See also Add Blend-Curve

A Blend-Curve has, and you can edit, these geometric-properties AT the start-Point and its end-Point

Curvature Rate

The default geometric-properties of the Blend-Point equal those of the sketch-element with which you merge at its start-Point and/or end-Point.

You can edit the geometric-properties:

Exactly : with the Blend-Curve dialog-box
Approximately : with the Blend-Curve drag-handles.

Blend-Curve dialog-box

btn_delkeywordEdit Exactly


In the Part-Editor or the Mechanism-Editor:

1.Double-click the Blend-Curve in the graphic-area

- or -

The two separators in the Blend-Curve dialog-box are the:

 Start-Point parameters  

 End-Point parameters 

The parameters in each separator are identical



Start Point  / End Point Parameters

Angle (Units: º):

Maximum = 360º ; Minimum = –360º

Blend check-box:

(DEFAULT) The angle of the Blend-Curve becomes equal to the angle of the adjacent sketch-element at its start-Point (or end-Point)
You can edit the angle of the Blend-Curve at its start-Point (or end-Point).

Curvature k (Units:1 ∕ meters):

Blend check-box:

(DEFAULT) The curvature of the Blend-Curve becomes equal to the curvature of the adjacent sketch-element, at its start-Point (or end-Point)
Enter the curvature for the Blend-Curve its start-Point (or end-Point).

Curvature-Rate dk ∕ ds (Units: 1 ∕ m^2):


Blend check-box:

Make the curvature-rate of the Blend-Curve equal the curvature-rate of the sketch-element with which you merge the Blend-Curve at the start-Point (or end-Point)
Enter a curvature-rate for the Blend-Curve that is different to the curvature-rate of the adjacent sketch-element at its start-Point (or end-Point).

Velocity Scaling

Increase Velocity-Scaling to 'inflate' the Blend-Curve.

Decrease Velocity-Scaling to 'deflate' the Blend-Curve.

Velocity Scaling parameter does not have units.

Default Value = 1 ; Maximum Value = 10 ; Minimum 0.01

Blend-Curve drag-handles

btn_delkeywordEdit Approximately


To show the Drag-Handles

1.Click the Blend-Curve one time

Drag-Handles show at the start-Point and the end-Point.

ArrowheadRed-14-1b Drag-Handle can control:

Velocity-Scaling Factor

Small-CircleRed-14-2 Drag-Handle can control:


You cannot move Drag-Handles when they are Green

Double-click a Drag-Handle to make it Blue

To use the Arrowhead Drag-Handle

1.Double-click a Arrowhead Drag-Handle

The Drag-Handle should be come blue



2.Drag the blue arrowhead

Red-14-1b Rotate the arrowhead around the Point to control the angle of the Blend-Curve at the Point.

Red-14-2 Move the arrowhead further away from the Point to increase the Velocity-Scaling factor


To use the Small-Circle Drag-Handle

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

Move the small-circleRed-14-1b clockwise from 90º (vertically up) towards 270º (vertically down), the Curvature increases from 0 (a straight-line) to +ve Large Value

Move the small-circleRed-14-1b counter-clockwise- from 90º towards 270º, the Curvature increases from 0 to –ve Large Value

Smoothness of sketch-elements

btn_delkeywordNotes on Curvature and Curvature-Rate


Points along a curve have a radius. We call it the curve's Radius-of-Curvature.

In general, the Radius-of-Curvature continually changes as it moves along the curve.

Curvature = 1/Radius-of-Curvature

Thus, Radius-of-Curvature decreases, the Curvature increases.

Curvature of a Line = 0

Curvature of a Circle = 1 ∕ Circle Radius.

E.g. : A circle has a radius of 20mm, its curvature = 1/0.02m = 50/m.

Curvature-Rate i

This is the rate-of-change of curvature (how rapidly curvature changes) with respect to the distance along the Blend-Curve.

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