In order to qualify miniature springs, manufacturers of these systems rely on commercially available testers that are designed for large-scale springs (>0.5" diameter). Commercially available spring test systems lack sufficient force resolution or cyclic test capabilities for miniature-scale springs. Traditional spring testers work on the basis of compressing (or extending) a spring to a known deflection and recording that force value, then moving to the second known deflection and recording that force value. This is done manually by a user and has no capability of automation or fatigue.
A need existed for a spring tester with improved accuracy and precision that can serve as a means for product acceptance and inspection, while at the same time being capable of evaluating the cyclic degradation of springs such as the change in the spring rate over time, and how and when failure will occur.
A testing platform was developed specifically for miniature springs with improved accuracy and precision, along with the ability to evaluate spring reliability over its lifetime. The Miniature Spring Performance Tester consists of a testing device, control system, and operating system that automates spring testing, data collection, and analysis. A voice coil actuator is used to cycle the test spring through extension or compression force.
The system includes a linear encoder with a 1-μm resolution to act as a feedback loop that enables the system to make automatic adjustments, reducing operator time. The tester allows interchangeable use of force cells ranging from 10 g through 1 kg. Data obtained during testing is recorded using a bus-powered data acquisition device capable of 16-bit resolution, 250,000 samples/second, and a ±10 voltage range. This data can be used to determine the cyclic degradation of the springs over a lifetime.
Designed specifically for characterization of miniature springs, the tester evaluates static or fatigue characteristics, and automates the testing process.