Tuesday, July 2, 2019

WARPING PROCESS, DIRECT WARPING PROCESS AND PRECAUTIONS

WARPING PROCESS:

In composite textile mills, warping is considered the second process in fabric manufacturing. In those mills which contain fabric manufacturing only, warping is considered as the first process of warp preparation. During the warping process, a continuous sheet of many warp ends (individual warp yarn is called end) is prepared and is wound on the warper’s beam or weaver beam. The beam is a roller having flanges at both sides of it. In the warp sheet, all the ends are parallel and equally spaced to one another. Cones, cheeses or spools are used as supply package in the warping process. The no. of ends in the warp beam and flange to flange distance (beam width) are decided according to the fabric to be manufactured. The packages are mounted on the creel. In indirect warping, each end passes through yarn guide, tensioner, guide separator, drop wire, separator rods, lease reed, v – shape reed or flat reed and over the guide rollers. The warp ends are finally wound on the drum. After completing the warping, the warp is transferred to the weaver’s beam. In direct warping, yarn coming from drop wire passes through the expendable reed (zig – zeg reed or flat reed having the arrangement to reduce or increase its width). Now the yarn passes over a guide roller. Sometimes it passes through drop wire again to prevent failure of stop during warping. Finally, the yarn is wound on the warper’s beam. Since the quality of warping directly influences the efficiency of the loom and the quality of fabric to be manufactured so that it is necessary to maintain the quality of warping.

OBJECTIBES OF WARPING PROCESS:

The main objectives of the warping process are given below:

To prepare a continuous sheet of warp ends. 

To keep the all ends parallel to one another.

To improve the quality of warp yarn by modifying big knots, thick and thin places etc.

To prepare the warper’s beam or weaver’s beam for the next process.

TYPES OF WARPING:

The warping process may be categorised as follows:

Direct warping or beam warping

Indirect warping or sectional warping

DIRECT WARPING OR BEAM WARPING:

In this method of warping, single colour (mono colour) in warping is used generally. It is mainly used to prepare the warp of single-ply yarn. Multi plies warp can also be used in this warping.  The multi-coloured warp of simple patterns can also be made by this warping method. First of all, the warp is wound on the many warper’s beams. The warp yarn from these beams is transferred to the weaver’s beam during sizing.

STRUCTURE AND WORKING PRINCIPLE OF DIRECT OR BEAM WARPING MACHINE:

The common component of direct or beam warping and their working are given below:

CREEL:  

The yarn packages are mounted on the creel. It is a very important part of the warping machine. Creel is a frame of round or square section pipes and iron channels. The cone holders are arranged in vertical columns on both sides of the creel 50 columns of cone holders in each side of creel are there in the creel of direct warping machine. The number of rows of cone holders varies according to the capacity of the creel. The number of rows in the creel may range from 4 – 8 according to requirement. The yarn packages are mounted on the cone holders. A yarn guide and a tensioner are provided in the creel for each warp end. The yarn coming from the package first of all passes through the ceramic yarn guide then it passes through the yarn tensioner. The main function of the tensioner is to impart a sufficient amount of tension to the yarn. Normally inverted cups and deadweight washers type of tensioners are used in the warping machine. The number of washers and their weight depends on the yarn count used in the warping process. As the yarn count becomes finer from coarser, the number of washers is reduced its weight is also reduced if necessary.  Now the warp end passes through many ceramic guides which are arranged at equal distance to each other. The distance depends upon the length of the creel. The main objective of these guides is to keep separate each end and to prevent an end to end entanglement during warping. The second objective of this guide is to provide enough support to each end. The yarn sagging problem creates insufficient support to the yarn during warping because a long yarn try to sag is due to its own weight. Thus enough support needs throughout the passage of the warp end. Now the next passage of warp end is drop wire. Its objective is to stop the machine immediately when end breakage occurs. The creel is equipped with fully automatic warp stop motion. The indication lamps on each row are provided in the creel whenever ends breakage occurs the indication lamp puts on immediately and the machine is stopped. These indication lamps help the operator to identify the correct situation broken end in the creel.







