Spinning fault

Spinning fault

1. Irregularity caused by raw material:

The natural fibres have variable varieties. They have no true fixed length, fineness, shape of cross- section, maturity, crimp, etc, which have effect on yarn properties specially evenness These variations are due to different rates of cell development due to changes in environmental conditions (nutrients, soil, and weather)
In man-made fibres, variations in mass/unit length occurs due to changes in polymer viscosity, roughness of spinneret orifice, variation in extrusion pressure and rate, filament take-up speed, presence of delustrant or additives, which can modify the particular shape and fibre surface geometry

cause of irregulity

2. Irregularity caused by fibre arrangement:

Textile fibres are not rigid. Their manipulation during conversion into yarn is an immensely complex combination of mechanical movement which usually requires some degree of compromise. The desirable results of relocating large number of fibres at high speed and arranging in well ordered form tend to be difficult. Fibres assembled into the form of a twisted strand constitute a yarn Fibres are not precisely laid end to end. And gaps are present between them. As a result of yams twist. fibres arrange in spiral form in a series of folds, kinks and doublings

3. Effect of fibre behavior :

Fibres shape directly affects yarn regularity. The fibre cross section, arrangement of fibre section and space between the fibres will vary from yarn section to section. Hence the mass of each section will differ. A thin place in yarn will have lower mass and less strength. In thin regions, yarn twist tends to be higher since resistance to deformation is lower

4. Inherent shortcoming of machinery:

In many engineering processes the by hand or machine and positioned with only a few thousands of an inch tolerance.
In spinning it is surprising how often the individual fibres are only negatively controlled at times they are carried forward by air currents or jostled along by surrounding fibres, or they are held in position by units from which the final product is assembled are positively friction and twist .

Fibre manipulation by rollers, aprons, gills, and other machine parts is hampered by fibre variation, and the machines can only be set to give the best results within the limitations imposed by the material. The drafting wave is one example of irregularity due to the inability of a drafting system to control each fibre. Where roller drafting is used, the distance from one nip to the other is greater than the length of the shorter fibres.

These short fibres 'float' in the drafting zone and move forward in an irregular but cyclical manner which results in the drafted strand having thick and thin places
The wavelength of this type of irregularity is about 2-5 times the mean fibre length but it is not necessarily constant for a particular strand. In addition to a varying wavelength, the amplitude of the drafting wave is also variable.

5. Mechanically defective machinery:

machines even in good condition produce irregular yarns, it is reasonable to assume that defective machine will increase the amount of irregularity implementation of an efficient maintenance system is essential if the level of irregularity is to be kept in bounds.
Machines drift out of adjustment, bearings become worn, components get damaged, and lubrication system clog and dirt works its way into the mechanism. fault rollers (top roller eccentricity) and gear wheels usually produce periodic variation.

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