Assembly Design > Assembly Design > Using Assembly > Placing Components > Predefined Sets > About Motion Axes in Predefined Constraint Sets
About Motion Axes in Predefined Constraint Sets
In predefined constraint sets, motion axes:
Determine which placement constraints are used to place the component in the assembly. The constraints restrict the motion of bodies relative to each other, reducing the assembly's total possible degrees of freedom (DOF)
Define component motion limits
Before selecting a predefined constraint set with a motion axis, you must understand how the placement constraints and degrees of freedom are used to define movement. Each motion axis is associated with a unique set of geometric constraints that define specific Degrees of Freedom. DOF define allowable translational or rotational movement (or both) of a component in the assembly.
Define properties for the motion axis in the Placement subtab of the Component Placement tab:
The default zero position is the initial placement position of a reference on the component relative to a reference on the assembly.
The zero position is the current manually set zero position.
The motion axis regeneration value determines the position of the component in the assembly when the model is regenerated. The regeneration value of a motion axis is a dimension that can be used in family tables, relations, and wherever dimensions are used. This value is ignored during dragging and analysis operations. A motion axis regeneration value can be set in the Component Placement tab when placing the component or while editing a motion axis in Assembly. In Mechanism Design, it can be set from the Motion Axis definition dialog box.
Limits on the motion axis, friction, and restitution of the axis are constraint set parameters. Use the motion settings options of the Placement subtab to set these parameters. Click Dynamic properties to set friction and restitution parameters. To simulate impact forces for a motion axis, specify a value for the coefficient of restitution. The coefficient of restitution is defined as the ratio of the velocity of two entities before and after a collision.
 Although configured motion axes are visible in Assembly mode, it is easier to redefine them in Mechanism Design where conflicts between different motion axes are visible. In Assembly, each motion axis is configured independently and conflicting motion limits are not visible.