Udo Schweizer’s Texturing Pages

Why do we produce textured set yarns:
To give synthetic yarns special properties such as low stretch, high bulk and volume and the touch of natural fibers. Set yarn is required especially for some knitting applications.

The set yarn texturing principle:
For this process machines with two heaters in the yarn path are needed. The first part of the machine is identical to the stretch yarn process described in the single heater page. All set yarn machines are working on the same principle. The schematic below shows the most important steps in the manufacturing of set yarn.

POY, which stands for Partially Oriented Yarn, is now the standard feed yarn for the texturing process. It is a continuous filament yarn spun at a speed, which is for example with polyester around 3200 m/min.
Shaft 1 is the input feeding device for the POY. From here the yarn is fed to Shaft 2. When POY is fed into the machine, the yarn has to be drawn. The speed of shaft 2 is always higher by the factor of the necessary draw ratio for the particular yarn and process. The yarn is simultaneously twisted and drawn. The twisting is done with a friction device, such as a set of rotating friction disks. But there are other devices. After Shaft 1 there is a yarn heater, which heats the yarn to a temperature where it can be thermo-set. Adjoining the heater is a cooling plate, which must cool the yarn to a substantially lower temperature in order to permanently thermo-set the twist. The highly stretchable yarn is now relaxed just enough between shaft 2 and shaft 3 to allow the filaments to crimp slightly. In this condition the yarn is thermo-set once more. This process reduces effectively the sometimes undesirable high stretch. The yarn released from Shaft 3 is a voluminous bulked yarn with properties very similar to natural fibers.