Connect two parts with a joint, learn about degrees of freedom, and see how real mechanisms work.
Interactive 3D Model: Hinge Joint — two plates connected by interleaving knuckles and a pin, demonstrating a revolute joint.
An assembly positions parts relative to each other using constraints (also called "mates" or "joints") — your robot comes together digitally.
A free body has 6 DOF: translation along X, Y, Z and rotation around X, Y, Z. Constraints remove DOF to hold parts in place.
Two faces or points share the same location. Removes translation DOF perpendicular to the face.
Two cylindrical faces share an axis. Leaves rotation around and translation along the axis.
Maintains a fixed gap between faces. Like coincident but with a specified separation.
Forces faces or edges to stay parallel or at right angles to each other.
A hinge. One part rotates around a fixed axis. Used for: arm joints, flippers, lids.
A slider. One part moves along a straight line. Used for: linear actuators, drawer slides, elevators.
Combines rotation and sliding along the same axis. Used for: lead screws, telescoping mechanisms.
Parts are locked together. Used for: bolted connections, welded frames, glued assemblies.
A free body in 3D space has how many degrees of freedom?
DOF = the number of independent movements a body can make. A fully constrained body has 0 DOF.
Translations: Tx, Ty, Tz (movement along axes). Rotations: Rx, Ry, Rz (spinning around axes).
Each constraint removes one or more DOF. A revolute joint leaves exactly 1 DOF (rotation around one axis).
You need to model a simple wheel for a drivetrain. Think through the feature sequence.