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


The Circle

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