Denim fabrics are after all fabrics made with yarns of varying fibre properties and manufacturing processes. The article explains the process of spun yarn manufacturing in the context of denim fabrics manufacturing.
Carding
“The card is the heart of the spinning mill”
“Well carded is half spun”
The tasks of the card
- Opening into individual fibres
- Elimination of impurities
- Elimination of dust
- Disentangling neps
- Elimination of short fibres
- Fibre blending
- Fibre orientation
- Sliver formation
The card is absolutely decisive for the quality of the denim yarns and for the efficiency of the production. It was possible to double the card production during the past 25 years.
The carding quality is decisively influenced in the areas of the cylinder, flat. Cylinder speed, clothing fineness and distance between cylinder and flat are deciding factors.
Monitoring and controlling the carding process is critical in ensuring minimal fibre damage. Instruments such as AFIS [Advanced Fibre Information System] can be used to generate information on processes that precede yarn manufacturing. The carding process is very aggressive and, if not adjusted properly, can reduce fibre length causing short fibre. This phenomenon is especially true in the new high-speed carding machines. If card flats are adjusted too close to the main cylinder, the nep and trash removal is improved, however, the result can also be a reduction in fibre length and an increase in short fibre content. Replacing a new cylinder wire or regrinding the wire will cause a temporary increase in short fibre content but this should return to normal in a relatively short time.
The measurement of short fibre content will have some variability due to the natural variation in raw cotton. The following guideline will give an idea of how much increase is significant.
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SFC(w) SFC(n)
Significant Increase >3% >6%
An increase in short fibre content less than these values are not significant and should not be considered a processing problem.
Causes of excessive wastage extraction carding
There are many reasons for which wastages are generated in the Blow room section. From the practical point of view extracted during the experiment, the following reasons are most important.
- Wider winch range (deflector blade) setting
- Incorrect delivery speed
- Guage in changeable points
- Amount of trash removed in Blow-room section
- Incorrect setting in note knives
Drawing Frames
Objectives of draw-frame
- To straighten the fibres in the slivers
- To make parallel the fibres in their sliver axis
- Hooks created in the card are straightened
- Through the suction, intensive dust removal is achieved
- To make the perfect blending of the slivers
- To reduce irregularities of fibre by doubling and drafting
- To improve the uniformity and evenness of the sliver