1 Air Volume of Negative-Pressure Fan and Negative Pressure of the Suction Tube
The negative pressure inside the suction tube is the most direct and critical factor governing the quality of compact spun yarn. Flower buildup inside the plenum chamber of the negative-pressure fan also exerts a major influence on tube negative pressure. During routine production, accumulated fly must be removed promptly to sustain stable negative pressure. Practical tests and production data show that compact spinning negative pressure should be maintained within 24–30 mbar. Insufficient negative pressure raises end breakage rate, increases hairiness, lengthens hairiness fibers and widens the unevenness of hairiness. Under identical temperature and humidity conditions, when negative pressure runs at 24–27 mbar, the pressure difference between the head and tail of the machine is roughly 1.5–3.5 mbar, bringing about around 30% difference in yarn hairiness. Production experience indicates that a 4.2 kW negative-pressure fan suits a 1008-spindle spinning frame, while a 2.4 kW fan is suitable for a 512-spindle frame. Appropriately raising fan speed can reduce the head-to-tail pressure gradient and minimize its adverse impact on yarn quality. During each overhaul, run the negative-pressure fan to suck out and clear fly trapped inside the suction ducts.
2 Motion of the Fiber Strand on the Suction Tube
The running condition of the fiber strand on the suction tube is extremely important for yarn evenness. With normal negative pressure, the strand travels from the front roller onto the suction tube and moves along it in a relatively straight state while continuously converging. Nevertheless, its motion may be disrupted by a variety of factors.
In actual production, excessive cradle pressure, static buildup, defective roller surface and insufficient suction tube pressure can make the strand sag or sway sideways within the “uncontrolled zone” between the roller and suction tube, which markedly deteriorates yarn evenness. Therefore, cradle pressure for compact spinning should be set on the low side. It is necessary to suppress static accumulation, keep roller and top roller surfaces smooth to prevent wrapping and sticking, and maintain rated suction pressure. Meanwhile, anti-static lattice aprons with a proper mesh count are recommended.
3 Influence of Workshop Temperature and Humidity
Owing to air intake and exhaust in compact spinning, obvious temperature inconsistency emerges between the machine head and tail, and this disparity varies with seasons: the temperature gap is about 2–4°C in winter and 3–6°C in summer. Temperature and humidity strongly affect yarn hairiness. Field measurement reveals that hairiness and neps at the machine tail are approximately 40% higher than those at the head, as shown in Table 1. Stable ambient conditions and reduced spatial variation in temperature and humidity are essential for quality improvement.
4 Cradle Pressure
Cradle pressure bears a direct impact on yarn quality. Excessive pressure shortens the service life of the front top roller, causes roller concave wear and may generate roller mechanical waves. A front top roller normally lasts around two months; under overpressure, it tends to lose reliable control over roving after only one and a half months, triggering a sharp rise in end breaks. For compact spinning, cradle pressure should not be too high; the recommended range is 160–180 N per double spindle.
5 Effects of Spinning Parameters on Yarn Quality
The floating zone is vital to yarn performance. Floating zones across all spindles must be uniform. The pressure bar shall be properly positioned without rubbing against the front roller or the long apron. A rearward-shifted pressure bar enlarges the floating zone, weakening fiber control and possibly abrading the long apron. If placed too far forward, it pushes the roving upward and renders the pressure bar ineffective; rubbing against the front roller will introduce roller mechanical waves. In production, the forward offset of the top roller is preferably 2–3 mm and shall not exceed 3 mm. Excessive offset easily creates a reverse wrapping arc, degrading yarn quality and increasing breaks. An overlarge floating zone in compact spinning may also let the front top roller press down on the lattice apron. As the strand swings laterally along the suction slot within the traversing range, yarn quality suffers.
Well-distributed draft ratios also help upgrade yarn quality. When selecting draft multipliers, it is inadvisable to pursue superior evenness and low neps blindly. Continuous increase of draft will raise the long-term unevenness of the yarn. For compact spinning process development, beyond the critical draft, the back draft can be moderately increased together with a proper rise in spindle speed to lift output and economic returns.
6 Conclusion
Yarn quality optimization is sophisticated, affected by a wide array of variables. Comprehensive consideration is required during process tuning to achieve optimum yarn quality.
一句话英文概括
Stable suction pressure, controlled strand movement, balanced workshop climate, properly set cradle pressure and optimized spinning parameters jointly deliver high-quality compact spun yarn.
SEO keywords (American English)
compact spinning, compact yarn quality, negative pressure fan, lattice apron, floating zone, cradle pressure, yarn evenness, yarn hairiness
Post time: Nov-06-2026