Testing and managing raw material quality and consistency is critical to the profitability of a spinning mill. As the cotton price continues rising, and considering that the raw material is the largest cost in producing yarn, reliable instrument-based fiber quality measurements and benchmarks are the essential tools for controlling cost.
The International Cotton Advisory Committee (ICAC) reports that cotton prices continued to increase in February 2010 and will be higher than for the 2009-10 crop. The basis for this forecast is the dwindling stock-to-use ratio (reserves) around the world, not including China. This forecast will make smart fiber purchasing decisions critical for millowners as it is well known that the raw material cost can range from 40 to 80 per cent of total cost depending on the spinning system used and yarn counts/types spun.
Yet, in many parts of the world, cotton continues to be purchased on subjective parameters based on human judgment rather than solid and reliable instrument-based classing results. The bales of cotton are then managed and consumed by the mill 100 per cent on subjective parameters or limited instrument-based parameters. Still only 10 per cent of the lot to be consumed is tested, leaving to chance that there is no variation of properties within the lot. Once the bales are set in place for consumption by the mill, monitoring the quality of the fiber, through the preparation processes in yarn manufacturing, is typically minimal at best and done through subjective manual testing rather than using precise fiber testing instruments.
A spinning mill should know precisely the specifications required by the customer to spin the quality of yarn desired. These requirements are then used to make purchasing decisions for raw material. These same specifications should be adhered to in making decisions on the consumption and processing of the cotton bale inventory to minimize waste, maintain consistent production efficiency and deliver the customer’s end-product requirements. All of these factors can impact cost positively or negatively if not controlled.
To do this successfully requires testing and managing of the critical quality parameters of the raw material to be consumed by Uster HVI (figure 1), and monitoring of the in-process material from blowroom to roving by Uster AFIS (figure 2). Processes and fiber properties interact in delivering the required end-product performance and in optimizing cost.
Does it not make sense that processes and fiber quality should be managed every step of the way to make sure it is done successfully with the best possible profit margins? In today’s challenging business environment, this is a key question that should be considered by every spinning mill owner.
Fiber properties & processing
characteristics affected
HVI Fiber Property Processing Characteristic Affected
Strength >Yarn and Fabric Strength
>End Breaks in Spinning and Weaving
>Yarn and Fabric Fineness
>Yarn and Fabric Strength
Length >Nep Formation During Processing
>Formation of Pilling
>Yarn Evenness
>Yarn Imperfections
>Processing Waste
Length Uniformity/ >End Breaks in Spinning
Short Fiber >Yarn Evenness
>Yarn Imperfections
>Nep Formation During Processing
>White Specks/Shiny Neps
Fineness/Maturity >Yarn & Fabric Strength
>Product Appearance
>Processing Waste
>End Breaks in Spinning
>Processing Waste
>Textile Machinery Contamination/
component wear
Trash Content >Disturbances/Stops in Knitting
>Product Appearance
>Cotton Dust Levels
Color >Fabric Appearance (Barré)
>Fabric Neppiness
Neps >Waste
>Weaving Efficiency
U.V. Fluorescence >Fabric Appearance (Barré)
Figure 1. Significance of Uster HVI measured fiber properties and their impact on processing characteristics.
Significance of fiber properties, yarn preparation processes
Blow Room Carding Lap Winding Combing Drawing Roving
Neps Neps Length Length Length Length
Seedcoat Neps Seedcoat Neps Short Fiber Short Fiber Short Fiber Short Fiber
Short Fiber Short Fiber Maturity Neps Trash Neps
Trash Trash Neps Seedcoat Neps Maturity
Maturity Maturity Trash Neps
Length Length Maturity Seedcoat Neps
Figure 2. Important Uster AFIS measured fiber properties for yarn preparation process control.