Medical Micro Compression Spring: 0.2mm Wire, ±5% Force Tolerance, 5M-Cycle Fatigue Verified
The spring inside a minimally invasive medical device is the least visible part of the system - and the one that cannot fail. A 0.2mm wire coiled into a 1.5mm outside diameter spring must hold its force through 5 million compressions. The tolerances on the drawing are fixed; everything in manufacturing is live - material, coiling, tempering and sorting all have to line up.
Project Background & Challenge
A medical device manufacturer developing a new drug delivery system needed a micro compression spring: 0.2mm wire, 1.5mm OD, 8mm free length, working force within ±5%, 5-million-cycle fatigue life, and material documentation for medical contact use. They had been buying from an overseas supplier with 8-week lead times - one trial iteration took two months.
Three challenges: the wire is too thin for forgiving coiling (loose coils are the norm, not the exception); the force tolerance is tight enough that only 100% sorting guarantees it; and fatigue life depends on stable process parameters, not a lucky sample.
BQUQ Process Solution
Coiling & Tempering
We coil on small-arbor precision spring machines with closed-loop tension control to eliminate loose coils and uneven pitch, then temper at controlled temperature to stabilize free height and force. Incoming wire is re-verified for diameter and tensile strength - good machines cannot fix bad material.
100% Force Sorting
Every finished spring passes through an automatic sorter that groups by force value; anything outside the tolerance band is rejected on the spot. Fatigue life is verified per batch on a 5-million-cycle test with a life-curve report.
Key Specifications
| Item | Specification |
|---|---|
| Material | 304/316L stainless, 17-7PH (per drawing) |
| Wire diameter | φ0.1-0.5mm |
| Outside diameter | From φ1.2mm |
| Force tolerance | ±5%, guaranteed by 100% sorting |
| Fatigue life | 5M cycles, batch sampling with report |
| Volume | 100K-piece level deliveries; trial iterations in 2-3 weeks |
| Inspection | 100% automatic force sorting + profile projector + fatigue tester |
| System | ISO9001:2015, material certificates with shipment |
Quality Control & Delivery
Material lots are traceable; every batch ships with material certificates and a force-distribution report. A 30,000-piece trial was delivered in 3 weeks, then moved to volume after the customer's build validation. Subsequent revisions only need coil parameter changes - new samples within 48 hours.
Related Products & Resources
To see more parts in this category and how we scale them, browse the Compression Springs category page, or these related products:
Related Q&A: Which Spring Wire Is Better: Music Wire or Oil-Tempered Wire?. More manufacturing Q&A is in our FAQ Center.
For our capabilities, equipment and quality system, visit About BQUQ and Factory Strength.
FAQ
Can you really coil 0.2mm wire?
Yes - our smallest production coils use 0.1mm wire. The key is closed-loop tension control on a small-arbor machine plus controlled tempering. Thin wire is rarely a coiling problem; it is a tempering temperature problem.
How is a ±5% force tolerance guaranteed?
Two gates: stable coiling parameters and 100% automatic sorting of finished parts. Anything out of band is rejected - every delivered piece is inside tolerance, with a force-distribution report included.
What documentation do you provide for medical use?
Material certificates and RoHS/REACH test reports ship with every lot, and material batches are fully traceable. Quality runs under ISO9001:2015; specific medical-system requirements are handled per the customer drawing and agreement.
