Dynalloy, Tustin, Calif., offers state-of-the-art shape-memory Flexinol alloy actuator technology. Flexinol actuator springs are designed for applications with low force and high travel requirements. These springs can contract and relax multiples of their length. When Flexinol actuator springs are used within the correct range, repeatable motion from the springs for millions of cycles is reasonable.
Stretch Ratio “SR” is defined as any length “L” over the solid length “SL,” (SR = L/SL) in any state, hot or cold. For example a spring with a SR of 4 cold and 2 hot, assuming a solid length “SL” of 10 mm, would then be 20 mm hot, and 40 mm cold.
While these values will vary depending on how the springs are used, they are still a reasonable starting point for a design. In your calculations, please reference the displacement per coil in conjunction with the stretch ratio to help identify the appropriate length spring to purchase. The online chart gives rough guidelines as to how much current and force to expect with various Flexinol actuator spring.
