Monday, April 12, 2021

hollow spindle spinning method (wrap spinning process)

Hollow spindle spinning method ( wrap spinning process ):

Wrap spinning process:

The wrap spinning is a process in which a drafted strand of parallel fibres is wrapped by either surface fibres protruding from the fibres strand or by a continuous filament or filaments. The wrapping filament imparts coherence and strength to the resulting yarn in the wrap spinning process.
The high-quality specific yarns with a wide range of applications are produced in the wrap spinning process.

The wrapped yarn consists of two components. The first component contains a drafted strand of staple fibres in the yarn core. The second component is a filament which is wrapped around the drafted fibres strand.
The hollow spindle spinning method is most commonly used to produce wrapped yarn.

Hollow spindle spinning method:
The complete mechanism of the hollow spindle spinning method can be divided into four sections:
1 - Roller drafting mechanism.
2 - Hollow spindle.
3 - Pair of delivery rollers and package building mechanism.
Roller drafting mechanism:
The drafting roller mechanism consists of a series of rollers. These drafting rollers reduce the linear density or weight per unit length of the fibre strand getting processed.

The 3 or 4 roller drafting assembly allows selection of either the clamping point or draft methods with a draft range of 5 - 59. Fibre length between 50 - 220 mm can be processed effectively. Electronic monitoring used to identify faults and improves yarn quality. Special features of the drafting assembly include self-alignment of the spinning triangle to the centre of the spindle and continuous suction at the draft rollers, which eliminates roller lapping and assist in self-cleaning in the spinning zone. Pneumatic threading is an optional attachment to the hollow spindle and speeds up the operating time. A photoelectric cell monitor equipped to detect end-breaks to stop the spindle when a break occurs.

Hollow spindle mechanism:

The hollow spindle is designed as a false twisting assembly. The fibre strand does not pass directly after entering the vertical spindle instead, shortly after entering the spindle; this strand is led out again and back around the spindle with a wrap of about one-quarter of the spindle periphery. In this way, as the spindle rotates, the strand is provided with a twist between the drafting arrangement and the head of the hollow spindle. These turns of twist are cancelled out again in the spindle head in accordance with the false twist principle. This twist prevents the strand from falling apart in the length prior to filament staple fibres wrapping with filament.
A wrap spun yarn consists of a non-twisted parallel bundle of staple fibres held together by helically wrapped filament as shown in Figure 2. The proportion of the filament in the yarn is about 2 - 5%. Due to the helical wrapping of the filament and radial pressure, necessary cohesion between the individual staple fibres is improved. This imparts desired strength to the yarn. The number of wraps per unit length in a standard PL yarn is approximately the same as the amount of twist in a comparable ring spun yarn.

Pair of delivery roller and package building mechanism:

There is a pair of delivery rollers used to take the yarn forward

The yarn received by delivery rollers is wound on the yarn package. Once the yarn leaves the hollow spindle and delivery rollers, it passes through a traverse guide. This traverse guide distributes the yarn along with the package horizontally from one side to another side. When one layer is completed, the next layer gets started. The traverse guide is used as a connection between the hollow spindle and the bobbin where the yarn is stored.

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