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Monday, March 16, 2015

Main Check points in Weaving

Constant vigilance of men, machines, materials and atmospheric conditions is required for smooth and efficient working of a loom shed. Though the checkpoints are already known to the supervisors, it is vital that they should be conscious of these aspects while patrolling the department.

Loom

The followings are details of the check list:
  • Conduct a quick round in the loom shed at the start of the shift along with the outgoing supervisor to find out: Back-log of production targets from the previous shift, labor adjustment etc.
  • Instruct the humidity attended on necessary adjustments. See that a regular record of temperature and relative humidity in the shed is maintained.
  • Monitor the availability of drawn beams to minimize the number of looms being kept idle for want of weaver’s beam.
  • Check the availability of weft yarn in the weft storage room.
  • Check, at suitable intervals, the weft doffs in the storage room for build characteristics and yarn-content of pirns.
  • Conduct a loom-to-loom detailed round to check quality of production.
  • Visit the folding department and collect information from cut-lookers. Point out the major defects to weavers and jobbers and set up a network for follow up action. Caution the weavers and jobbers who produce a large number of fabric defects.
  • Inspect the mechanical condition of loom at beam fall.
  • Inspect the looms producing major smashes and investigate the probable causes for the same. Ensure that the operators mend these smashes properly.
  • Adopt a sequence of operations while applying new shuttles on looms. Apply a new shuttle on a newly beam-gaited loom only and in the day shift preferably.
  • Inspect the looms at the start of new beams, for: pick density, with the help of a pick glass, reed space, with a tape, fabric cover etc.
  • Monitor the jobber’s method of gaiting new beams. Ensure that short-term checks are carried out by the jobbers on: shed opening, picker condition, shuttle in shuttle boxes etc.
  • Check the warp-stop motions on looms for their functioning by observing movement of various parts and by pressing down intentionally a drop pin or two to see whether the loom stops.
  • Refer to production records for loom wise and weaver wise production and efficiency figures. Instruct the weavers who are consistently responsible for low production.
  • Refer to the SQC reports for the overall performance of the loom shed in terms of average warp and weft breaks and frequency of other stoppages.
  • Refer to the hard waste records for the normal level of hard waste in the loom shed. Particularly, check the sweeping waste.
  • Inspect regularly the stores items for quality and consumption. The consumption figures can be obtained from the stores records.
  • Observe practices of weavers while patrolling the department. Overlooking floats, not keeping the spare shuttle ready, not taking a round in the beam alley, not reporting the machine faults to the jobber, staining the fabric or weft bobbins with oily hands, not mending broken ends in time-specially on ordinary looms, etc. are some of the commonly observed faulty weaver practices. Give proper instructions and warnings, if necessary, to defaulting weavers.
  • Observe general cleanliness and housekeeping practices in the loom shed. Ensure that proper cleaning frequencies are followed.
  • Inspect the materials handling system and equipment used for transporting weaver’s beams, weft pirns and fabric. Ensure timely maintenance of such equipment.

Quality control activities in loom shed

The quality control function is required to monitor the qualitative performance of the incoming material, in-process material and the finished product. This involves conducting of studies/tests, both routine and special.

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Automatic loom

Routine Studies
End breaks and operations
Warp and weft breakage studies should be conducted once a month for each count. The breaks should be noted case wise. In the case of ordinary looms, additional information regarding weft changes should be noted. From the data collected, warp and weft breakage rates, as also the weaver operations can be calculated for each count.

Efficiency
Loom-shed efficiency should be studied every day by conducting a snap round the department. If the number of looms in the shed is more than 1000, the round may have to be split in two parts to cover all the looms.

Fabric defects
A snap round should be taken every day in the department for observing fabric defects. The number of rounds should be increased to 2-3 per day when the defects are excessive. While observing the loom for the incidence of fabric defects, the type of defect should be noted on an observation sheet. This will provide information on the commonly occurring types of defects and will also help to create quality consciousness among the weavers.

Speed checking
Loom speeds should be checked at least once a month. The procedure to be followed is to rest a finger on the picking shaft of a loom and count the strokes for two minutes. A maximum loss of 2 rpm from the rated speed should be allowed.

Transfer failures
Two percent of the total automatic looms must be studied every month of transfer failures, for one hour each. This study can be combined with the breakage study. The incidence of the transfer failures and lashing-in would indicate the performance of transfer mechanism.

