Suhner Offers Flexible Shafts

An array of flexible shafts with end fittings.

An array of flexible shafts with end fittings.

July 27, 2012—

So you need to transmit a rotary motion where no straight line is possible? Or, you need to allow for some uncontrollable misalignment?  How about transmission taking place between moving components? What if you need to control something in hazardous locations where you cannot directly handle the application, such as high-temperature environments, under hazardous conditions or in clean room applications?  For all these challenges, functionally designed flexible shafts are your answer.

A flexible shaft is a very effective and cost efficient way to transmit rotary motion. In flexible shaft design, it is important to know how much torque has to be transmitted, how small the minimum radius for the shaft has to be, what RPM is required, the environment the flexible shaft will work in and the preferred turning direction. Length is not critically important for the torque but does play a role in torsional deflection and therefore must be considered accordingly.

In flexible shaft design, not all parameters can be pushed or stretched in all directions. If more torque is required, for example, the minimum radius goes down and with it the flexibility of the shaft. If the minimum radius can be made small, the torsional deflection will go up, which for remote control cable is not a good thing.

Related to the basic "reality" of flexible shafts, two main design groups emerge. First there are torque-transmission shafts, mainly for higher speed, continuous speed, pure torque transmission applications like speedometer cable or shafts for drilling applications. Second there are torsion-stable flexible shafts for mechanically remote applications, with low-speed and focus on low-torsional deflection.  An example is slide adjustments for stationary cutting machines. Beside these, there are special cables like flocked shafts, hollow shafts, shafts with helix wire and so on. We've provided some sketches showing some examples of special flexible shafts. Direct influences to the detail of flexible shaft specifications include: the number of layers, the number of wires per layer, the diameter of the wire, the wire material (with higher or lesser carbon, different tensile strengths, different plating), and the manufacturing process (settings on the winding machines).

Considering influences related to shaft manufacturing processes, it must be understood that winding is a high-speed process where gap settings will influence the flexibility of the shaft. The winding speed and the gaps must be uniform and controlled. Gap settings are a key parameter, but not the only one. There are others like the tension of the wire, the quality of the spooled-wire package, the temperature of the operation and so on.

Suhner Manufacturing, Inc.