Main flexure characteristics are: precision, repeatability, and no friction. Similar to plain or rolling bearings, flexures are joints, connecting solid members which permit relative motion in some directions while constraining motion in others.
Absence of solid friction
Plain or rolling contact between solids inevitably generates friction which alters the joint’s functioning. Friction dissipates energy, provoking mechanical hysteresis. At low speed it causes a halting motion due to the “stick & slip” phenomenon which limits the resolution of the movements. Friction is at the origin of wear and flexures are free from any solid friction. It remains solely at the internal friction of matter which is practically negligible.
Absence of wear
Wear reduces the precision of plain and rolling bearings because it alters their geometry and increases their mechanical play. Moreover, it is the principal factor limiting their lifetime. Flexures do not suffer from these drawbacks and therefore, their lifetime is only limited by potential material fatigue. Good design maintaining stress below the fatigue limit allows Mecartex to offer nearly a lifetime guarantee.
Absence of mechanical play
To reach high precision, plain and rolling bearings often require complicated play compensation. By definition, flexures have no play.
The more rigid the mechanical structures of machines are, the more precise they are statically (when external loads are applied) and dynamically (when vibrations occur). The rigidity of rolling bearings depends on the pressure of rolling elements on top of a rolling surface. With small bearings, the small radiuses of the rolling elements limit rigidity. Well designed flexures can be much more rigid than rolling bearings
Plain and rolling bearings are made of many mechanical parts which need to be assembled. This assembly increases their bulkiness and reduces their construction precision. Wire-electro discharge machining allows Mecartex to manufacture very complex flexible structures monolithically, thus providing high compactness and precision.
The wear and required lubrication of plain and rolling bearings frees particles of matter which can pollute the air of clean rooms. In addition, when used in dirty environments, dust can easily hinder or even block these bearings. Flexures are perfectly clean and are not affected by dirt.