When fabric travels from one section of a machine to another, such as from an oven to a winder, it is sometimes necessary to install a machine called a “dancer” to accurately control the web tension between the machine elements. Tension is measured in pounds per linear inch of web width. A lightweight or lightly bonded fabric would break apart at the higher tensions used on a heavy or tightly bonded fabric. The dancer enables the operator to dial in the web tension.
In the dancer shown below, you can see that the last roll the material goes under as it exits the machine is the actual dancer roll. The motor on this dancer drives a set of nip rolls that pull fabric into the dancer. The dancer roll is usually made of aluminum or carbon fibers for light weight. This reduces the inertia of the roll and enables it to respond quickly to variations in web tension. You can see that the dancer roll is mounted on an arm that pivots with the other end of the arm connected to an air cylinder. By setting the air pressure in the cylinder, the operator is setting the tension on the fabric. If the fabric tension changes, the dancer roll will move vertically. The shaft which is the pivot point is connected by a sprocket and chain to a trimming potentiometer that controls the speed of the machine following the dancer. The electrical adjustments are such that the dancer roll maintains itself in the center of its range of vertical travel.