A mate primitive is a mate that constrains at most two degrees of freedom. By replacing a mate with a mate primitive, you can remove redundant constraints on a component by limiting degrees of freedom on the component one at a time.

When trying to minimize constraints on a model to reduce redundancies, first try to place rigid components into rigid groups, and replace formed hinges with hinge mates. To further reduce constraints on the model, try substituting mate primitives for other mates.
The following table displays the number and type of degrees of freedom constraints applied by a mate primitive on a component.
Mate Primitive Number of Degrees of Freedom Constrained Mate Selections
Point-to-Plane 1 Translational Point coincident with a plane
Point-to-Line 2 Translational Point coincident with a line
Perpendicular 1 Rotational Line perpendicular to a line
Parallel Axis 2 Rotational Line parallel to another line
Line-to-Plane

1 Translational

1 Rotational

Line coincident with a plane
Substituting mate primitives is a manual process and requires detailed understanding of the intended motion. Orient the mate primitives properly to optimize the constraint reduction.

For example, you can mate a slider with a square rod by creating a pair of plane-to-plane coincident mates that each reference one of the two perpendicular faces of the rod. This plane-to-plane mate introduces a redundant constraint because both faces are constraining rotation about the axis of the rod.

If you substitute a line-to-plane type mate primitive for one of the plane-to-plane coincident mates, there is no mate redundancy.