A Sweden-based medical technology company was developing a new handheld diagnostic monitor intended for point-of-care use in clinics. During the final prototype phase, they encountered a critical issue: the standard, off-the-shelf battery contact springs they had sourced from a catalog distributor were too large. The bulky springs prevented the device enclosure from closing properly, and the inconsistent contact force caused intermittent power interruptions during device startup.
The Challenge
Part Description: Custom miniature battery spring contact with a specific deflection range.
Geometry Constraint: The contact had to fit within a 4.2mm vertical space, yet deliver a minimum normal force of 60 grams.
Quantity: Only 800 pieces were needed for the initial pre-production validation run.
Timeline: The client needed parts within 5 business days to stay on schedule for regulatory testing.
Our Solution
Given the small volume and urgent timeline, producing a full progressive stamping die would have been both cost-prohibitive and too slow. Instead, our engineering team proposed a hybrid manufacturing approach:
1.Wire EDM Prototype Tooling: We machined a simple single-station bending die from pre-hardened steel using wire EDM. This allowed us to form the complex bend geometry without waiting for a multi-station progressive die.
2.Material Selection: We recommended Phosphor Bronze C51000 strip, pre-plated with a thin layer of tin. This provided the required spring force and eliminated the need for post-plating, saving 2-3 days.
3.Manual Assembly for Wire Lead: The contact included a small solder tab. For this low-volume run, we attached the tab using a precision resistance welding process rather than designing an automated feed mechanism.
The Outcome
Within 4 business days, we manufactured and shipped 850 precision spring contacts (including 50 spares) to the client's facility in Stockholm. The parts fit perfectly within the enclosure, and the consistent 60-gram contact force ensured reliable device startup every time. The client was able to proceed with their regulatory testing without delay.
Value Delivered
This case highlights Tingfeng Hardware's ability to support European medical innovators even at very low volumes. By employing flexible tooling strategies and a pragmatic approach to assembly, we bridged the gap between prototype needs and production realities. The Swedish client has since returned for a follow-on order of 5,000 pieces, this time utilizing a more efficient progressive die—but only after the design was fully validated with the initial small batch.