Compare a Motion-Part to a Motion-Point

A Motion-Part and a Motion-Point are similar elements:

•Motion-Part, is a Part, whose motion is constrained by a joint, whose position is identified by its Motion Dimension, and whose motion is defined by the input to the Motion-Dimension FB.
•Motion-Point, is a Point, whose motion is constrained by a sketch, whose position is identified by its Motion-Point Dimension, and whose motion is defined by the input to the Motion-Path FB.

The Motion-Path FB and Motion-Dimension FB - compared

Motion-Path FB & Motion-Point:

Motion-PathFBMotion-Point-Dimension

'Add Motion-Path FB' does three things:

1.Adds a Motion-Point1s-red to a prepared sketch-element [or sketch-path]
2.Adds a Motion-Path FB2s to the graphic-area
3.Adds a dimension to the Motion-Point FB3s to indicate how far the Motion-Point has moved along the sketch-path.

Note:

To see the Motion-Point Dimension3s you must:

1.Edit the Motion-Path FB, and
2.Click the Displacement radio-button in the  Point List and Data Display  separator of the Motion-Path FB dialog-box.

The displacement of the Motion-Point along the sketch-path shows above the Motion-Path FB.

Motion-Point: is a Point constrained by a sketch-path. Its position from the start-Point of a sketch-path is the total of values given by:

•Motion-values at the input-connector of the Motion-Path FB
•Base-Value, as entered in the Point Parameters separator Motion-Path FB dialog-box.

Motion-Dimension FB & Motion-Part.

MotionDimensionFB

'Add Motion-Dimension FB' does three things:

1.Specifies the position of a sketch-element [Line or Point] in a Motion-Part1s-red relative to another sketch-element [Line or Point] in another Part
2.Adds a Motion-Dimension FB2s to the graphic-area.
3.Adds a Motion Dimension3s between the sketch-elements in the two Parts.

Motion-Part: is a Part constrained by a joint. Its position from a sketch-element in a different Part, is the total of values given by:

•Motion-values at the input-connector of the Motion-Dimension FB.
•Base-Value as entered in the Motion-Dimension FB dialog-box.

Why use a Blend-Curve

Blend-Curve1a

About the Blend-Curve

A Blend-Curve is a sketch-element.  A Blend-Point has a start-Point and an end-Point.

Use the Blend-Curve dialog-box to specify, at its start-Point and its end-Point, these parameters:

oAngle
oCurvature
oRate-of-Change of Curvature

You can also specify a 'normalisation' parameter we call Velocity-Scaling. This controls the overall length and shape of the Blend-Curve.

Question: Why do we need a Blend-Curve?

Answer: To eliminate a curvature-discontinuity.

Question: What is a curvature-discontinuity?

Answer: At the instant a Motion-Point moves between sketch-elements that have different radii, [e.g. from an Arc to a Line [and vice versa], or from an Arc to another Arc] it experiences a curvature-discontinuity.

Question: What is wrong with a curvature-discontinuity?

Answer: If you join a machine element to the moving Motion-Point, the curvature-discontinuity between different sketch-elements will give rise to vibrations of the machine-element. To reduce mechanical vibrations, you must eliminate the curvature-discontinuity.

The purpose of the Blend-Curve element is to eliminate curvature-discontinuities as the Motion-Point moves along the sketch-path and between sketch-elements.

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