In our latest blog Mike Hales, our Production Manager, will look at the benefits of prestressing when manufacturing springs.
Prestressing can increase the load-carrying capability and the spring’s ability to withstand stress ultimately improving the fatigue life of a spring.
Dimensional changes will take place when a spring is prestressed during its manufacture. The process of prestressing a compression spring is relatively simple. The manufacturing process involves the spring being coiled, stress relieved and ground. After this process has taken place, the spring is placed on a press and compressed to a fixed or solid position which is greater than its maximum working position.
Repeating this process at least three times will result in the spring being shorter than the coiled spring, with the correct initial set-up it will be possible to achieve the required final length.
Tension and torsion springs can also utilise prestressing during the spring manufacturing process. When it comes to the manufacture of tension springs, the amount of initial tension is reduced and is therefore not often carried out.
In order to successfully prestress torsion springs, special jigs are required. The leg relationship will change (the number of coils slightly increases).
As prestressing is an additional operation in the manufacture of a spring, this will increase its unit cost. However, the benefits of prestressing during the manufacturing process will generally outweigh the additional cost.
Next month our Managing Director, Tim Page will look at the use of conical compression springs.
In our latest blog Tim Page analyses the ‘torsion spring’ and the difference in their mode of operation in comparison to extension and compression springs.
Torsion springs are stressed in bending, whereas compression and extension springs are stressed in torsion, in effect they are a wound-up cantilever.
As a torsion spring can supply or withstand torque they require some form of spring leg. The type of spring leg depends on its application and can vary from a simple tangential straight leg or it can become a lot more complex. In order to reduce manufacturing tolerances and difficulties – the simpler the better!
The torsion spring is unable to withstand as great a deflection if it is not operated in a wind-up condition. The spring designer will specify the spring requirements as a load applied to the legs and it’s necessary to convert this into a torque.
When torque is applied to a torsion spring the body length will increase by one wire size for every 360 degree of deflection, this can result in the spring binding if not enough space has been allowed, with the application resulting in spring failure.
As most torsion springs work over a shaft, if the mean diameter of the spring decreases and not enough clearance is allowed between the shaft and the spring, the spring will bind onto the shaft. Consequently the legs will take all of the torque resulting in a permanent set.
When applying tolerances to a spring component it’s essential that this is factored in with the spring design and manufacture.
We hope you found this post on ‘Torsion springs’ informative, please do get in touch if you would like to know more, email us or call 01425 611517.
In our next blog Jon Davies will review ‘flat strip materials’.
Tim Page, Managing Director
Southern Springs & Pressings manufacture a wide range of springs, wire forms, flat strip components and tailor made metal products to meet your needs. We also provide specialist services such as tooling, assembly and design solutions to help deliver your products to market.