REED AND ADJUSTING ATTACHMENT: 

The reed is mounted over the headstock of the machine. The top side of the dents of warping reed is opened. A centre mark is made in the centre of the reed. The warp ends are inserted into the dents in a definite sequence quickly without using any drawing hook. The reed using in the direct warping machine has the ability to change its width within the limit. An attachment is provided in the machine which helps to reduce or increase the reed width. This system also helps to move the complete reed. A threaded shaft across the width of the machine is used in this system, the clockwise threads are used at one end and anti-clock threads are used at another end of the threaded shaft. The threaded brackets of the same types of thread are fitted on both sides of this shaft. The ends of reeds are mounted on these brackets. A handwheel is fastened at the one end of the shaft. Whenever the operator needs to adjust the reed width, he rotates the wheel in the required direction. The threaded brackets mounted on the threaded shaft come close or go away to each other, thus the reed width is adjusted. This system further moves in the left or right direction with the help of a hand wheel and a threaded shaft, thus the operator brings the centre of the reed in the centre of the machine.

WARP STOP MOTION:  

This is an extra warp stop motion that is mounted over the headstock of the machine just after the reed. The drop pins are inserted into the electrode. Every end passes through one drop pin. When an end breaks, it falls down on the electrode and the electrical circuit is completed. The machine stops immediately. This stop motion is more effective whenever a broken end is entangled with another end and starts to move with that. In this case, the stop motion situated in the creel does not stop the machine, but this extra stop motion does not fail and stops the machine immediately in this case.

WARPING DRUM:  

The function of the warping drum is to revolve the warper’s beam. The drum rotates the beam by surface contact. The drum rotates on the bearings. The beam mounted on the hydraulic arms is free to move in any direction because it is loose on its shaft. The surface of the beam touches the surface of the drum. When the drum rotates, it also revolves the beam in opposite direction due to frictional contact. The yarn passes between the surfaces of the drum, beam and is finally tied on the beam barrel. When the beam rotates, it pulls the yarn and wound onto it.

WARPER’S BEAM:  




The warper’s beam is a cylinder having flanges at both sides. The cylinder or beam barrel is made of good quality wood. An iron shaft is inserted inside it.  Aluminium flanges are fitted at both ends of the cylinder. The iron shaft is projected outside of the flanges from 6 – 8 inches. The flange to flange distance is always fixed as per the length of the warping drum. 

BEAM LOADING SYSTEM:  

The beam lifting arms are mounted on the shaft which is fitted at bottom of the machine in front of the drum. These arms are moved in upward and downward direction on the bushes fitted in them. The top end of each arm is connected to the piston of a hydraulic cylinder. These hydraulic cylinders help move the arm up and down and help maintain pressure between drum and beam during operation. The warper’s beam is mounted on these arms. Before mounting the beam on the arms, a self-aligned bearing at each side of the beam shaft is fitted. Now beam is mounted in the brackets of beam lifting arms and it is tightened with a bracket cover. Now the beam is moved toward the drum and touches the surface of the drum.

HYDRAULIC PRESSURE SYSTEM:  

A hydraulic pressure device is used to generate pressure to bring up and down the beam, pressure also helps to prevent the slippage between drum and beam during running. Hydraulic pressure controls the compactness of the beam. Hydraulic pressure breaks the momentum of the rotating drum in case of machine stoppages. Generally, a cuboid shape oil tank is used which is located at one side of the machine. 68 no. hydraulic oil is filled in this tank. A geared oil pump is mounted on this oil tank. The inlet of the oil pump rests in the oil. The oil enters the oil pump through an oil filter which does filter the oil. The pump’s shaft is connected to the electric motor. This motor rotates the oil pump. The outlet of the oil pump is connected to the hydraulic cylinders through oil pipes at one end and through another pipe at the other end. During machine operation, a certain amount of pressure is always maintained in the system. A three positions switch is used to select the position of arms. The centre position keeps the arms in the rest position. The left side position provides downward movement and the right side position provides upward movement to the arms. Magnetic valves are used to start and stop the supply of oil into the cylinder at both ends. The pistons of cylinders come out or go inside the cylinder again as per the position of the selection switch. The piston of the cylinder operates the arms in an up and down direction. Lifting and lowering of beam take place in this way. A pressure regulator is used to reduce or increase the pressure during warping operations. 

