Machined spring provides required accuracy and lifeWhilst recently providing a product demonstration of the unique capabilities of the machined spring product, the experts at Abssac were asked an interesting question: "Would you be able to retrofit a spring now being used as a buffer spring in a fuel control system?"
The spring unit should compress and extend 2mm but deliver an accurate spring rate over a set lifetime. The current wire wound spring was not providing an accurate spring rate over time and each spring had to be rate tested and certified before fitting. Normal rate accuracies were ranging from ±15% and were not linear in rate.
The machined spring, as the name suggests, is machined from a single piece of material. This not only allows one, two, three or more spring elements to be machined into the single part but, due to the geometry of the coil, the spring rate is totally linear. In fact spring rate tolerance can be as good as ±1% if required with the machined spring.
After the preliminary discussion between the customer and an Abssac application engineer, a drawing of the concept spring was forwarded to be reviewed. A few minor changes were then needed, as the customer engineer looked into incorporating attachment designs into the single piece stainless steel spring. All other dynamic parameters could be improved on over the wire wound spring being used and a final configuration was then proposed.
Two test samples were sent to verify the installation and complete life testing. The machined spring supplied improved efficiency of the application, reduced parts inventory and each spring supplied was certified on rate so could be fitted straight into the application.
Solving this project has led to several other spring applications of the same physical configurations, but with varying spring rates and materials.
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