Coil Springs

Use the Add/Edit Coil Springs tool to apply a translational spring-damper force along the line of sight between two parts.

Location: Motion ribbon, Forces group, Springs icon



Click the satellite icon that appears when you hover over the Springs icon to view a list of all coil springs or torsion springs in your model.

Add/Edit Coil Springs

Position the endpoints of the coil spring, then define the preload force, stiffness, and damping rates.

  1. Select the Coil Springs tool on the Springs icon.


  2. Select a location on a part, pin, or fastener to connect the first endpoint of the spring. Hold down the Ctrl key to deselect a feature.
  3. Select a location on another part, pin, or fastener to connect the second endpoint of the spring. (You can select the same location twice, in which case the second click is interpreted as reacting against ground.)
  4. For a linear spring damper, enter the spring stiffness (K) and damping (C) rates.


  5. For a nonlinear spring damper, deselect the check boxes for K and C, then click the icon to open the Profile Editor.
  6. Optional: Enter a preload force (Fi). The default is zero.
  7. Optional: Click-and-drag the arrow manipulator to change the diameter of the spring, or enter a value in the secondary microdialog. Click the chevron to change the number of coils in the spring or the wire diameter. Click the icon to restore the default dimensions.


  8. Right-click and mouse through the check mark to exit, or double-right-click.
Tip:
  • The default spring has no preload. As you drag the endpoints, the installed length (Li) changes dynamically, which also changes the preload value.
  • If you want a damper rather than a spring, change the spring Type in the microdialog and select Damper.
  • Color attributes for the spring can be set using the Property Editor.
  • Use the Section Cut tool to place a spring inside two parts.
  • Suppress/Unsuppress a coil spring to understand its effect on your model. On the spring, right-click and select Suppress. From the Model Browser or Table, right-click and select Unsuppress.

Nonlinear Spring Dampers

Nonlinear stiffness and damping characteristics can be entered for spring dampers for motion analysis.

Using the Profile Editor you can import test data and then edit graphically or through cells in the table. Three interpolation types are available (Akima, Cubic, Linear) and if desired, you can visualize the derivative and extrapolation tails.
  1. For a nonlinear spring damper, deselect the check boxes for the spring stiffness (K) and damping (C) rates as desired.


  2. Click the table icon to open the Profile Editor. (The stiffness curve example below is for a coil spring. Similar profiles are available for dampers and torsion springs.)


    Figure 1. Example of a Coil Spring Stiffness Curve
  3. If you have test data in the expected .csv format, you can drag and drop to import it. (Save a sample file to view the expected format.)
  4. Inspect your data and make changes as needed. Use the options in the Visualization section to help understand how the data is being interpolated/extrapolated.
  5. Edit the data in the table, or use the buttons to remove or reflect the curve as desired.
Tip:
  • Sometimes it is easier to remove the left side data, work on the right side data, and then use the Reflect to Left Side button to reflect your data.
  • Clicking the Replace with Linear Equivalent button will use the Stiffness value (shown greyed out on the microdialog) and display it as an editable curve in the graphical area of the Profile Editor.
  • The Derivative button in the legend is helpful for the Akima and Cubic interpolation methods because it helps you visualize discontinuities in your data. Introducing more points may help you smooth the profile.
  • The Provide Signals to Plant option is available for spring dampers in motion, but is disabled by default. It can be found in the Property Editor and when enabled, the motion Export operation will include the necessary plant signals in the .mdl file for use in MotionView, MotionSolve, and Altair Twin Activate.
  • See the Profile Editor for an explanation of the buttons and visualization options.

Move the Endpoints of a Coil Spring

When editing a coil spring you can reposition the endpoints or move them away from the part.

