Edit a sketch-loop

A Sketch-Loop is an important concept in MechDesigner.

Generally, do not make a sketch-loop unless you intend to add to the sketch-loop a Profile or a Motion-Path FB.

*About Merge-Points

Each Line or Arc you add to the graphic-area has a Point at each end.

In the Part-Editor, to join the Points, you can:

make the Points coincident with the Add Coincident tool

- or -

merge the Points with the Merge-Points tool

In both cases, the Points appear in the graphic-area as one Point. However:

Coincident Constraint does not remove a Point.
Merge-Points removes one Point

Why Merge-Points?

Use Merge-Points when you want to make an open or closed sketch-path.

You can use a sketch path for a Motion-Path FB

You can use a closed sketch-path [sketch-loop] for a Profile element.

tog_minus        Sketch-Loops with the Hover Technique and Merge-Points Tool

There are two ways to merge two Points into one Point:

Use the Hover Technique

Use the Hover Technique as you add the sketch-elements.

Use Merge-Points.

Use the Merge-Points tool after you add the sketch-elements,

You can use Merge-Points, to 'repair' a sketch-loop when the Points coincident but not merged.

Video of Hover Technique and Merge-Points tool

Using the Merge-Points tool and Hover Techniques

tog_minus        Why Sketch-Loops fail

Condition 1: Point are Coincident and not Merged

Points are not recognized as part of a sketch-loop when they are coincident.

You must merge the Points into one Point where each Line and Arc join.

Condition 2: No Branches

You CANNOT merge three Points into one Point - for example, the ends of three Lines or Arcs - you have a 'Branch-Point'. A Branch-Point is not O.K.

You CAN merge two Points, then make a Point at the end of a Line or Arc to be Coincident with the merged Point. This is NOT a Branch-Point.

Condition 3: No Figures of Eight or sketch-elements that touch

A sketch-element can not cross another sketch-element in the same sketch-loop.

A sketch-element cannot osculate, or touch, another sketch-element in the same sketch-loop.

tog_minus        Example sketch-loops

Video of Hover Technique and Merge-Points tool

Video of Sketch-Loops

SketchLoop-circle

The Circle

The Circle is a sketch-loop. A Circle is frequently used for a Cam-Follower.

SketchLoop-lines

Lines

Lines joined, with Points merged.

SketchLoop-line-arcs

Lines and Arcs

Lines and Arcs, with Points merged.

SketchLoop-arcs-arcs

Arcs and Arcs

Arcs and Arcs, with Points merged.

 

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