Constraint Types in Assembly Design

Mechanical Design	Assembly Design	Constraint Types in Assembly Design Description of the constraints available with Assembly Design
Technical Article

Abstract

This article describes the constraint types available in Assembly Design.

Constraints in Assembly Design
Constraint Types in Assembly Design

Constraints in Assembly Design

Constraints allow you to position mechanical components correctly in relation to the other components of the assembly. You just need to specify the type of constraints you wish to set up on one or between two or between three components, and the system will place the components exactly the way you want.

You can also use constraints to indicate the mechanical relationships between components. In this case, constraints are included in the specifications of your assembly.

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The Fix Constraint

Fixing a component means preventing this component from moving from its parents during the update operation. The component is fixed by selecting one of its geometrical element at least.
There are two ways of fixing a component:

By fixing its position according to the geometrical origin of the assembly, which means setting an absolute position.
This operation is referred to as "Fix in space"
By fixing its position according to other components, which means setting a relative position.
This operation is referred to as "Fix".

By default, the Fix command fixes components in space.

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The Offset Constraint

When defining an offset constraint between two components, you need to specify how faces should be oriented.

The offset value is always displayed next to the offset constraint.

The following table shows the elements you can select:

	Point	Line	Plane	Planar Face
Point	(1)	(1)	(1)	(1)
Line	(1)	(1)	(1)	(1)
Plane	(1)	(1)	(1)	(1)
Planar Face	(1)	(1)	(1)	(1)

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The Coincidence Constraint

Coincidence type constraints are used to align elements.

Depending on the selected elements, you may obtain concentricity, coaxiality or coplanarity..

The following table shows the elements you can select:

	Point	Line	Plane	Planar Face
Point	(2)	(2)	(2)	(2)
Line	(2)	(2)	(2)	(2)
Plane	(2)	(2)	(2)	(2)
Planar Face	(2)	(2)	(2)	(2)

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The Angle Constraint

Angle type constraints fall into three categories:

Angle
Parallelism (angle value equals zero)
Perpendicularity (angle value equals 90º)

When setting an angle constraint, you will have to define an angle value. Note that this angle value must not exceed 90º.

The following table shows the elements you can select:

	Line	Plane	Planar Face
Line	(6, 8, 11)	(6, 8, 11)	(6, 8, 11)
Plane	(6, 8, 11)	(6, 8, 11)	(6, 8, 11)
Planar Face	(6, 8, 11)	(6, 8, 11)	(6, 8, 11)

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The Contact Constraint

Contact type constraints can be created between two planes or faces.

The common area between the two planes can be a plane (plane contact), a line (line contact) or a point (point contact).

The following table shows the elements you can select:

	Planar Face	Sphere	Cylinder	Cone	Circle
Planar Face	(20)	(22)	(21)
Sphere	(22)	(20)		(25)	(25)
Cylinder	(21)		(20, 21)
Cone		(25)		(20, 21)	(25)
Circle		(25)		(25)

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