Hard waste
The hard waste level is to be calculated every month from records. This will show the general trend. It is suggested to keep a watch on the level of sweeping waste as weavers are often found to throw waste indiscriminately on to the floor.

Colored weft shade
A round should be conducted once a day to cover all looms and the pirns kept on the looms should be observed for shade variations. The weavers should be asked to segregate the light and dark pirns.

Ordinary looms working with one shuttle
A snap round should be taken once a week or fortnight in the entire shed and looms working with only one shuttle, unworkable spare shuttle and spare shuttle under repair should be noted and the number expressed as a percentage of total looms observed.

Functioning of Warp stop motion
Every loom having a warp stop motion should be checked for its functioning once a fortnight or month. A snap round taken in the loom shed once a week or fortnight will help to observe the functioning of the mechanisms of automatic looms. This study can be combined with the snap study for fabric defects.

Survey of ejected pirns on automatic loom
The ejected pirns at the looms should be observed during the transfer failure study for the presence of excessively long length of yarn or absence of bunch.

Sortwise efficiency
Sortwise efficiency should be calculated every month from records.

Maintenance audit
When the Statistical quality control department is assigned the work of maintenance audit, counterchecks should be planned in accordance with the maintenance schedule.

Life estimation of stores items
Sample trials are very essential to estimate life or quality level of an incoming lot. The sample size should not be too small as there can be very high sampling errors. It should also not be very large as it will demand considerable time and effort. Normally, a sample size of about 24 may be preferred for the trials. Even so, it is not necessary to wait till all the items are consumed, but a fair idea can be formed from a truncated sample when 50-79% of the items are consumed.

Productivity
Productivity calculations should be carried out once a month.

Stores consumption
Stores consumption should be found out from records. This will indicate the looms consuming more than standard level of items.

Labor employment
The average labor employment should be calculated once a month. This will help in avoiding the use of more than necessary labor force in the shed.

Fabric inspection
About 2000 m each of grey and finished fabrics covering all the major sorts should be inspected every month on the inspection table for quality and incidence of fabric defects. The data so collected should be analyzed weaver wise and loom wise.

Packing and baling inspection
The entire operation of packing and baling should be counter—checked whenever required with respect to assortment, number of pieces, quality of work, slips, packing material etc.

Cut-looked production
At least one piece from the cut-looked production should be checked twice a week, per cut-looker.

Humidity
A careful monitoring should be exercised and periodical readings taken on the hygrometers placed in different sections of the shed to maintain uniform relative humidity in the weaving shed all through the shift. Readings of the hygrometer kept outside and inside the shed should be taken at the same time. These observations may be carefully studied and used as guidance for controlling general humidity in the shed.

Reconciliation between yarn and fabric
As a part of the management control, the SQC department should match the consumption of yarn and production of fabric through monthly reconciliation statements. Such a procedure helps to provide a continuous vigil on the entire production cycle and helps to assess the actual material losses in the form of process waste, invisible waste and so on. A reliable method for reconciliation has been developed by BTRA36.

Special studies
Hard waste
Whenever required, detailed cause wise hard waste studies should be conducted to pin-point the areas responsible for excessive hard waste.

Yarn content on weft pirn
In the event of any problem regarding weft supply, yarn content of pirns should be checked either by measuring length of yarn on a few pirns individually or by checking the pirn doff weights. In the case of direct weft, count and yarn properties may also be checked.

Sunday, January 11, 2015

Different parts of a Loom

Weaving is done on a machine called a loom. All the weaves that are known today have been made for thousands of years. The precise shape of the loom and its mechanics may vary, but the basic function is the same. Warp yarns are held taut within the loom, and weft yarns are inserted and pushed into place to make the fabric.

