Add Blend-Curve

Toolbar-SE-AddBlendCurve

Toolbar:

left of the graphics-area

Menu:

Add menu > Geometry sub-menu> > Add Blend-Curve

What to do:

1.Edit a Part
2.Click 'Add Blend-Curve' in the Geometry toolbar.
3.Drag in the graphic-area from the start-Point to the end-Point.

'Drag': mouse-button-down [start-Point], move your mouse-pointer, mouse-button-up [end-Point].


The Blend-Curve is now in the graphic-area.


Free-Points and Merged-Points

Add the start-Point and end-Point of the Blend-Curve as:

Free-Points

Add constraints and dimensions to the start-Point and end-Point later.

You can delete constraints and dimensions, if necessary.

Do this for a layout sketch.

See Also: How to Delete a Constraint

Merged-Points

Do this to construct a sketch-path

See: Hover+Drag , merge-points.

If you merge the start-Point or end-Point with a Line, Arc, or a different Blend-Curve [not with a Spline, however], then the:

Angle
Slope
and Curvature

...of the Blend-Curve become the same as the Line, Arc or Blend-Curve sketch-element with which it is merged.

What to do next:

To edit a Blend-Curve:

Approximately: Use Blend-Curve 'drag-handles'.

See Edit Blend-Curve Approximately drag-handles

- or -

Exactly: Use Blend-Curve dialog-box

Example

How:

Selection-Window

Assembly-Tree

Add-BlendCurve

Drag from the start1s-red to the end Point2s of Blend-Curve

Blend-Curven

Pointn at each end of the CAD-Line

The Blend-Curve is a child to the Part.

Add-BlendCurve2

The default Angle, Curvature and Curvature Rate at the start-Point and end-Point of the Blend-Curve are zero.

The images to the left and above are default Blend-Curves.

The Blend-Curve at the top has been added with a drag from bottom-left to top-right.
The Blend-Curve at the bottom has been added with a drag from top-right to bottom-left.

Add-BlendCurve3

Hover + Drag from the end-Point of a different sketch-element to merge the start-Point of as new Blend-Curve.

When you merge the Blend-Curve with a sketch-element, the Blend-Curve matches the Angle, Curvature and Curvature Rate with the other sketch-element.

tog_minus What is a Blend-Curve?

Two Blend-Curves

Two Blend-Curves

A Blend-Curve is a special 2D path, frequently used to guide the path of a Motion-Point:

Blend-Curve parameters at each Point:

Edit its Angle  relative to the Part-Plane.
Edit its Curvature  [Curvature is 1/Radius].
Edits its Curvature-Rate [in the Blend-Curve dialog-box, not with the Blend-Curve Drag-Handles]
Edit its 'Velocity Scaling'

 

tog_minus Why use a Blend-Curve?

Arcs and Lines

Arcs and Lines

Use Blend-Curve to give a smooth sketch-path. See 'Smoothness'.

MechDesigner can guide a Motion-Point along a Blend-Curve and sketch-path with a Motion-Path FB

In general, it is important that the:

The motion of the Motion-Point along the sketch-path does not have discontinuities in position, velocity, acceleration, and jerk.

and the:

The shape of the sketch-path itself does not have discontinuities in angle, curvature, and rate-of-change of curvature.

A Part that is constrained to move along a 'smooth' Blend-Curve sketch-path will vibrate less than if the part is constrained to move along a sketch-path that is less smooth. Lines and Arcs cannot give the same 'smoothness'.

Generally, when it is possible, and there is an advantage, guide a Motion-Point along a Blend-Curve.

 

tog_minus Edit a single Blend-Curve with its 'drag-handles'

Blend-Curve-Drag-Handle1

To show the Drag-Handles

1.Click the Blend-Curve one time

Four drag-handles show: two different drag-handle types at each control-Point of the Blend-Curve.

At each control-Point, there is a drag-handle with an 'arrowhead' 1s-red and a drag-handle with a 'small Circle'2s.

Drag-Handles with an 'Arrowhead' control the Blend-Curve's:

Angle
'Velocity-Scaling Factor' [see Blend-Curve dialog-box]

Drag-Handles with a 'Small-Circle' control the Blend-Curve's:

Curvature

You cannot drag the drag-handles when they are green. You can only drag a drag-handle when it is blue.

1.Double-click a drag-handle with an arrowhead to make it blue

Now you can drag the blue 'arrowhead'

Drag = move your mouse above the arrowhead, mouse-button-down, then move your mouse.

Blend-Curve-Drag-Handle2

Blend-Curve-ArrowheadDragHandle

2.Drag the blue arrowhead drag-handle

1s-red Rotate the arrowhead around the Point to control the angle of the Blend-Curve at the Point.

2s Move the arrowhead further away from the Point to increase the Velocity-Scaling factor

Blend-Curve-SmallCircleDragHandle

1.Double-click a drag-handle with an small-circle to make it blue
2.Drag the blue small-circle drag-handle

Move the small-circle1s-red clockwise from 90º [vertically up] towards 270º [vertically down], the Curvature increases from 0 (a straight-line) to +ve 'Large Value'

Move the small-circle1s-red counter-clockwise- from 90º towards 270º, the Curvature increases from 0 to –ve 'Large Value'


tog_minus Smoothness definitions

Smoothness of Sketch-elements.

You are often concerned with the smoothness of the sketch, especially at the transition between sketch-elements. This is important when the sketch-path is a Path for a Motion-Point that also moves a kinematic-chain.

Smoothness transition between sketch-elements

Angle

Curvature

Curvature Rate

Line joins a Line

Can 'kink', be the same angle (why two Lines?)

NA

NA

Arc joins a Line

Keep the same Angle

Keep the same Curvature (or Radius)

NA

Arc joins an Arc

Keep the same Angle

Keep the same Curvature (or Radius)

NA

Blend-Curve joins a Line

Keep the same Angle

Keep the same Curvature=0 (infinite Radius)

Keep at 0

Blend-Curve joins an Arc

Keep the same Angle

Keep the same Curvature; Radius

Keep at 0

Blend-Curve joins a Blend-Curve

Keep the same Angle

Keep the same Curvature; Radius

Keep the same Curvature Rate

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