A luxury pen manufacturer was having trouble with its pen mechanisms. The springs did not give a consistent click and wore out quickly, which led to customer complaints and returns. This project was the redesign of that small compression spring.
The Problem
The original springs had a failure rate of 12% within the first six months of use. Our goal was to bring the failure rate under 3% while improving the feel of the click and the life of the mechanism.
Requirements
- Life: more than 500,000 click cycles without loss of performance.
- Consistency: every click should feel the same, from the first to the last.
- Environment: reliable function from dry indoor conditions to humid climates.
Our Solution
Material
We selected AISI 316 stainless steel for its fatigue resistance and its resistance to corrosion. It suits small precision springs and stands up to the repeated loading of a click mechanism.
Specifications
- Wire diameter: 0.3 mm, balancing flexibility and strength.
- Outer diameter: 2 mm, to fit the compact interior of the pen.
- Pitch: 1 mm, for consistent compression.
- Tolerance: ±0.05 mm, for uniform performance.
- Load: 1 N at half compression, chosen to give the right click feel.
- Surface treatment: passivation, to improve corrosion resistance.
The load figure matters most to the user. Too light and the click feels vague; too heavy and the pen is tiring to use. Holding that load within a narrow band on every spring is what makes the click consistent.
Results
- The failure rate over the same six-month period fell from 12% to 2.5%.
- Users noticed a more consistent and satisfying click.
What This Project Shows
Even the smallest component can decide how a premium product is judged. Careful specification of a spring only 2 mm across removed a source of returns and improved the feel of the whole pen.
If you need very small compression springs made to tight tolerances, send us your drawing through the contact page, or see our custom compression springs.
