Physical Dynamics

Physical Dynamics is an option in Collision Detection that allows you to see the motion of assembly components in a realistic way.

With Physical Dynamics enabled, when you drag a component, the component applies a force to components that it touches. The effect is to move or rotate contacted components within their allowable degrees of freedom. The dragged component reacts to a collision by rotating within its allowable degrees of freedom or by sliding against a constrained or partially constrained component to allow the drag to continue.

Physical Dynamics propagates throughout the assembly. The dragged component can push aside a component, which then moves into and pushes aside another component, and so on.

Physical Dynamics works best and is most meaningful on assemblies that have only a few degrees of freedom. Add all appropriate mates prior to running Physical Dynamics.

You cannot use Physical Dynamics and Dynamic Clearance at the same time.

Conveyor Example

To move a component using physical dynamics:

1. Click Move Component or Rotate Component on the Assembly toolbar.

2. In the PropertyManager, under Options, select Physical Dynamics.

3. Move the Sensitivity slider to change the frequency with which Physical Dynamics checks for collisions. Move the slider to the right to increase the sensitivity. At the most sensitive setting, the software checks for collisions every .02mm (in model units). At the least sensitive setting, the check interval is 20mm.

   Use the most sensitive settings only for very small components, or for components with complex geometry in the collision area. When you use the maximum sensitivity when checking for collisions between larger components, the drag is very slow. Use only the sensitivity setting you need to see the motion in your assembly.

4. If needed, specify the components to participate in the collision:

   1. Click These components.

   2. Select components for Components for Collision Check.

   3. Click Resume Drag.

      Choosing specific components in Collision Detection improves the performance of Physical Dynamics. Choose only those components that are directly involved in the motion you are testing.

5. Select Dragged part only to check for collisions with only the components that you selected to move. When cleared, the components that you selected to move, plus any other components that move because of mates with the selected components, are checked.

6. Drag a component in the graphics area.

   When Physical Dynamics detects a collision it adds a contact force between the colliding parts and allows the drag to continue. The force remains as long as the two parts touch. When the two parts no longer touch, the force is removed.

   You can select one component after another within a single command.

7. Click OK .

Initial Collisions

If the component you drag has an initial collision with another component, SolidWorks displays a message in the graphics area and all components involved in the collision turn transparent. Physical Dynamics is turned off for collisions between the transparent components. You can continue the drag, and collide with and apply a force to other components.

To activate a collision between initially colliding components

1. Drag your component until it no longer interferes.

2. Release the drag.

3. Drag again.

   The components are no longer transparent, and Physical Dynamics works.

Dragging by Center of Mass

When you click a component to drag it, a center of mass symbol appears at the component's center of mass. If you click the symbol and drag the component, you are dragging by the center of mass. If you click outside the symbol and drag, you are dragging by the point on the body you clicked.

You apply a moment arm to a component if you drag outside the center of mass, which causes the component to rotate within the allowable degrees of freedom.

NOTE: The center of mass symbol appears during Move, but not during Rotate. The Free Drag option in Rotate Component is by definition rotation about the center of mass.