  1. Double-click the spring to edit it.
  2. Decide whether to use Free Length mode or Preload mode. Be aware that what mode you choose determines what parameters are auto-calculated when you move the endpoints of the spring.
    • Free Length Mode (default): Click the Lf button to have Inspire automatically calculate the preload when you change the free length value or reposition the endpoints.
    • Preload Mode: Click the Fi button to have Inspire automatically calculate the free length when you change the preload value or reposition the endpoints.
  3. Use the graphical handles at the endpoints of the spring to reposition or reattach it. An endpoint on a pin or fastener is always centered.
    • Endpoints snap to features. If you drag far enough, the endpoint will snap to a neighboring part.
    • To place the endpoint at a distance from the current part, double-click the endpoint to open the Move tool. Right-click the exit the Move tool (but continue editing the spring).
  4. Click the spring to open the microdialog.
  5. Update the preload or free length as needed.
    • If in Preload Mode: Enter a preload force (Fi). Click the +/- icon to reverse the direction of the preload. Click the button to reset the preload to zero.
    • If in Free Length Mode: Enter the free length (Lf) of the spring, i.e. the spring's resting state.
  6. Right-click and mouse through the check mark to exit, or double-right-click.
Tip: To move an endpoint but keep it connected to ground, double-click the ground endpoint and use the Move tool. To move a ground endpoint so that it is connected to another part instead, drag the endpoint until it snaps to a feature on the desired part.

Spring Options

Double-click the spring to edit the spring's endpoints, diameter, and preload force.



Figure 2. Coil Spring Manipulator
Endpoints
Click-and-drag the endpoint manipulators to reposition the spring. You can move endpoints along a part, and it will snap to snap points, edges, and faces. You can also use the manipulator to drag an endpoint to a different part.
Spring Diameter
Click-and-drag the white arrow manipulator to change the diameter of the spring, or enter a value in the microdialog. Click the chevron to see additional options.


  • Diameter: Change the diameter of the coils. Click the icon to restore the default dimensions of the coil spring.
  • Coils: Change the number of coils in the spring.
  • Wire Diameter: Change the diameter of the wire.
Preload Force
Click the red arrow to change the direction of the preload force. This indicates whether the spring would expand or contract to reach its free length.

Microdialog Options

Double-click the spring and use the options in the primary microdialog to edit it. Click the to view advanced options.



Figure 3. Coil Springs Microdialog
Type
The default type is spring damper. You can also select just the spring, or just the damper. It is advisable to include some damping.
Set Stiffness
Enter a positive value for the stiffness rate of the spring. (To have no stiffness, set the spring Type to Damper.)
Set Damping
Enter a positive value for the damping rate of the spring.
Preload Mode
Click the Fi button to have Inspire automatically calculate the free length when you change the preload value or reposition the endpoints.
Reverse Preload
Reverse the direction of the preload force in the spring. A positive force pushes; a negative force pulls.
Set Preload
Enter a magnitude for the preload force in the spring. Click the icon to reset the preload to zero.
Free Length Mode
Click the Lf button to have Inspire automatically calculate the preload when you change the free length value or reposition the endpoints.
Set Free Length (Lf)
The free length is the length of the spring in its resting state. If you enter a preload force, the free length is automatically calculated from the stiffness.
Installed Length (Li)
The installed length is the distance between the endpoint manipulators, or the length of the spring as installed. Cannot be edited directly, but you can change the value by repositioning the endpoint manipulators.
Move Spring Endpoints
Opens the Move tool to reposition the spring's endpoints.
Flip to the Other Side
Use to flip/invert the spring damper.

Coil Spring Properties

Refine the behavior and appearance of coil springs using the properties available in the Property Editor (F3).

Damper Scale
Use to increase the damper diameter relative to the spring diameter. The value must be greater than 0, or less than or equal to 1. The default 0.5.
Spring Limits
Spring limits are applied by default, and prevent the spring from expanding or collapsing beyond its natural limits.

Springs Table

The Springs table lists all of the coil and torsion springs in your model and allows you to edit various attributes. Click the Coil tab to view coil springs.

Location: Springs tool, satellite icon



Figure 4. Springs Table
To Do this
Rename a spring Select the cell in the table and then click again to make the field editable.
Change a value Select the cell in the table and then click again to make the field editable. Some fields are for display only.
Sort a column Click the column header. Click repeatedly to toggle between ascending and descending order.
Add or remove columns Right-click on a column header.

Shortcuts

To Do this
Deselect a feature Hold down the Ctrl key and left-click a selected (red) feature.
Exit the tool Right-click and mouse through the check mark to exit, or double-right-click.