1. In the blowroom process, the selection of opening and cleaning points and types of beaters should be reasonably made according to the characteristics of raw cotton:
(1) Opening and cleaning points refer to the machines in the blowroom line that provide strong opening and impurity removal. Increasing the number of these points enhances the opening and cleaning effect, too many can damage fibers, break impurities into finer particles, and increase neps.
When the raw cotton has fewer impurities, longer fibers, and lower maturity, fewer opening and cleaning points are preferred.
When the cotton contains more impurities, coarser fibers, good maturity, or comes in tight bales, more opening and cleaning points are required.
For cotton with high impurity content, high moisture, or tightly packed bales, pre-treatment is recommended.
For raw cotton with poor maturity, high impurity levels, fine and long fibers, it is better to have more opening and less beating.
(2) Selection of beater types: Common types of beaters include licker-in (angular spike), roller, three-wing, porcupine, pinned, saw tooth, and compound beaters.
- Licker-in (angular spike) beaters operate through free striking, achieving early trash removal with less fiber damage.
- Three-wing beaters perform grip-based striking, which is more intense and can damage fibers while offering less effective opening.
- Pinned beaters are used where fine opening is required, mainly for removing small impurities with good opening effect.
- Saw tooth beaters are widely used, and their opening and cleaning effect is generally better than pinned beaters, especially effective for medium to coarse fibers with more impurities.
2. Achieving a reasonable division of tasks between blowroom and carding based on impurity characteristics of raw cotton:
In fiber processing, the removal of impurities, short fibers, and neps mainly relies on the blowroom and carding processes. Since each has different abilities to remove specific types of impurities, tasks should be reasonably divided based on the type of contaminants in raw cotton.
Large, heavy particles such as cottonseed and seed cotton, which are loosely bound to fibers, should be mostly removed in the blowroom, following the principle of early removal, less fragmentation.
When the cotton contains a lot of impurities that are tightly adhered to the fibers (e.g., seed coat fragments with fibers, soft seed skins with fibers, neps, and entangled fibers), such impurities need to be broken into smaller pieces or even individual fibers in the blowroom for effective removal later. Therefore, they should primarily be removed at the flat strips of the carding machine.
According to the impurity content of raw cotton, the blowroom waste impurity rate, total trash removal efficiency, and sliver impurity status are controlled as shown in the table below:
Table
3. Reasonable Process Design in Blowroom Section
Principles of blowroom process design:
Appropriate feed quantity, fine opening with multiple bale breaks, more opening and less beating, early impurity removal with minimal fiber damage, sufficient blending, uniform feeding mechanism, anti-wrapping, anti-adhesion, anti-backflow, and anti-fiber entanglement.
4. Reducing Neps in Sliver
The formation of neps is not only due to the properties of raw cotton (e.g., fine and long fibers, poor maturity, high moisture regain, high workshop humidity), but also largely due to:
Feeding apron, pressing apron, and fiber entanglement on beaters
Excessive fiber height in the cotton box causing over-rolling
Beater speed too high or small clearance between beater and grid bar
Fiber entanglement in the ducts, low air pressure causing rubbing and entanglement
Sticky pressure rollers or roller wrapping
These causes should be addressed with enhanced attention and effective measures.
Carding Process
Carding is the key process for removing neps. Most neps and dead fibers originate from impurities and short fibers that cannot be removed during blowroom and must be removed during carding—especially at the flats and doffing areas.
1. Equipment Foundation Must Be Solid to Achieve “Five Sharp Points and One Precision”
(1) Dynamic and static balance of cylinder, doffer, and licker-in should be ≤ 0.05 mm
(2) Check and repair bearings to control shaft-clearance fit
(3) Ensure uniformity of top plate mounting surfaces (±0.02 mm height difference)
(4) Perpendicularity of curved rule working surface to inner plane
(5) Ensure the roughness and flatness of the feed plate, and cylindricity and straightness of feed rollers
Maintaining machine condition and ensuring the cylinder, licker-in, flats, doffer, and additional combing elements have sharp teeth and precise clearances is fundamental to reducing neps.
