Flexible Shaft Couplings

A flexible shaft coupling joins two shafts, maintaining rigidity in rotation and the transmission of torque while allowing enough flexibility to absorb the lateral misalignment that is inevitable when mechanical shafts from different motors are joined. Flexible shaft couplings protect equipment from premature wear and breakdown.

Manufacturers of Flexible Shaft Couplings

  • Zero-Max is a US provider of innovative motion control solutions, including its position as a world-class flexible shaft couplings manufacturer with high torsional stiffness and zero backlash shaft coupling solutions. Zero-Max’s flexible shaft coupling solutions including composite dics couplings, ServoClass shaft couplings, and their line of Schmidt Shaft Couplings designed to handle applications with challenging misalignments.
Flexible shaft couplings

Flexible shaft couplings & composite disc couplings

Mechanical equipment that requires a rotating shaft to be joined to another rotation shaft often need a flexible shaft coupling. Motors, gears and ball screws often manage shafting with use of multiple bearings. The purpose of the bearings is to hold the shaft straight and rigid while it’s rotating — which is necessary to avoid balance issues.

When two shafts are joined that aren’t in perfect alignment — either through misalignment, slightly non-parallel installation, or simply through design — the tensions on the shafts as they each try to maintain their original orientation stresses the bearings holding the shafts rigid. This causes additional wear on the parts, and leads to premature failure, up to and including the shafts themselves breaking.

Flexible Shaft Couplings, Torsional Stiffness, and Backlash

Torsional stiffness is one of the key qualities in flexible shaft couplings. Torsional stiffness is simply the coupling’s resistance to twisting force, and the amount of torsional stiffness needed varies by application. High torsionally stiff shaft couplings, also known as zero backlash couplings, have a greater precision in rotation; however, they are also less flexible.

Alternatively, torsionally flexible shaft couplings offer a solution to greater shaft misalignment issues and typically allow for some degree of backlash. In general, using a torsionally flexible shaft coupling compromises lower performance for the benefit of handling larger misalignments, preventing damage to motors, shafts, and bearings.

Shaft misalignment can occur in a number of different ways. You could have linear misalignment, in which cast the two shafts that the coupling is joining are both perfectly parallel to each other but don’t quite line up. More severe than this is angular misalignment in which the two shafts are actually set at slightly different angles to each other.

The most sever shaft misalignment is a combination of linear and angular misalignment of the shafts, which requires a very flexible shaft coupling that was specifically designed for such severe alignment issues.

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