FULL WARP LENGTH STOP MOTION:  

In today’s machines, electronic full warp length stop motion is used. The required warp length is entered in the digital counter meter. A metallic pin is fitted near the circumference of the drum on one side. A proximity sensor is mounted just opposite this pin. When the drum rotates, the proximity sensor senses every rotation of the drum. The signals are sent to the counter meter. The drums circumference or diameter is fed in the meter. The counter meter counts the rotations of the drum and converts them into metres. When warp length reaches completion, the counter meter sends a signal to the control unit and the control unit stops the machine immediately.

A.C. INVERTER DRIVE:  

An inverter drive changes the speed of the warping drum without replacing the motor pulley. A pot is provided in the machine which selects the machine speed. The machine speed appears in the display of the counter meter.

GENERAL WORKING SEQUENCE OF BEAM WARPING MACHINE:

The general working sequence of beam warping machine is described below:
The yarn is received in the form of cone or cheese from spinning mills or yarn stores. The yarn packages are mounted on the cone holders. The number of packages depends upon the total no. of ends required in the weaver’s beam and no. of warper’s beam to be made.  Now each end is drawn through a yarn guide and tensioner. Next, each end passes through many yarn separating guides. The ends are finally passed through the eyes of drop wires. Now operator draws these ends through dents of reed in a definite order. The operator loads the empty warper’s beam on the machine. The ends are passed between the drum and beam barrel surface. Three to four wraps of the ends are wound on the beam by inching the machine. The operator applies manual pressure on the end during inching to prevent slippage. Required warp length is fed into the counter meter. Now warping machine is ready to operate. An operator can run the machine by pressing the push button.

PRECAUTIONS OF DIRECT OR BEAM WARPING PROCESS:

Following precautions should be taken during the process of direct or beam warping.

The tension on the every warp end should be proper.

The cleaning of the tensioner should be done at each creel change.

The number of yarn separation guides should be according to the length of the creel. 

The warp end located at the rear side of the creel slackens due own weight. These ends are located at the rear side of the creel wind on both sides of the beam. During sizing these ends get loosed and create the problem of bowing in the fabric. Thus the tension of the ends is maintained according to location. The rear ends require maximum possible warp tension. The middle ends require less warp tension than the rear ends. The front ends require minimum possible warp tension. 

The tension should be selected in such a way that there is no false warp stop due to ends slackening.

The number of tension washers and their weight should always be adjusted after a change in warp count.

The drop wire should work properly.

The electrode of warp stop motion should be cleaned by any cleaning liquid to avoid failure of warp stop motion.

The warp ends should be drawn in creel in the correct sequence to avoid end breakage.

The reed width should be adjusted properly, improper adjustment causes loose ends at each side of the beam.

There should be no short end in the beam.

Short end in the warper’s beam cause lappers and creates end breakage during sizing process.

The warping pressure should be selected properly. If pressure is too high, it may cause yarn rupture. If pressure is too low, it may cause warp slippage on the beam.

The short ends should be mend during the process correctly.

Machine brake should work precisely and effectively. 

The oil level in the hydraulic system should be maintained regularly.

The edges of beam flanges should not be sharp and rough. 

Skip denting order should not be used if possible. There should be changed the reed.

The pitch of the creel should be selected precisely to avoid touching the surface of yarn packages to each other. 

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