Improper Heat Setting Temperature

Too low fiber heat setting temperature leads to large shrinkage and dimensional instability, or too high temperature leads to fiber deformation and hardening with deteriorated hand feel. Heat setting is the key process for the orientation relaxation of fiber molecular chains and the perfection of crystallization — temperature and time determine the final shrinkage, crystallinity and mechanical property balance of the fiber. Fibers with improper heat setting continue to shrink and deform during subsequent processing and use, and the fabric dimensional stability is unqualified.

1. Mold/tooling factor: the temperature or time of the heat setting zone deviates from the process setting. 2. Mold/tooling factor: inaccurate measurement of the heat setting roller surface temperature. 3. Process parameter factor: the line speed change is insufficient to achieve the required residence time. 4. Cooling air field factor: the temperature, wind speed and uniformity of the side-blowing air or ring-blowing air determine the solidification and forming quality of the fiber — too fast cooling leads to rough surface and increased internal stress, uneven cooling leads to inconsistent thickness of individual filaments in the same bundle, and low wind speed leads to filament sticking and filament breakage; the air field parameters need to be precisely controlled.

1. Process parameter optimization and adjustment: regularly calibrate the heat setting roller temperature sensor. 2. Mold/tooling improvement and maintenance: select a reasonable heat setting temperature and time process pair. 3. Equipment inspection and system maintenance: match and adjust according to line speed changes. 4. Troubleshooting of spinning problems follows the sequence of "chips → temperature → metering → spinneret → cooling air". First check the chip dryness and IV value, then verify the temperatures of each section of the spinning box and pipeline, next verify the metering pump accuracy and pressure stability, further check the spinneret cleanliness and hole shape condition, and finally adjust the cooling air field parameters to make the wind speed and temperature evenly distributed. 5. Preventive management: establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or the 5Why analysis method to trace the root cause, and solidify the countermeasures as PFMEA control points. Establish a regular equipment maintenance system, and implement life management for key tooling such as dies/spinnerets/calender rolls/coating heads.

This problem is a typical manifestation of improper heat setting temperature in melt spinning. The core of the solution lies in the precise stability of the spinning temperature, the high-precision control of metering supply, and the optimized maintenance of the spinneret/cooling air field. It is recommended to start from chip quality and spinning parameters, and gradually troubleshoot to the equipment and component level.