step 16.3: Blend-Curve and Motion-Path FB - Basic

Blend-Curve sketch-element and Motion-Path FB

Note:

Motion-Points move along sketch-paths that are:

•one or more sketch-elements

•one or more Blend-Curves that you merge to each other, or

•a mixture of one ore more Blend-Curves that you merge with one or more different sketch-elements

Add a Blend-Curve

In this tutorial, we merge a Blend-Curve with a Line and an Arc. The sketch will be an open sketch-path

GST-16-301

STEP 1: Add the Line and Arc sketch-elements

1.Edit the Base-Part

2.Geometry toolbar > Add Line (drag upwards), Add Arc (drag Right-to Left, then downwards)

3.Constraints toolbar > Add Horizontal

(1) Line; (2) end-Point of Line and start-Point Arc; (3) start-Point / center-Point of Arc; (4) center-Point and end-Point of Arc

4.Constraints toolbar > Add Dimension | Radius of the Arc = 20mm; end-Point of the Line to the start-Point of the Arc = 50mm; Length of the Line = 50mm
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STEP 2: Add the Blend-Curve

Add Gearing FB

1.Click Geometry toolbar > Add Blend-Curve Red-14-1

 

Hover above the end-Point of the LineRed-14-1, mouse-button-down ...

.... +Drag ....

... to the start-Point of the ArcRed-14-2 and mouse-button-up.

We merge for you the start-Point and end-Point of the Blend-Curve with the Line and the Arc.

Notes: Default Blend-Curve dialog Parameters

The Blend-Curve is a smooth curve whose parameters are its Angle, Radius of Curvature, and Curvature-Rate.

The Parameters control the Blend-Curve at the start-Point and end-Point and influence its overall shape.

Default Blend-Curve Parameters

We use the Blend check-box to force each of the parameters to equal that of the sketch-element with which you merge its start-Point and/or end-Point.

Start-Point Red-14-1b

•Angle = 90º Angle of the end-Point of the LineRed-14-3 is vertically upwards. Therefore, Angle =+90º

•Curvature = 0. Radius of Line = ∞. Curvature = 1/ Radius = 1/∞ = 0

•Curvature Rate = 0. Curvature of Line = constant. Therefore the Curvature-Rate = 0.
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GST-16-304

End-Point Red-14-2

•Angle = –90º (or 270º) : Angle of the start-Point of the Arc is vertically downwards. Therefore Angle =  –90º (or 270º).

•Curvature  = 50 : Radius of a Arc = 20mm. Curvature = 1/ Radius = 1/0.02m = 50. Therefore, Curvature = 50.

•Curvature Rate = 0. Curvature of the Arc = constant. Therefore, Curvature-Rate = 0.

Edit the Blend-Curve

Blend-Curve dialog - default

Blend-Curve dialog - default

STEP 1: Open the Blend-Curve dialog

Note: You can open the Blend-Curve dialog in the Part-Editor and in the Mechanism-Editor.

1.Double-click the Blend-Curve

or

See How to open a dialog

The Blend-Point dialog is now open.

Start-Point  

The shape of the Blend-Curve is continuous with the sketch-elements to which it is merged.

•Angle = 90 : Equal to the angle of the Line

•Curvature = 0 : Equal to the Curvature of the Line

•Curvature Rate = 0 : Equal to the Curvature Rate of the Line.

Velocity-Scaling - this parameter is a way of inflating the Blend-Curve (similar to blowing up a balloon)

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STEP 2: Edit Blend-Curve dialog > Start/End Point > Curvature-Rate

 Start-Point 

1.Curvature Rate - disable Blend

2.Curvature Rate  = 2400

 End-Point 

3.Curvature Rate, disable Blend

4.Curvature Rate -3000

Click OK-tiny-13-17 to close the Blend-Point dialog

The units of Curvature Rate are 1/m2.

Top-Tip

Rather than calculate values for Curvature Rate, it is easier to look at the shape of the Blend-Curve as you use the Spin-Box.

What is the best Blend-Curve?

It is not possible to know unless you know the application of the Blend-Curve.

 
GST-16-305

This is the new shape for the Blend-Curve.

Curvature-Rate at the start-Point is 2400/m^2

Curvature-Rate at the end-Point is -3000/m^2

Add a Motion Path FB

 

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STEP 1: Add a Motion-Path FB

GST-Icon-FB-MotionPath

1.Click Kinematic FB toolbar > Add Motion-Path FB Red-14-1

 

2.Click the vertical Line

3.Click OK-tiny-11-15 in the Command-Manager
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The graphics-area after STEP 1

Red-14-1b Motion-Path FB

Red-14-2 Motion-Point at the start-Point of the Line sketch-element

Note: Where is the Motion-Point?

When the sketch-path is an open sketch-path, the Motion-Point finds the sketch-element with a start-Point that is nearest to the sketch-element that you click.
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STEP 2: Add Function-Blocks

1.Kinematic-FB toolbar > Add Linear-Motion FB

2.Kinematic-FB toolbar > Add Motion FB

3.Connect the Function-Blocks with wires, in the usual way.

 
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STEP 3: Edit the Output Data-Type of the Motion-FB

1.Edit the Motion FB dialog

2.Motion FB dialog: Motion Parameters Output-Data-Type : RotaryRed-14-1

Output Data-Types in the Motion FB.

Motion (default) - connect the Motion FB to a Motion-Dimension FB.

The motion-values at the output move a Motion-Part to an Angle(degrees) or a Position(mm) relative to a sketch-element in a different Part.

Linear - connect the Motion FB to a Motion-Path FB.

The motion-value at the output from the Motion FB moves a Motion-Point along the sketch-path to a position equal to motion-value.

E.g. 90 at the output from the Motion FB and at the input to a Motion-Path FB moves the Motion-Point by 90mm along the sketch-path from its start-Point*.

Rotary- connect the Motion FB to a Motion-Path FB.

The motion-value at the output from the Motion FB moves a Motion-Point along the sketch-path to a position equal to (motion-value/360 * Total-Length)mm

E.g. 90 at the output from the Motion FB and at the input to a Motion-Path FB moves the Motion-Point ((90/360) × Total-Length)mm along the sketch-path from its start-Point*.

* the start-Point of a sketch-path is the start-Point of the sketch-element you select. Experiment!
Video: Motion-Point moves by Total-Length * 90/360 

Video: Motion-Point moves by Total-Length * 90/360 

STEP 4: Observe the Motion-Point when you cycle the model

1.Press ALT+C keys on your keyboard to cycle the model.  

The default motion has a Rise of 90mm.

The Output Data-Type from the Motion FB is Rotary. Therefore, the Motion-Point moves by 90/360 (or 25%) of the total length of the sketch-path from the start-Point.

2.ALT+C again to stop the model (or Run toolbar > Cycle)

<<< Click to play the video

Motion rise from 0 to 360

Motion rise from 0 to 360

STEP 5: Edit the Motion in MotionDesigner, to have a range of 0 to 360

Position of the Motion-Point = (Input/360) × Total-Length

An input-range of 0-360 moves the Motion-Point from the start-Point to the end-Point of the sketch-path.

 
Video: Motion-Point moves by Total-Length * 90/360 

Video: Motion-Point moves by Total-Length * 360/360 

STEP 6: Edit the Motion in MotionDesigner, to have a range of 0 to 359.99

Why 355.99?

When the motion-value is 360, the Motion-Point may wrap to the start-Point of the sketch-Path.

When the motion-value is 359.99, the Motion-Point will not wrap to the start-Point of the sketch-Path.

359.99 is near to the end-Point of the sketch-path.

<<< Click to play the video