Over time, a spring that is exposed to a load loses it strength. The technical term for this is relaxation. Today, Lesjöfors uses a technique at its plant in Herrljunga that enables springs to better maintain their strength over time. This technique is known as hot presetting.
“We began working with hot presetting in 2006, when a customer needed to produce springs that offered higher performance,” explains Lars Blidberg, President of Lesjöfors Industrifjädrar. “Since then, we have developed a unique technique in this area.”
Hot presetting itself is not a new technique. It is used, for example, to produce valve springs for car engines, where it is vital that springs do not lose their strength over time. The process of hot presetting involves heating the springs to between 150 and 200 degrees Celsius. The springs are thenoverloaded, compressed and cooled, which allows them to “set” in a more compressed position.
“To put it simply, hot presetting gives the springs a builtin force that causes them to try to ‘spring back.’ This force improves the performance and extends the service life of the springs,” explains Christian Olsson, who developed the technique at Lesjöfors.
Controlling the process is crucial. For hot presetting to be successful, time and temperature must be carefully controlled during the various stages of the process. At the same time, this technique offers new opportunities – opportunities that Lars Blidberg expects will have a positive impact on Industrifjädrar’s sales.
“Hot presetting utilizes material in a more optimal manner, enabling fewer and lighter springs to be used in new ways,” says Lars Blidberg. “This increases our competitiveness, since it allows our products to be used in new customer applications.”