﻿ Geometry | Coincident

# Geometry | Coincident

### Add Coincident Toolbar :

Part-Editor : Constraints toolbar

Menu :

Part-Editor : Add menu > Geometry sub-menu> > Constraints sub-menu > Add Coincident

To add :

Click Add Coincident Constraint, then:

 • two Lines (or: a Line and the X-axis or Y–axis)

- or -

 • a Point and a Line (or a Circle), (or a Point and the X-axis or Y–axis)

- or -

 • two Points

- or -

 • or a Point and a Motion-Point

Result :

If the two sketch-elements have a total of more than two degrees-of-freedom:

 • the two Lines (or a Line and the X or Y–axis) become collinear

- or -

 • the Point becomes coincident with the 'ray' of the Line,
 • the Point becomes coincident with the circumference of the Circle

- or -

 • the two Points become coincident.

Note: If the two sketch-elements have a total of 1 degree-of-freedom, then the two sketch-elements cannot become 'coincident'.

To Delete :

 1 SHIFT+CLICK a sketch-element with a Coincident Constraint

The sketch-element and Coincident Constraint show in the Selection-Window.

 2 Right-click the Coincident Constraint element in the Selection-Window
 3 Click Delete in the contextual-menu

In MechDesigner, you cannot remove more than two degrees-of-freedom from a Point.

For example, you cannot do these two steps:

 STEP 1: Add a Coincident Constraint between a Point and a Line (or axis) - this removes 1 degree-of-freedom from the Point.
 STEP 2: Add a Coincident Constraint between the same Point and another Point - this attempts to remove a further 2 degrees-of-freedom - it CANNOT!

Why:

 • A Coincident Constraint between a Point and a Line removes 1 DOF from the Point.
 • A Coincident Constraint between a Point and a Point removes 2 DOF from the Point.

Thus, delete the constraint between the Point and the Line (STEP 1), before you add the constraint between the two Points (STEP 2).

About Point Symbols

 • '+' : centre-Points - at the centre of Arcs and Circles
 • 'O' : start-Point or end-Point - at the end of a Line and Arc
 • : centre-Point that is coincident with a start-Point or end-Point.

You may need to select the '+' or the 'O' with a command, and it is important to see the difference between the two Points and be able to select one Point or the other Point.

When a centre-Point is Merged with a start-Point or end-Point of a Line or Arc, the symbol is a '+'. You cannot select one or the other, because there is only one Point.

 • : Motion-Point - added to a sketch-element with Add Motion-Path FB.
 • : Motion-Point coincident with a start-Point or end-Point.

See also :

All About Sketch-Loops

Notes :

Use Add Coincident between two Points for construction geometry.

Use Merge-Points for sketch-loops and sketch-paths.

Points that are 'coincident' give you the option to delete the Coincident Constraint later.

#### Coincident constraints in the Graphic-Area, Selection-Window and Geometry-Tree.

Before

After

Select:

In Selection-Window &

Geometry-Tree as...  • Two Lines:
 • Line and X or Y–axis

The Lines become collinear

CoincidentLtoLn  • Point and Line (or X & Y–axis)
 a. The Point lies on 'ray' of the Line.

CoincidentPtoLn  b. A Point in a sketch-element and Line  c. The X or Y–axis or Ray of the X or Y–axis.  • Point and Circle:

The Point is constrained to lie on the circumference of a Circle

CoincidentPtoCn  • Point and Point:

The Points become coincident

CoincidentPtoPn

Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd