By Nate Frazee

When modeling a leaf spring, the length of the spring stays constant, while the radius changes size based on the amount of compression. This design intent can be captured in the sketch.

- In Creo, create a
**Sketch**of an**Arc**. - Create two strong dimensions using the
**Normal**command.

a.) A dimension from the horizontal base reference to the arc tangent. This will represent the height of the arc while compressed.

b.) A dimension for the radius of the arc. This dimension will be made variable in the next step.

- Create a
**Perimeter**dimension for the arc length. While creating this dimension, the radius dimension will be made variable.

a.) Click**Perimeter**and select the arc. The arc will be governed by the perimeter dimension.

b.) Click**OK**.

c.) Select the arc radius dimension to be the dimension that is driven by the perimeter dimension.

d.) A perimeter dimension is created for the arc. Type in an arc length for the perimeter. The radius dimension will vary based on the arc length.

4. It is also possible to change the height dimension (which would change based on amount of compression). This will also change the radius of the arc.

**Extrude**and the desired thickness and length.

For more information about advanced sketching and other topics in Creo, see our line-up of available Creo training classes.