The core yarn filament must be placed in the middle of the front roller output strand; due to the effect of twisting torque, the filament position should be slightly left of the center when spinning Z-twist core-spun yarn, and slightly right of the center when spinning S-twist.

1. The core yarn positioning should be correct  

The core yarn filament must be placed in the middle of the front roller output strand; due to the effect of twisting torque, the filament position should be slightly left of the center when spinning Z-twist core-spun yarn, and slightly right of the center when spinning S-twist.  

2. Appropriately control the core yarn tension and pre-draft multiple  

The rigid filament feeding type should be equipped with a yarn guide tension controller, and the filament feeding tension should be slightly greater than the drafting tension of the sliver. Sucssen recommends a general yarn tension of 20cN. The compact spinning tension is 50cN. The pre-draft multiple of the elastic filament feeding type is generally 2.5~4 times, which needs to be set according to the core yarn density, product strength and elasticity requirements. Generally, the greater the core yarn density, the higher the filament content, and the better the yarn strength, the greater the core yarn pre-draft should be, but excessive pre-drafting is prone to broken yarns. The actual pre-draft will vary for filaments of different materials, filaments of different linear densities, and the size of filament packages; excessive variation will result in differences in core yarn shrinkage and elasticity, resulting in defective products. The stability of the actual pre-draft directly affects the stability of the yarn quality and linear density.