2. Reasonable Process Design
(1) Apply proper pressure to feed rollers to grip the cotton layer uniformly
(2) Reasonable speed settings:
Increase cylinder speed appropriately
Lower licker-in speed to control fiber damage and increase licker-in ratio
Adjust flat speed based on impurity levels: high impurity content needs faster flat speed; high trash content requires more removal by licker-in and less by flats; increase flat speed when production is high
Set doffer speed based on sliver linear density
(3) Reasonable setting of process clearances:
Feed plate to licker-in: based on fiber thickness and maturity, should be moderately wide
Licker-in to combing plate: small clearance improves combing but may damage fibers; usually 0.45–0.56 mm
Feed roller to feed plate: entrance clearance should be wide; outlet clearance affects fiber length and damage
Flats to cylinder: tight clearance increases neps and short fibers; fixed flats (especially rear fixed flats and pre-combing plates) should have wider gaps to reduce load and improve impurity removal; front fixed flats should be tighter for better fiber alignment
Cylinder to doffer: ~4″ to prevent fiber wrapping
Cylinder to front/rear cover plates: should be small and gradually decrease from infeed to outfeed to reduce floating fibers and neps
3. Better Control of Carding Waste
Control should be based on the impurity content in sliver and yarn quality. Licker-in waste should focus on removing large impurities with minimal fiber breakage.
4. Smooth Transport Channels
Ensure all fiber paths are smooth to reduce rubbing and nep formation. This improves parallelization and reduces neps during drafting.
5. Control of Temperature and Humidity
Proper control ensures stable production and fiber performance. High humidity leads to sticky cotton laps, poor opening, web sagging, end breakage, roller wrapping, and increased neps and dead fibers.
Blowroom: Relative humidity 58–62%, regain 6.5–7.0%
Carding: Relative humidity 55–60%, regain around 6.5%
Combing Process
The nep content in combed sliver decreases with increased noil (waste), according to the noil rate should be reasonably determined based on yarn count, quality requirements, raw cotton quality, card sliver nep/short fiber content, equipment condition, and cotton usage.
1. Reasonable Pre-Combing Process Setup
Feeding fibers in the correct direction is crucial. Even-numbered preparation stages help control fiber hook direction. This enhances fiber straightness and reduces back hooks, saving cotton as well.
2. Proper Selection of Combing Components
Use high-density cylinders or adjust needle arrangement to increase combing intensity. Ensure all parts are sharp and undamaged.
3. Reasonable Combing Process Design
(1) Prefer backward feeding to increase noil by 4–8% compared to forward feeding
(2) Proper feed roller positioning: as close as possible to lower nipper lip, ensuring sufficient pressure (e.g., 25×28 mm for long-staple cotton)
(3) Ensure good grip and steady clamping pressure, with appropriate closing timing
(4) Reasonable combing clearance: tighter is better for quality, but avoid damaging the cylinder
Arc plate position depends on fiber length and separation timing
Use 2 graduations for short feed of fine-staple cotton; 1.5 for long-staple
(5) Proper top comb height and in-out clearance:
Smaller clearance ensures top comb acts near the separation point, improving combing
Larger clearance allows deeper penetration and longer combing time, increasing waste removal, but excessive depth may affect fiber lifting
4. Fully Utilize Waste Removal System
(1) Improve brush cleaning efficiency; optimal surface speed ratio between cylinder and brush: 1:5.8 to 1:6.8
(2) Adjust suction airflow to avoid excessive suction carrying short fibers or dirt into the web, affecting machine cleanliness
IV. Drawing and Roving Processes
(1) For carded yarns, use positive draft in drawing to improve fiber parallelization and reduce hairiness
(2) For combed yarns, avoid over-drafting or over-refining to prevent excess hairiness in later processes. Use smaller trumpet mouths and larger roller pressures; roving front rollers can be slightly advanced to enhance false twist and reduce hairiness.
V. Ring Spinning Process
Focus on reducing yarn hairiness to prevent fiber entanglement:
(1) Select appropriate ring and traveler types, control service life, and maintain proper cleaning clearance to prevent fiber wrapping
(2) Adjust balloon shape to prevent contact with yarn guide and bobbin
(3) Use soft front rollers and slightly forward roller positioning to reduce the untwisted triangle zone
(4) Use bundling devices (condensers) to reduce hairiness—though this requires stricter production management
Winding Process
(1) Use low spinning tension (without causing soft bobbins)
(2) Use lower winding speed
(3) Avoid friction between suction nozzle and yarn package; maintain proper contact pressure
(4) Ensure smooth yarn paths
Temperature and Humidity Control
Good workshop climate control is essential for stable production and quality.
Excessive humidity leads to cotton lap sticking, poor combing, web sagging, end breaks, beater/roller wrapping, cylinder fouling—all increasing neps and dead fibers.
Recommended humidity:
Blowroom: 58–62% RH, 6.5–7.0% regain
Carding: 55–60% RH, ~6.5% regain
Conclusion
Nep control is a comprehensive and systematic process that runs through all spinning stages, starting from raw cotton selection. The carding and combing are the core of nep control, other processes must not be neglected. Only by ensuring every step is well-managed can product quality be consistently guaranteed.
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