Helical torsion spring torque testing

Case study

Close-ups of three helical torsion spring specimens being tested

Various torsion spring designs and specimen under test

Solution

Any of Mecmesin's software-controlled torque testers
EmperorTM rotates the spring to a predefined angle, continuously collecting torque and angular displacement data.

Benefits

To measurement of the stiffness, or spring rate, to ensure correct design specification.
Ulimate repeatability with software control and custom fixtures matched to the spring samples

Requirement

Spring-loaded components are used extensively in home and consumer goods: clothes pegs, clips and old-fashioned mousetraps; small doors and flaps on cameras or hi-fi equipment; large doors and closures such as those on garages or gates and in transport applications like vehicle luggage compartments.

Despite being termed ‘torsion’, and operating under torque loading, the spring itself is subjected to a bending stress when the ends rotate about its central axis, driven by the components attached to either arm (or leg).

The parts of an assembly, which are required to rotate in service, depend greatly upon the spring’s stiffness rating.

This determines if the assembly is fit for purpose and exhibits the correct level of resistance for ease of operation and quality feel.

Solution

A motor-driven test stand controlled by software rotates the spring to a pre-defined angle and collects the torque and angular displacement data continuously.

The software ensures repeatable testing in clockwise or anti-clockwise directions and protects against permanent set in the spring material.

Approaching the target load point from below and above, then averaging, minimises the effect of friction and hysteresis on the results caused by the contact between the spring coils.

The requirement to lie within specific torque range limits - when rotating the spring within its linear, elastic region - is immediately visible to operators through a clear PASS/FAIL indication.

In the smallest of torsion springs, used in precision applications, the frictional forces experienced by the coils may be highly significant.

The need is greatest to employ a test system which not only ensures that the spring’s axis remains aligned to within tight tolerances, but accurately measures the resulting very light torque values.