Basic knowledge of extension spring

1.What is the extension spring

Extension spring is a spiral spring that bears axial tension. Generally, tension spring is made of circular section material. When not under load, the coils of the tension spring are generally tight without clearance. The working principle of the extension spring is opposite to that of the compression spring, which has a reverse effect when being stretched. The most common type of extension spring is the relative angle of the hook from 90 ° to 180 °.

2. Classification of tension springs

Ultra light load type, light load type, medium light load type, medium load type, medium heavy load type, heavy load type and extended heavy load type

3. Extension spring material

SWP-A/B (piano wire) service temperature: normal temperature (0~40 ℃)
SUS304-WPB (stainless steel) service temperature: – 10~100 ℃

4.Application field

Medical, furniture, hand tools, switchgear

5. Features

Tight connection, uniform and beautiful surface
High plasticity, good fatigue strength and corrosion resistance
Good formability and even rebound
Good reliability, high cost performance

6.Key points of tension spring selection

Load: select the size according to the working limit load in the sample book

Material: select the material according to the actual use temperature and corrosion resistance. 304 stainless steel has good corrosion resistance, high tensile strength of piano wire, and good toughness and elasticity

Tolerance: select inner diameter datum type or outer diameter datum type according to actual use requirements
Work schedule: refer to the work schedule in the sample book or communicate with the corresponding technical personnel

7. Extension spring maintenance

Regularly spray anti-rust oil (1-2 times a month)
Regularly check whether the extension spring catches foreign matters and clean the surface dust

8.Common problems and analysis

1. 304 stainless steel material may have some weak magnetism due to processing technology, and the magnetism is not easy to eliminate
2. The hook part of the tension spring is relatively fragile, and collision should be avoided
3. When calculating the load, the Z load shall prevail