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Yarn to Fabric Manufacturing

A case study on spun yarn production to fabrics and finishing processes in a real-time production environment

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WEAVING

INTRODUCTION

Weaving is the production of fabric by interlacing two sets of yarns so that they cross each other, normally at right angles, usually accomplished with a hand- or power-operated loom.

In weaving, lengthwise yarns are called warp; crosswise yarns are called weft, or filling. Most woven fabrics are made with their outer edges finished in a manner that avoids raveling; these are called selvages. They run lengthwise, parallel to the warp yarns. The three basic weaves are plain, twill, and satin. Fancy weaves—such as pile, Jacquard, dobby, and leno—require more complicated looms or special loom attachments for their construction.

In OCM Weaving consisted of three major sections in total

  • Preparatory section
  • Loom shed
  • Greasy perch inspection

PROCESS SEQUENCE

WARPING

  • The weaving process starts with warping.
  • In this section, the warp ends are wrapped around the beam which is then put onto the machine.
  • A warping plan is provided to the weaving department with a master card in which all the instructions regarding the weaving process are given.
  • The wrapper makes seating according to this plan on the warping machine and by doing the required calculations.
  • While doing setting he considers the parameter of the reed width, warp length and according to that sectional width is decided.

CREELING

  • It is a process of mounting a large number of wound packages onto a unit known as a creel. In OCM truck creels are used. In this type of creel, the yarn packages are placed on spindles of truck in a preparation area.
  • At the time of a run, the yarn of each end is broken between the package and the guide and the trucks are wheeled out from the center of the creel to be replaced by the preloaded trucks.
  • It is then necessary to tie the yarn from each new package to its corresponding end in the creel.
  • Each thread is then drawn forward to the front of the creel in a strictly controlled order, which ensures that there is no crossing of the threads.
  • At the front of each horizontal row of packages, on one side of the creel, there is a row of guides where each thread passes under a tripwire.
  • If a thread breaks during the course of processing, this wire falls to make electrical contact and stop the machine before the broken thread becomes lost under subsequent ends of the yarn on the beam.
  • A-light at the end of the relevant guide bar is illuminated in order to direct the operative to the source of the broken thread.

SECTIONAL WARPING

The sectional warping machine is used for the preparation of multicolored warps to be woven as striped or checked design fabrics. It is also used for doubled grey or mono-colored warps that do not require sizing. Unlike the beam or direct warping where a warper’s beam is produced that is sent to the subsequent sizing processes, in the case of sectional warping, the weaver’s beam is produced and hence does not require sizing. In the case of single yarns that are multicolored, the yarns are sized and then wound on the sectional warp beam.

PROCEDURE

  • This is a two-stage process. In the first stage yarn end from the creel is taken to the mill via a condensing roller where they coverage into a single sheet, leasing rods for locating the broken ends, adjustable reed to set the width of a warp sheet to the exact distance between the flanges of the beam.
  • The sheet of the yarn is placed on a horizontal beam in sections. Each section contains a fraction of the number of ends required in the final sheet.
  • The length of yarn wound per section is sufficient for one weaver’s beam only. Each section is inclined to the vertical with the first section resting on an incline at the end of the mill.
  • When all the sections have been wound on the drum the second stage of the process can take place.
  • This involves the sheet being pulled off the drum and onto a beam during which time the mill transverses in the opposite direction and at the same rate as that moved in the first stage.
  • It is the transfer of warp sheet from drum to weaver beam. It requires about half an hour while beaming two pressure rollers, which are spring-loaded remain in contact with the beam to form a compact beam.
  • The beam speed is kept between 100 to 150 rpm.

 

Fig.1.17- Diagram of warping mechanism

 

DRAWING

  • In weaving the process of threading warp ends through the eyes of the healds and the dents of the reed.
  • The warp yarn required passing through the heald eyes in order to form the shed; it is not possible that the loom may be stopped to draw the ends.

DRAFTING

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  • The design is constructed on point paper by using the cross (×) and blank. The cross means that the end is passing over the pick. The blank means the end is passing below the pick.
  • Drafting determines the allocation of ends to healds i.e. which end will be controlled by which heald.
Figure 3.2: Drafting process

 

DENTING

In the woven fabric manufacturing industry, denting means drawing the warp yarn through the dent as required by the reed plan. Denting determines more perfectly the width of the woven fabric and the ends per inch (EPI).

Figure 3.3: Denting process

 

PINNING

It is done to avoid warp defects. Pinning is done separately. Each warp yarn is passed through one pin individually. If any of the warp yarn breaks during the weaving process, the pin will touch the sensor of the serrated bar, then the machine will stop working automatically.

Figure 3.4: Pinning process

 

KNOTTING

After the pinning process, when the yarns are passed through the pins to the other side, they remain open due to which they become loose and can come in the backward direction. In order to avoid this knotting of yarns take place.

TYING – IN

In the case of bulk production and the new quality having the same denting and drafting as the previous one to save the time for production, the operation of tying-in is done. If every end is tied to its corresponding end on the old beam, the drawing-in process can be omitted. The tying operation is done with the portable tying machine.

For every warping machine, there is a separate calculation device for doing settings in the machine.

  • Total number of ends = reed count x reed width x ends per inch
  • Feed ratio = according to gears (set according to the length of roll required)
  • After feeding these values, the computer will give the cone height.
  • After feeding the yarn length, the computer will give a number of rounds that we need for that length.
  • To find the total number of sections that will be on the beam
  • The number of sections = total number of ends/ creel.
  • Section width = reed width/ number of section.
  • To check the section width, there is a V reed.
  • After warping is over, beams are taken for drafting. According to the plan, ends are passed through different heald shafts and then the denting is done accordingly.

WEAVING

After denting, the beams with warp ends are taken for weaving whereby movement of heald shafts; the fabric is formed by the interlacement of yarns according to the lifting plan cut on the dobby cards.

WORKING PRINCIPLE

The main working principle of these machines is that their every process of shedding, picking, beat-up is set according to the degree of rotation to the main shaft. If not done then there are much more chances of damages to loom and fabric.

PROCEDURE

  • In the loom, the weaver’s beam is placed at the back. Yarn ends from this beam are passed simultaneously through drop wires through the heald eye of the heald frame, dents of the reed to the fall of the cloth.
  • The number of heald frames depends upon the weave and the passage of each warp thread through the heald eye depends upon the drafting plan.
  • These heald frames move up and down to form a shed through which a weft yarn is passed across.
  • Weft insertion is done through different mechanisms like a rapier, projectile, shuttle, etc. the required length of the yarn is wounded onto a weft accumulator.
  • The inserted weft yarn is cut from the entry side and pushed to the fell of the cloth by the reed. Then the tucking device in the next shade tucks in both sides.
  • All the weft yarns are inserted through the same side of the m/c.
  • The temples at the fell hold the woven cloth to prevent any weft-wise contraction.
  • The woven cloth is held tight by the tensioner rollers and is wound onto the cloth roll.
Fig.1.20- Loom warp passage

 

POST WEAVING: GREASY PERCH INSPECTION

  • After weaving each cloth goes for greasy perch inspection. In this department, various defects are inspected occurring due to faults in machines or improper work practices.
  • The defect report is continuously delivered to the weaving department technologist so that immediate action could be taken so as to correct the defects occurring in the grey cloth.
  • Greasy stain removal is done during the inspection, by spraying a solvent (e.g. carbon tetrachloride on stain spots).
  • After greasy perch inspection, the fabric is forwarded to mending, where they are seen for these defects.
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