loom parts

Major parts of a loom

Warp beam: The warp beam, which holds the lengthwise yarns, is located at the back of the machine and is controlled so that it releases yarns to the weaving area of the loom as needed.
Whip roll: This is guide roller which directs the warp threads on their way to the lease rods and heddles.
Lease rods: Another guiding device it is for the warp yarns. These are two sorts of wooden or glass rods set between the whip rolls and the heddles.
Alternating warp threads can be kept separate by passing over and under these rods.
Heddles/Healds: A heddle is a wire with a hole or eye in its center through which a warp yarn is threaded. There are as many heddles as there are warp yarns in the cloth, and the heddles are held in two or more harness.
Harness: A harness is a frame to hold the heddles. The harness position, the number of harness, and the warp yarns that are controlled by each harness determine the weave pattern or interlacing.
Bobbin and Shuttle: The filling thread is wound on a bobbin which sets into a shuttle or bobbin container. As the shuttle passes back and forth through the warp shed, it releases thread from the bobbin and so forms the filling cloth.
Reed: This is inevitably a combination made up of steel wire rods set vertically in a frame. The spaces between the wires are known as splits or dents and are kept even and parallel. This is the first function of reed.
Its second function is to feed the filling thread into position. To do this it has to move in a back and forth motion.
Breast beam: The bar his is, at the front of the loom over which the cloth passes on its way to the cloth roller.
Temples: They divide at the edges of the cloth which supports to maintain fixed dimension in width.
Cloth roller: It is located at the front of the loom, hold the completed fabric.

Tuesday, December 2, 2014

Water Jet Loom

About Water Jet Loom –

An effort to achieve – ­­­
-         Higher meters per loom per hour
-         Faultless fabric
-         Reduction in weight of weft carrier
-         Reduction in cost of weaving
-         Reduction in noise level to 90 Dba
     Weaving machine makers produced gripper shuttle and rapier machines belonging to second generation of shuttle loom. But in both machines, something solid enters shed and yarn is suddenly accelerated to very high velocity-stretching tender yarns undesirably.
     Then third generation of Air Jet and Water Jet looms when fibre spun as well as hydrophobic filament weft was carried on a hydraulic soft cushion.
The other methods for higher production were –
-         Adoption of multi-width weaving.
-         Making weaving process non-intermittent such as in multi-phase weaving machines.
-         Reduction in down time i.e. continuity in warp supply without stoppage for package change.

Specialties of Water Jet loom –

-         Water is ejected under pressure from nozzles at picking side and pushes pick through shed length.
-         Yarns coated with protecting water repellent sizes cannot be woven successfully as no size covers whole yarn length completely.
-         Feel of sarees and dress materials is simply super - because ‘O’ twist textured yarns elasticity is preserved in toto.
-         Zero twist textured polyester or nylon needs to be sized – preferably on end to end sizing machines with PVA base sizes.
-         Used water is purified and re-circulated.
-         Each loom has its own water tank and small pump.
-         A 90 in. loom hardly consumes about 1.5 liters of water per day.
-         A fixed hardness and temperature of water is a must, as viscosity fluctuation disturbs picking energy.
-         Normal looms are two nozzle type, but latest machines are four nozzle and multicolored.
-         A revolving synchronized cam compresses a spring and controls piston strokes inside a pump cylinder. Thus, picking force of jet is directly proportional to pistons stroke length.
-         Water is accelerated to required force inside the pump cylinder and the emerging jet force can thus be altered as needed, for a weft count and machine width, as well as its ppm.
-         It takes a parabolic path – the force of gravity pulls it down and disintegrates.
-         Atmosphere must be free from fluff and dirt, to allow water molecules to move freely.
-         Through jet velocity diminishes as reed width increases; wet weft clings to reed and does not contract.
Resultant – filling velocity is negative due to retardation.
            Vr = Vp - Vu
            Where, Vr is resultant weft velocity.
            Vu and Vp are initial and final weft speeds.

Picking Force

            It depends upon –
-         Pump pressures.
-         Volume of water ejected stroke.
-         Nozzle shape and cross-section.
-         Friction between water and weft yarn.

Water jet loom
a.     A weaver can operate picking manually with the help of a foot pedal. In case of a pick break the electronic mechanism stops machine in open shed and the break can be easily mended.
b.     Start/stop, slow/forward and reverse is controlled by push buttons.
c.      Warp let-off mechanism is electronically controlled.
d.     Basic frame structure of an Air and a Water-jet are almost identical and a Water-jet can be converted into an Air-jet machine.
e.      Picking units are placed separately and looms parts are made of corrosion free materials.
f.       Each pick is withdrawn and measured by a constant diameter monitoring device before presenting it for picking. Thus weft unwinding tension from supply package is minimum and constant.
g.     Hairy weft, blocks nozzle hole should be avoided.
h.     Each pick uses 0.5 ml to 2.5 ml of water as per machine width.
i.        Water pressure is about 220 KN/m2.
j.       Selvedge in fringed and catch cords are thicker than body warp ends.
k.     Weft waste is about 1.75 to 2.5% depends upon the weft. Catch cords are drawn from separate pulleys and do not pass through reed. After 2 to 3 mm from selvedges, free pick ends are firmly secured by strong leno ends.
l.        There are few suction slots over breast roll for sucking-off excess water.
m.  In pure PE fabrics selvedges can be heat fused.

