To solve the problem of stiff yarn, the first step is to ensure the quality of POY: to reduce the problems of dry and uneven oil content in POY, timely track the status of components and side blowing conditions, and avoid the occurrence of uneven tension and insufficient false twisting in POY during the subsequent processing, which can lead to stiff yarn. 

The DTY processing process requires the equipment to be in good condition, and the first and second level rollers should not slip or deviate, so that the filament stretching is consistent; In terms of processing technology, it is required to have a moderate processing speed. Excessive processing speed can cause the filament to shake, and the friction condition on the false twister is unstable, resulting in stiff threads with intermittent breakage; On the filament, it is necessary to ensure that the filament is uniformly heated in a hot box to avoid the occurrence of filament channeling into the hot box, or the filament not entering the inlet or outlet of the hot box. These situations can cause insufficient heating of the filament and result in differences in twisting effect. In addition, it is necessary to strengthen online production status monitoring, eliminate various unstable factors, maintain good equipment condition, establish periodic component replacement or maintenance, and install online tension systems when conditions permit.