Yarn clearer

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  • 1.1 Introduction

    This project work covers the different technical and theoretical aspects, related literature

    reviews, experimental findings and their both tabular and graphical representations,

    technical explanations and result analysis from our work termed Impact of different

    clearing limits of yarn clearer on yarn quality and productivity. For all known spinning

    methods of today it is necessary to have a yarn monitoring system in the last production

    process of the spinning mill, which stops the production position if disturbing faults

    occur. The machine must automatically remove the faults and replace it by a splice. The

    spinning process is not a perfect process and can produce imperfections. Another source

    for irregularities in ring spinning is the availability of flies in the air which are frequently

    spun into the yarn and accumulations of fibre fragments and dust at yarn guiding

    elements. In ringframe, all fibre and yarn guiding elements, ring traveler, pressure rollers,

    belts and spindles can contribute to yarn faults, particularly if there are defective.

    Therefore, one important rule of modern quality management cannot be implemented

    completely: Preventive actions rather than corrections afterwards!

    With the help of yarn clearer such as Uster Quantum 2, Loepfe Zenith etc. we can remove

    different types of prominent yarn faults thus improving quality of yarn.

    1.2 Objectives

    To study about different yarn clearing systems and clearing limits from literature.

    To analyze various types of yarn faults.

    To process ring yarn of same specifications under three different clearing limits in

    Uster Quantum 2 and observe the resultant cut data.

    To analyze yarn quality and characteristics before and after winding.

    To study the effects of the three different yarn clearer settings on productivity and

    wastage generation in winding machine.

    .

    Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 2

  • Chapter 2

    Literature Review

    Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 3

  • 2.1 Yarn clearer

    The device which is used to remove faults (thick places, thin places, foreign matter) from

    the yarn is known as yarn clearer. Yarn clearing improves the quality of the spun yarn and

    hence of the cloth made of it.

    Yarn clearing is usually part of the yarn winding process. The yarn from a number of

    spinning bobbins, called 'cops', is wound on to larger packages called 'cones' for

    subsequent processing into fabric. During the winding the yarn was traditionally passed

    through the narrow slit in a steel plate of a yarn clearer or slub-catcher. The object was to

    catch thick places, or slubs, which occurred when the spinning process suffered an

    aberration, and to prevent them being woven into the fabric to present unsightly faults.

    In modern textile industry, after detecting the faults, the clearer cuts the faulty pieces

    from the yarn, and after that the piecing device joins the cut ends. [1]

    2.2 Types of yarn clearer

    There are two types of yarn clearer

    1. Mechanical type

    Conventional blunt type

    Serrated blade type2. Electronic type

    Capacitance type

    Optical type

    2.2.1 Mechanical type

    A mechanical clearer maybe as simple as two parallel blades. The distance between the

    blades is adjustable to allow only a predetermined yarn diameter to pass through. A

    thicker spot on the yarn (slub) will cause the tension on the yarn to build up and

    eventually break the yarn. Consequently, this type of device can only detect thick places

    in the yarn. [2]

    2.2.2 Electronic type

    Electronic yarn clearers ensure excellent clearing to be obtained with minimum

    mechanical stress on the yarn. In order to be able to monitor and to evaluate thick and

    thin places as well as deviations from the desired yarn count, the thickness of the yarn

    must be converted into a proportional electrical voltage. The course of voltage is called

    Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 4

  • yarn signal. This conversation is carried out either with the sensor of the capacitive

    measuring principle or with the sensor of the optical measuring principle.

    The capacitive measuring principle

    The electrical measuring condenser (1) forms the sensor for the capacitive monitoring of

    the yarn mass. This is done by two parallel metal plates, the electrodes. In the space in

    between (2), the two electrodes build an electrical field when putting on an electrical

    alternating voltage (3).

    Figure 2.1 Capacitive sensor

    If a yarn (4) is brought into this field, the capacitance of the measuring condenser is

    changed. From this change, an electrical signal, the yarn signal is (5) is derived. The

    change in the capacitance depends, besides of the mass of the yarn and of the dielectric

    constant of the fibre material is used, on the moisture content of the yarn.

    With the capacitive measuring principle, the yarn signal corresponds to the yarn cross-

    section and yarn mass respectively, which is located in the measuring field. Changes of

    the yarn mass cause a proportional change of the yarn signal.

    The optical measuring principle

    The infrared light source (1) and the photocell (3) represent the sensor for the optical

    monitoring of the yarn thickness. The infrared is light is scattered by a diffuser (2) in the

    light field and reaches the photocell (3). The photocell emits a signal, which is

    proportional to the amount of light.

    Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 5

  • Figure 2.2 Optical sensor

    If a yarn (4) is brought in the light field, parts of the light will be absorbed by the yarn.

    The amount of light, which hits the photocell, is smaller. From this change, an electrical

    signal, the yarn signal (5) is derived.

    With the optical measuring principle the yarn signal corresponds to the diameter of the

    usually round yarn, which is located inside the measuring field. Changes of the yarn

    diameter cause a proportional change of the yarn signal. [3]

    Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 6

  • Table 2.1 Comparison between capacitive and optical principle

    Property Capacitive principle Optical principle

    Yarn signal Corresponds to the Corresponds to the diameter

    mass/cross section of the of the yarn and the visual

    yarn or the number of fibres impression.

    in the measuring field.

    Effective measuring field The current yarn signal is The current yarn signal is

    length: different measuring the mean value of the piece the mean value of the piece

    field lengths influence the of yarn which is located in of yarn which is located in

    monitoring of very short the measuring field. the measuring field. Length:

    yarn faults. Length: 7 mm 3 mm

    Evaluation of the yarn fault

    Normal yarn fault The fault is evaluated with The fault is evaluated with

    the full increase of the the full increase of the

    cross-section in percent. diameter in percent.

    Voluminous, visually large As the number of additional The very voluminous yarn

    appearing yarn fault fibres is not extremely high, fault absorbs a lot of light.

    this yarn fault is considered Therefore, the fault is

    as relatively insignificant. considered as significant.

    Short yarn faults, length: 3 The increase of the diameter The fault is evaluated with mm

    of this short fault is the full increase of the

    averaged over the whole diameter.

    measuring field length. The

    fault is only evaluated as

    half of the size.

    Very compact yarn fault The fault is evaluated with Compact yarn fault absorbs

    the full increase of the small amount of light.

    cross-section. Due to the Increase of the diameter is

    The distance between two higher number of fibres considered as insignificant.

    white lines is 1 cm. thick place absorb more

    dye.

    Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 7

  • 2.3 Comparison between mechanical and electronic type

    Electronic clearer are more sensitive than mechanical clearers.

    In case of mechanical clearers there is abrasion between yarn and clearer parts

    but in case of electronic clearers there is no such abrasion.

    Mechanical clearers do not prevent soft slub from escaping through clearer

    where as electronic type does not allow passing of any types of faults.

    Mechanical type does not break the thin places and the length of the fault is not

    considered.

    Mechanical clearer are simple and easy to maintain while the electronic clearers

    are costly and requires high standard of maintenance. [4]

    2.4 Development of yarn clearer

    In 1960 Zellweger Uster launched the first electronic yarn clearer, the USTER

    SPECTOMATIC. With one single, central setting it could be determined, from