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An overview of weft insertion element of Air Jet

Wednesday, August 20, 2014

An Overview of weft insertion elements in air jet

Weft Storage System – Drum Feeder

Following figure shows the schematic diagram of a drum feeder for air-jet weaving machines. The weft yarn is drawn off the package and wound onto measuring bands 2 by the rotating motion of yarn guiding tube 1. The pick length depends on the fabric width. The pick length is set by adjusting the measuring bands and the number of coils. The electromagnetically controlled stopper pin 3 releases the weft yarn at the machine angle set.

Weaving element

Tuesday, August 19, 2014

Operation principle of air jet loom

Operation principle of air jet loom:
Air jet weaving machines were invented in Czechoslovakia and later refined by the Swiss, Dutch, and Japanese were designed to retain the tension less aspect of the picking action of the water jet while eliminating the problems caused by the use of water.
The yarn is pulled from the supply package at a constant speed, which is regulated by the rollers, located with the measuring disk just in front of the yarn package. The measuring disk removes a length of yarn appropriate to the width of the fabric being woven. A clamp holds the yarn in an insertion storage area, where an auxiliary air nozzle forms it into the shape of a hairpin.

Air Jet loom

Tuesday, January 28, 2014

Definition, Classification and parts of Loom

Definition of loom | Classification of loom | Different parts of loom

Loom: Loom is a machine or device which is used to produce woven fabric by interlacement of warp and weft yarn. Ginning, opening, cleaning, carding, combing, drawing, spinning, winding, warping, sizing, beaming are the process prior(পূর্ববর্তী) to weaving. All these process converge (মিলিত হওয়া) on loom.
Classification of loom:
        a)      Hand loom.
        b)      Power loom.
Hand loom:
       1.      Primitive or power loom.
       2.      Pit loom.
                                i.            Through shuttle loom.
                              ii.            Fly shuttle loom.
       3.      Frame loom:
                                i.            Through shuttle.
                              ii.            Fly shuttle.
       4.      Chittranjan loom.
       5.      Hattersley loom.
Power loom:
       1.      Conventional power loom:
                                i.            Simple.
                              ii.            Automatic. 
       2.      Modern loom:
                                i.            Jet loom.
                              ii.            Rapier loom.
                            iii.            Multiphase loom.
Jet loom:
a.       Air jet loom.
b.      Water jet loom.
                    Rapier loom:
a.       Single.
b.      Double.
                    Multiphase loom:
a.       Plain.
b.      Circular.
Different Parts of a Loom:
Loom is a machine or device which is used to produce woven fabric by interlacement of warp and weft yarn.

Different Parts of a Loom
Short Description of Loom is given below: 
Heald/Heddle: Wire or cords with eyelets that hold warp yarns in a place.

Heald shaft/Harness: A wood or metal frame that holds the headl/heddles in position in the loom during weaving. It is usually more than one.

Shuttle: This is a vehicle for weft & passes through the divided warp for the interlacement of the warp & weft.

Shuttle box: Compartment of each end of the sley of a shuttle loom used to retain the shuttle between picking motion.

Picker: It is a piece of leather or other metal placed in grooves or on a spindle inside a shuttle box.

Beams: A cylindrical body with end flanges on which a multiple of warp ends is wound in such way to permit the removal of these yarns as a warp sheet.

Front rest: It is a fixed roller placed in front of the loom above the cloth beam & act as a guide for the cloth to wind on to the cloth beam.

Lease rods: The division of warp yarn into one & one, two & two, & so on is termed as lease. The two rods passed between the two successive divisions of warp yarns are called lease rods.

Slay: It is the portion of loom that carries the reed and oscillates between the harness & the fell of the cloth.

Reed: A comb like wire or device used to separate yarns on a loom & to beat up the filling during weaving.

Treadle: The treadle is a paddle or lever under a loom with which a thread is connected by means of cords.

Temple: Roller device on a loom that hold the cloth at a proper width to prevent it from being drawn in too much by the filling.