Flexure

A flexure is a flexible element (or combination of elements) engineered to be compliant in specific degrees of freedom. Flexures are a design feature utilized by design engineers (usually Mechanical Engineers) for providing adjustment or compliance in a design.

Most compound flexure designs are composed of 3 fundamental types of flexure:

Since single flexure features are limited both in travel capability and degrees of freedom available, compound flexure systems are designed using combinations of these component features. Using compound flexures, complex motion profiles with specific degrees of freedom and relatively long travel distances are possible.

In the field of precision engineering (especially high-precision motion control), flexures have several key advantages. High precision alignment tasks might not be possible when friction or stiction are present. Additionally, conventional bearings or linear slides often exhibit positioning hysteresis due to backlash and friction. Flexures are able to achieve much lower resolution limits (in some cases measured in the nanometer scale), because they depend on bending and/or torsion of flexible elements, rather than surface interaction of many parts (as with a ball bearing). This makes flexures a critical design feature used in optical instrumentation such as interferometers.

Due to their mode of action, flexures are used for limited range motions and cannot replace long-travel or continuous-rotation adjustments. Additionally, special care must be taken to design the flexure to avoid material yielding or fatigue, both of which are potential failure modes in a flexure design.

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