A well-written spring specification saves time, reduces cost, and ensures the delivered parts match the design intent. Yet many European procurement teams and design engineers submit spring drawings with incomplete or unrealistic requirements. This guide outlines the essential parameters to include when requesting a quotation for a non-standard precision spring.
1. Wire Diameter and Material Grade
Specify the exact wire diameter and material. Instead of simply writing “stainless steel,” use the specific grade such as AISI 302, 304, or 316. If the application involves electrical contact, beryllium copper C17200 is common. Always note if REACH and RoHS compliance is required.
2. Spring Dimensions
For compression springs, provide outer diameter, free length, and total coils. For extension springs, include the hook style and opening size. For torsion springs, specify the leg angle and leg length. Importantly, indicate which dimensions are critical and which can have wider tolerances. Over-tolerancing non-functional features unnecessarily increases cost.
3. Force and Spring Rate Requirements
This is the most frequently neglected section. Do not just provide a spring rate; specify the target force at a specific compressed or extended length. For example: “2.5N ±8% at 6mm compressed height.” This allows the manufacturer to design the spring to meet functional needs rather than purely geometric targets.
4. Environmental and Life Requirements
State the expected operating temperature range, any chemical exposure, and the required cycle life. A spring for a laboratory instrument working at room temperature needs a different material and treatment than one inside an automotive sensor cycling from -40°C to 125°C.
5. Quantity and Lead Time
Be realistic about volume. At Tingfeng Hardware, we accept orders from 200 pieces, but pricing is directly tied to batch size. Indicating the approximate annual usage helps us recommend the most cost-effective tooling strategy.
Conclusion
A complete specification helps us provide accurate quotations and deliver parts that perform. We welcome European engineers to contact us with their spring requirements—even at the early concept stage—for DFM feedback.