Springs often break due to metal fatigue beginning with a tiny flaw and then progresses to a full fracture separating the spring into multiple pieces. Often the metal hardness is wrong, the surface finish is poor, or there is some other imperfection from manufacturing which sets up the failure. If we could see the fracture faces of the end of the spring, it could tell more.
When springs fail in the equipment I work on, often we have to analyze the root cause. It's really interesting. It may be that the diameter of the spring was too small for the stresses imposed with the loads and speed of movement; therefore there was a high number of failures. That might be why the manufacturer went with a larger, less highly stressed external spring on the new design.
Comes to the Rescue!
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