ACY air covering yarn, elastic yarn, and spandex are parallelly ply-coated and introduced into a special network nozzle, and the compressed air with a set constant pressure is intermittently inflated and deflated through the nozzle. The air power adheres the nylon DTY elastic yarn to the spandex to form a uniform network of adhesion points. This process is called two-step spinning; air covering yarn can also be directly produced on the elasticizing empty bag integrated machine using POY, which is called one-step spinning. One-step spinning is suitable for large-scale production and has more price advantages. Empty bags can be used for various textile products and are the main category of deep processing of elastic raw materials. After being woven into fabrics, they have good elasticity, a fluffy, soft, velvety feel, and easy coloring.

SCY mechanically covered yarn is to wind the outer layer of the covered yarn (such as nylon stretch yarn, etc.) onto an aluminum tube in advance, fix the aluminum tube with the yarn on the rotating spindle, and set the wrapping twist and spandex draft ratio. After the yarn wrapping machine is started, the spandex passes through the empty tube in the center of the spindle and is combined with the yarn head on the aluminum tube to be introduced into the drafting roller. As the spindle drives the aluminum tube to rotate, the outer layer of yarn is spirally wound on the spandex to form a tight, mechanically covered yarn. Machine bags are widely used and can be made of DTY, HOY, FDY, cotton, linen, viscose filament, etc. Compared with empty bags, nylon wrapped with spandex is tighter and more secure, and the twist can be very high. After being woven into fabrics, the fabric texture is clearer, the fabric appearance is high-grade, and the fabric feels softer and has less hairiness, so it is wear-resistant and anti-pilling, and is an ideal material for elastic fabrics and fabrics.

DTY is a stretch yarn formed by POY filaments after being stretched by a stretching machine. The yarn is elastic, soft to the touch, and fluffy in appearance. DTY can be processed into differentiated yarns such as machine-wrapped, empty-wrapped, plied, and composite yarns. The specifications range from 12d to 70d, with f numbers (6 to 68). 70d/48f and 50d/48f and their plied yarns are mainly sold to seamless underwear manufacturers.