By Gopinath Rout
Yarn quality is crucial for achieving happy customers. It directly affects the look, feel, and durability of the final fabric. Uneven yarn with neps (tiny knots) and thick and thin spots can ruin the appearance of the fabric. That’s why spinners, those who make yarn, need to be very focused on yarn quality.
In today’s world, getting the desired yarn quality is essential. Here are some key factors that spinners need to consider to achieve this:
- Raw Material Properties
- Process Parameters
- Process Control.
- Environmental Conditions
- Machine Maintenance.
- Consistent Scheduling
- Waste Minimization
Raw Material Properties
The properties of cotton, polyester, and viscose fibres directly affect the quality of the yarn produced. These fibre characteristics determine how strong, soft, and breathable the final yarn will be.
| Cotton Fiber | Polyester Fibre (Staple) | Viscose (Staple) |
| Micronear(MIC) | Diner | Liner density |
| UHML | Type | Staple length |
| ML(MM) | Tenacity | Tenacity conditioned |
| G/TEX | Elongation | Elongation conditioned |
| RISI(SCI) | T10 | Moisture regain |
| UI | Dry heat shrinkage | Finish oil |
| MATURITY | Crimp | ISO brightness |
| SFI % | Crimp removal | Over-length |
| RD VALUE | Oil pick up | |
| +B | Crimp stability | |
| COLOR GRADE | Fuse fibre | |
| Moisture % | Over-length fibre | |
| Sfc (by number)% | MLF | |
| Trash % | Avg cut length | |
| Elongation | L -colour | |
| Neps /g (including scn) | B – colour | |
| 5.0% length | Dyeability | |
| Moisture |
Process Parameters
This section outlines the key process parameters that need to be adjusted based on the desired final yarn characteristics (denier/count) and the properties of the raw material.
Factors Influencing Parameter Settings:
- Final Yarn Denier/Count: The fineness of the final yarn dictates adjustments to various machine settings like machine speeds (beater, fan, cylinder, etc.) and feed and delivery speeds.
- Machine Coordination: Settings between interconnected machines, particularly in the blowroom and carding stages, need to be carefully coordinated for optimal fibre processing.
- Fibre Control: Maintaining a consistent distance (gauge) between processing elements is crucial for yarn quality. This gauge is determined by the fibre span length and a 5% buffer to ensure proper fibre handling throughout the process (blowroom to ring frame).
- Drafting Strategy: Break draft, the initial separation of fibres, significantly impacts the preparation of the sliver/roving for subsequent drafting stages. The optimal break draft depends on the desired yarn characteristics.
- Spacer Settings: Adequate spacing between processing surfaces, particularly during the main drafting zone, is essential for effective fibre attenuation. This spacing is determined by the fibre micronaire value (mic) and the final yarn count.
- Hank Organization: The targeted weight per unit length (grams per metre) at each processing stage (blow room to ring frame) is referred to as Hank organisation. This is crucial for efficient fibre attenuation and depends on the fibre mic and the final yarn count.
- TPM: TPM significantly influences yarn quality factors like unevenness (CSP), strength (RKM), fabric handle, and dye uptake. The optimal TPM setting is determined by the fibre length, mic, and speed settings of the spinning frame and ring frame.
In essence, all these process parameters are interconnected and need to be optimised based on the specific raw material characteristics and the desired final yarn properties.
Process Control
- Importance: Consistent yarn quality is crucial in spinning mills. Process control ensures this consistency by monitoring and adjusting various parameters throughout the production process.
- Monitoring Methods: Different processes require monitoring specific quality parameters. These parameters are checked frequently depending on the product’s desired quality. Checks can be done physically or digitally, providing real-time data for corrective actions.
- First-In, First-Out (FIFO) System: This system ensures that materials are processed in the order they arrive, minimising quality variations due to storage time.
Department-Specific Control Measures
Each department has its own process control procedures to achieve the desired yarn quality:
- Process control definition: It’s the practice of ensuring that materials flow through the production line while meeting specific quality standards.
- Corrective Actions: Any deviations identified during process checks require immediate corrective actions to prevent quality inconsistencies.
Humidity Control
Humidity significantly impacts yarn quality and machine performance. Maintaining consistent humidity levels is essential for:
- Controlling Machine Function and Quality Variations: Fluctuations in humidity can affect yarn properties like CSP (Unevenness), NEPS (Neps and imperfections), and cuts in cones. Additionally, proper humidity control ensures consistent moisture content in the sliver and roving, minimising invisible yarn loss.
- Balancing Supply and Return Air: Uneven air distribution can create pockets of varying humidity, affecting yarn quality and fly generation (loss of fibres). Maintaining proper air balance is crucial.
Compressed Air Quality and Quantity
- Clean and Dry Air: Compressed air supplied to spinning machines must be free of oil and water to prevent machine problems and ensure yarn quality.
- Adequate Airflow: Maintaining the desired air pressure and quantity is essential for proper drafting zone functionality and overall machine performance. Inadequate air can negatively affect yarn quality.
Maintaining Optimal Machine Performance
- OHTC Functioning: Proper nozzle direction, placement, cleaning, and suction are vital for efficient waste disposal and optimal machine operation.
- Scheduled Maintenance: Regular maintenance is crucial for achieving consistent results. This includes:
- Ring Spinning: Monitoring spinning geometry for quality and productivity, cleaning, oiling, greasing, and replacing worn parts by skilled personnel.
- Material Flow: Ensuring clean passage for material flow without damage to prevent yarn imperfections.
- Machine Parts: Maintaining the integrity of machine parts like cots, aprons, teeth, and rolls.
Cleanliness Throughout the Process
Maintaining a clean environment throughout the production process, from blow room to ring frame, minimises:
- Yarn Imperfections: Cleanliness reduces neps, cuts, thin places, and thick places in the yarn.
- Waste Management: Regular cleaning of waste suction systems and material passageways is crucial, whether automated or manual.
- Drafting Zone: This critical area needs constant cleaning to prevent fly and fluff accumulation, ensuring consistent yarn quality.
Waste Consistency for Optimal Recovery
Maintaining consistent waste percentages across machines for the same raw material ensures consistent product quality and optimal yarn recovery.
Importance of Housekeeping
A clean and organised work environment fosters better quality control and overall mill efficiency.
Conclusion
High-quality fabrics rely on high-quality yarn. Implementing these process control measures throughout the spinning process ensures consistent yarn production, paving the way for creating beautiful and desirable fabrics.
