Solidworks Assembly constraints

Constraints are the most important features of an assembly since they limit the degrees of freedom of a part allowing the designer to specify movability of the part.

Several mate constraints exist within Solidworks ranging from simple standard mate constraints like coincident mates that constrains two surfaces to each other, concentric mates that constrains two cylindrical parts to move along the same axis to mechanical mates like cam, slot, hinge and gear mates.

I will do some simple mates to illustrate this capability inside Solidworks. To begin we need to create a new assembly.


Next we can add the components that make up the assembly.

For this first illustration will show how a hinge constraint works.

Solidworks Assembly Constrains

Once you have placed the components onto the assembly you can proceed to create the constraint. Move to the            assembly tab and click on the mate icon.

Solidworks Assembly Constrains

Doing this pulls up a window that lets you define your mate properties. Proceed to the mechanical mates select the hinge mate.

You can then select the parameters for your constraints. For the concentric sections you can do with the two cylindrical as shown below.

For the coincident sections select the parts of the hinge that are in contact.

Doing this automatically sets up the mate. Similar to a hinge the joint allows one part of the assembly to revolve relative to another fixed component.

For this particular mate you can choose to specify the angular limits of the mate by checking the box just below the concentric selections window.
Other mates like the concentric mate is simple and only needs one to identify the concentric components in the assembly. Say in the assembly below I wanted to constrain the two components on the L rod.

Clicking on the mate constraint and selecting the inner surface of the fixtures and the surface of the L rod specifies the mate selections.
You can specify the offset of the two components on the L rod from each other by using the coincident mate and specifying the offset distance.

This has barely scratched the surface on the capability of Solidworks mate constraints and the numerous number of applications that require such great diversity.