Flexible shafts are gaining importance. However, designing them for a specific application is very challenging.
Designing flexible shafts to stand up to the rigorous task of transmitting power where gear-drive; are not very successful or there is not enough space, is a tough job. And especially when the rpms are considerable. No doubt, flexible shafts transmit power of torque and have applications where no straight line is possible. At times there is a small misalignment to compensate or a transmission has to take place between moving components. In other cases, there is a need to control an operation in hazardous location or where the temperatures are high. For example, clean room applications or in hot environments like those found in plants that produce steel. For applications under situations mentioned above specially designed flexible shafts stand up to the task.
However, when it comes to designing flexible shaft; for such applications or even more diverse, 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, in which environment the flexible shaft has to run and what is the preferred turning direction.The length is not so important for the torque but plays a role for the torsional deflection and has to be considered for that application. In the flexible shaft design not all the parameters can be stretched in all directions. For example, if more torque is required, the minimum radius goes down and with it the flexibility, if the minimum radius can be made small the torsional deflection will go up, which is not admirable for a remote control cable.
Out of that reason in the flexible shaft business, two main design groups can be found. One is torque transmission shaft, mainly for higher speed, continuous speed, and pure torque transmission applications like speedometer cable or shafts for drilling applications. Second, are torsion stable flexible shafts for mechanical remote cables, with low speed and focus on low torsional deflection, like for slide adjustments for stationary cutting machines for instant. Besides these, there are special cable like flocked shafts, hollow shafts, shafts with helix wire and so on.
To influence the specification of the flexible shaft, the design, with the number of layers, the number of wires per layer or the dia of the wire, the material of the wire with higher or lesser carbon, different tensile strength and different plating, and the setting of the winding machines can be used.
To understand the influence of the machine setting it has to be under stood that the winding takes place with a high speed and by giving small-determined gaps the flexibility of the shaft will be influenced. And thus it is logical that the speed and gaps have to be exactly uniform. But the gaps are only one influential parameter; there are others like the tension of the wire, the spooling quality of the wire spools, the temperature of the operation and so on. Only an experienced operator can react fast to keep the quality at a high level.
|Posted : 8/30/2005|