Our customer is an industrial automation company that builds robotic arms for assembly lines. It wanted to improve the efficiency and precision of its arms, and the torsion springs in the articulation joints were holding them back. The existing springs were not meeting the performance requirements, which reduced accuracy and increased wear.
Requirements
- Torque: a precise, repeatable torque within a narrow tolerance, so that every joint behaves the same way.
- Durability: more than 500,000 cycles without significant loss of performance.
- Space: a spring compact enough for the tight space inside the joint, with the range of motion the joint needs.
- Environment: continuous use in a changing industrial environment.
Our Solution
Material
We chose AISI 302 stainless steel. It offers high tensile strength together with good corrosion resistance, which gives durable and consistent performance on a factory floor.
Design
The springs have straight torsion arms shaped for the robotic joint. The body is wound compactly to save space while storing the energy the joint needs. As a torsion spring winds up, its inside diameter gets smaller, so the clearance to the shaft has to be right at full deflection. A spring that binds on its shaft gives uneven torque and wears quickly.
Surface Treatment
- Passivation improves corrosion resistance and extends the life of the spring.
- A dry lubricant coating reduces friction between the moving parts. Unlike oil or grease, a dry film does not collect dust, which matters in a joint that has to move smoothly for years.
Manufacturing and Testing
The springs were produced with CNC coiling technology to match the specification of the robotic arms exactly. Torque testing confirmed that each spring delivers the required torque, and fatigue testing simulated operating conditions to check endurance and consistency.
Results
- The precision and life of the robotic arms improved noticeably.
- Assembly tasks became more accurate, and the line ran more efficiently.
- The customer reported less downtime and less maintenance.
What This Project Shows
In automation, small variations add up over hundreds of thousands of cycles. A torsion spring for a robot joint has to deliver the same torque on the last cycle as on the first, and that comes from clearance, friction and tolerance being designed in from the beginning.
If you are designing a joint or actuator that needs a torsion spring, send us your drawing through the contact page, or learn more about our custom torsion springs.
