Total Degrees of Freedom

Rotation Axis

Translation Axis

Connection Type

Constraints associated with specific DOF

0

0

0

Weld—Glues two bodies together.


0

0

0

Rigid—Glues two parts together while changing the underlying body definition. Parts constrained by a rigid connection constitute a single body.


1

0

1

Slider—Translates along an axis.

Planeplane coincident

1

1

0

Pin—Rotates about an axis.


2

2

0

General

Pointpoint align if the point is on an edge.
Edge on plane.

2

1

1

Cylinder—Translates along and rotates about a specific axis.

Point on line
Planeplane orient

2

0

2

General

Edge on plane provided the plane is neither perpendicular nor parallel to the edge
Planeplane orient

3

3

0

Ball—Rotates in any direction.

Pointpoint align

3

2

1

General

Edge on plane
Point on line (line and edge must align)

3

1

2

Planar—Bodies connected by a planar constraint move in a plane with respect to each other. Rotation is about an axis perpendicular to the plane.

Planeplane coincident/parallel

3

0

3

General

Planeplane orient
Planeplane orient (not parallel to the first set of planes)

4

3

1

Bearing—Combines a ball connection and a slider connection.

Point on edge

4

2

2

General

Edge on plane

4

1

3

General

Planeplane orient

4

3

1

Slot

Point on a nonstraight trajectory

3

3

0

Gimbal—Aligns the centers of two CSYS (see below).

Point to point

5

3

2

General (see below).

Point on plane

6

3

3

6DOF—Rotates and translates in any direction (see below).


In addition to the connection set constraints, you must consider the constraints imposed by the servo motors you apply to your model. Servo motors are enforced displacements, velocities, and accelerations that remove degrees of freedom.
Be careful to apply only as many predefined constraint sets as you need to restrict the mechanism's movement. If you overconstrain the mechanism, you will have redundancies, which can give inaccurate reaction results in dynamic analyses.
For more detailed information on component placement and constraint sets, search the Assembly area of the Help Center.
