Edit a sketch-path or sketch-loop

A Sketch-Loop is a sketch that does not have breaks and the Points that join the sketch-elements are merged into one Point.

Generally, do not make a sketch-loop unless you intend to add to it a Profile/Extrusion [Solid] 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, you have two options when you want to the ends of sketch-elements together. You can:

make the Points coincident with Constraints toolbar > Add Coincident

- or -

merge the Points with Geometry toolbar > Merge-Points

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

Add Coincident Constraint does not remove a Point.
Add 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:

Dynamically, as you add the sketch-elements, with the Hover Technique
Later, after you add the sketch-elements with Geometry toolbar > Merge-Points.

Video of Hover Technique and Merge-Points tool

Using the Merge-Points tool and Hover Techniques

tog_minus        Why do Sketch-Loops fail?

Condition 1: Coincident Points, 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: 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 different Point become Coincident. This is NOT a Branch-Point.

Condition 3: Figures=of-Eight

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



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



Lines joined, with Points merged.


Lines and Arcs

Lines and Arcs, with Points merged.


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