Getting Started Tutorials - MechDesigner > Tutorial 3: Add a Sketch-Loop to a Part > Step 3.2: Add Lines & Arcs as Sketch-Loop

Objective of this Step:

•Define a sketch-path and sketch-loop and where it may be used.

•Understand the difference between Merged-Points and Coincident Points

•Add Line and Arc sketch-elements to give a sketch-loop.

Definitions of Sketch-Path and Sketch-Loop

A sketch-Path is a minimum of two sketch-elements, in which the start-Point of second sketch-element is MERGED with end-Point of first sketch-element. You can continue to merge the start-Points of more sketch-elements to extend the sketch-path.

A Sketch-Loop is a Sketch-Path that is also made into a continuous, closed loop, with all end-Points merged

Why add a Sketch-Loop?

Sketch-loop/sketch-path are important constructions in MechDesigner.

We need sketch-paths / sketch-loops for Belt Paths, Chain Paths, Gear Trains, and Extrusion for MD-Solids.

Video of Tutorial 3.2 - Add Sketch-loop with Lines and Arcs

Add 3 Lines and 3 Arcs as sketch-Loop

Add Coincident and Merge-Points compared.

Constraints toolbar: Add Coincident-Constraint

Note: Coincident-Constraints will not give a sketch-loop.

Add two Lines

1.Part-Editor: Click Geometry toolbar > Add Line, Drag in graphic-area.

2.Do Add Line again

Add Coincident Constraint between Points

Start-Points or end-Points of Lines in graphic-area

Do Add Coincident Constraint:

1.Part-Editor: Click Constraints toolbar > Add Coincident Coincident

a.Part-Editor: Click the Point*

b.Part-Editor: Click Point*

The two Points become coincident.

Note: Point must remain Red when you click Point

*start-Point or end-Point at the end of a Line

Click the sketch-element to identify constraints

SHIFT+Click the Point to identify constraints in the Selection-Window

Delete Coincident Constraint

We must show the Coincident-Constraint in the Selection-Window

1.Part-Editor: Right-Click to deselect active commands

2.Part-Editor: CLICK the Point with the Coincident Constraint

There two Points are in the Selection-Window,

But, the Coincident Constraint is NOT in the Selection-Window!

Contextual menu after Right-Click in the Selection-Window

We must:

1.Part-Editor: SHIFT+ CLICK the Point with the Coincident Constraint

The two Points and the Coincident Constraint are in the Selection-Window

In the Selection-Window:

2.Right-click the Coincident-Constraint

3.Click Delete in the contextual-menu

Now, Click and Drag one of the Lines to move them apart again.

Summary:

•Add Coincident does not delete a Point.

•You can delete the Coincident-Constraint.

Geometry toolbar : Merge-Points

Note: This is the inefficient technique, that I rarely use. The Hover technique is much faster - see below.

If I make a mistake with the Hover technique, I use Merge-Points in the toolbar to repair a sketch-loop.

Add two Lines

1.Part-Editor: Click Geometry toolbar > Add Line, Drag in graphic-area.

2.Do Add Line again

Start-Points or end-Points of Lines in graphic-area

Do Merge-Points:

1.Part-Editor: Click Geometry toolbar > Merge-Points

a.Part-Editor: Click Point*

b.Part-Editor: Click Point*

c.Click the graphic-area in a place with no other elements.

* start-Point or end-Point at the end of a Line

Delete Merge-Points !?!

1.Part-Editor: Right-Click to deselect active commands

2.Part-Editor: SHIFT+CLICK the Points that are Merged

Only ONE Point is in the Selection-Window.

Summary:

Merge-Points removes a Point element.

You cannot delete the Merge-Points. Merge-Points is not an element.

Merge-Point to add Sketch-Loop with Hover Technique

Summary of Hover Technique

This is the efficient technique. I nearly always use this technique.

To add the first sketch-element:

1.Add the first sketch-element with the usual drag technique.

To add the second sketch-element:

Before you Mouse-Button-Down...

2.Move you mouse-pointer above the end-Point of the first sketch-element so that only the Point becomes red

3.Mouse-button-down... ...move your mouse... ...mouse-button-up.

The new sketch-element should now be in the graphic-area.

The start-Point of the second sketch-element is Merged with the end-Point of the first sketch-element.

To add more sketch-elements.

Continue to do 2 and 3 to add more sketch-elements.

To add the last sketch-element:

Before you Mouse-Button-Down...

1.Move you mouse-pointer above the end-Point of the last sketch-element ...

2.Mouse-button-down... move your mouse...

Before you Mouse-Button-Up...

3.Hover above the start-Point of the first sketch-element ....

4.... mouse-button-up

A sketch-loop is complete.

Should you fail to hover correctly, repair the sketch-loop with Geometry-toolbar > Merge-Point.

Add Sketch-Loop of Lines and Arcs with Hover Technique

To add a sketch-loop, the start-Point of a sketch-elements is Merged with the end-Point of an adjacent sketch-element.
	Add Line STEP 1: Click Geometry toolbar > Add Line to the left of the graphic-area. STEP 2: Drag the Line, approximately as in the image to the left
	Add Arc STEP 3: Click Geometry toolbar > Add Arc To add the Arc you must Drag two times:. For a sketch-loop: we merge the start-Point of the Arc and the end-Point of the Line. Drag 1: Hover and Drag Hover above the end-Point of the Line so it becomes red, + Drag: ... mouse-button down ... move your mouse-pointer ... mouse-button-up. Drag 2: Locate the radius of the Arc Move your mouse-pointer between the start-Point and end-Point of the Arc. Mouse-button down, again and drag to approximate the radius of the Arc
	Do Add Line and Add Arc commands again, two more times. STEP 4: Add two more Lines and two more Arcs. with the Merge Technique When you add the last sketch-element STEP 5: Hover above the end-Point of the next-to-last sketch-element and the start-Point of the first sketch-element, to complete the sketch-loop.
If you miss a Point as you add the sketch-elements, CTRL+Z or use Geometry toolbar > Merge-Points to merge two Points into one Point. The sketch-loop is similar to the image above.