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Sunday, January 18, 2015

Description of a Precision winder

The main feature of precision winder is the spindle in which the package is mounted and it directly gets drive. The precision winder is one, in which there is a constant ratio between the speed of the spindle which carries the package being wound and the speed of the traversing mechanism.
     This winder has the capacity for winding almost all types of yarn such as cotton, rayon, synthetic, spun rayon, linen etc. Besides, fineness and quality of the yarns do not offer any difficulty in winding on this machine. Even fine denier nylon can be wound on it without any practical difficulty. The types of wind that can be produced on this machine are close and open wind. The number of winds obtainable ranges from 40mm to 100mm.
     The passage of material through the important parts of the machine is shown in the following figure –

Precision winder

     The yarn from the supply package passes through the thread guide and on the gate type of tensioner. The tension of the running yarn is easily adjustable to suit the requirements. The machine is provided with a thread stop motion which stops it in the event of a yarn breakage or exhaustion of supply package. The yarn then passes to a traversing guide. The traverse guide consists of a steal roller plated with chromium, which is a hard metal. As such, it will prevent wear to a very great extent. The traverse bar, to which the guide is attached, makes to and fro movement through a guide provided with self oiling arrangement. The important parts of the traverse motion are fully enclosed to prevent accumulation of dust and dirt which may affect its correct functioning. The cam is fully enclosed in an oil box to keep it lubricated all the time by the splash of the oil. The setting of the dog segment permits fine adjustments. The winding pressure can also be regulated with precision according to requirements. The tapering of the cone can be regulated to the desired extent by means of an indicator device provided on the machine. The winding speed of the machine can be adjusted from 200 to 400 meters/minute to suit yarns of different qualities and counts.
   For cotton the yarn speed is 400 m/min
           For spun rayon the yarn speed is 400 m/min
For nylon the yarn speed is 350 m/min
     The spindles are located in horizontal position and get their drive from the motor. The spindle rotates at a constant speed and hence the package will increase in diameter, so the yarn tension will also increase, which in turn will increase the elasticity of the yarn. To avoid this defect the tension of the yarn is reduced and the diameter of the package is increased.
     The various arrangements described above enable the machine to wind yarns with different characteristics. Although it is specially designed for producing delicate man-made fibres like nylon, terylene etc., the machine can be employed for fine cotton yarns where the conditions are favorable for its use.

Saturday, January 17, 2015

Pirn Winding

Definition of pirn

A pirn or quill is a weft bobbin that is placed inside a shuttle in shuttle weaving. As the shuttle travels back and forth across the width of the shuttle loom, the weft yarn is unwound from the pirn through the eye (for ordinary shuttle) or slot (for automatic shuttle) of the shuttle and lay in the shed. The yarn on the quill is tapered at one end such that the yarn with drawl takes place continuously without entanglement.

Pirn winding process

Winding of a quill is different from the regular winding process. In quilling, the yarn is transferred from a larger package to the smaller quill, which is shown in figure. Also, the inspection of yarn is not part of the process, therefore, there is no yarn clearing zone.

Pirn winding

The traverse mechanism is also different because of the different geometry of the quill. The traverse here does not go back and forth along the package. It only builds yarn on one part of the package at a time, which is shown in the figure. Therefore, quill building is somewhat similar to the building of a bobbin on a ring spinning frame. This type of winding helps reduce ballooning effects, maintain uniform tension, and reduce the possibility of slough-off.
The machines that are used to wind quill are called “quillers” or pirn winding machines. These machines are automatic, which means that when the quill is filled, it is doffed and an empty pirn is placed on the spindle automatically. With the elimination of the shuttle looms, the quill winding process is also disappearing.

Thursday, January 8, 2015

Defects in Wound Packages

The main aspect of the quality of preparation in winding is the production of a fault free package that will unwind smoothly during warping. Some of these faults are caused by faulty machine settings while others are caused by incorrect work practice. Hence periodic checks on machine conditions, settings and proper supervision of operatives are necessary in order to minimize package faults. Some of the more commonly occurring package defects, their causes and remedies are given below –

Types of wound packages defects in winding

The following are the important defects that commonly occur in wound packages:
Stitches on cone
This is due to improper laying out of ends onto the cone at reversal of yarn path. It causes more end breakages in the subsequent processes and also leads to excessive yarn waste.
-         Cone holders that are improperly set and are vibrating
-         Tension brackets misaligned with winding drum
-         Wrapping of coils of thread around the bottom of cone holder
-         Traverse restrictors fixed at incorrect position
Corrective action
-         Overhauling of cone winders to be done time to time
-         Setting of cone holder and alignment of tension brackets with the drum to be done regularly

Stitches on cone

Ribboning or patterning
In this type of defect a ribbon like structure is formed on the circumference of the cone. It results in high level of slough off during unwinding, excessive yarn waste and uneven dye pick up in the case of dye packages.
-         Restriction in the rotation of the winding spindle
-         Improper setting of cone holders
-         Cam switch set improperly
-         Loading of lint in the groove of builder cam
Corrective action
-         Cone winders are to be overhauled periodically
-         Anti patterning device is to be checked regularly
-         Cone holders are to be properly lubricated so as to ensure their free movement

Ribboning or patterning

Soft package
It is caused due to abnormal softness of the structure of the package. In this case the overall density of the package is lower. It results in soft packages either at the base or at the nose of the cones.
-         The winding spindle is not properly aligned to the improper alignment of winding spindle to winding drum
-         The tension during unwinding is inadequate
-         Loading of the cradle is insufficient
Corrective measures
-         The tension during unwinding is to be kept between 6-8% of single yarn strength
-         The pressure at the cradle is to be maintained at required level

Soft package

Bell shaped cone
In this type of defect, the cones are tightly built at centre and appear in the shape of a bell. Such type of defect in the packages leads to excessive breaks during subsequent processes.
-         The tension of yarn is high during winding
-         Improper setting of cone holders with winding drum
-         Paper cones being damaged at the middle
Corrective measures
-         Cones are to be checked for quality during purchase
-         The tension during unwinding is to be kept at required level

Bell shaped cone

Nose bulging
It results in bulging of bunches of yarn at the nose of the cones. This leads to slough off during warping.
-         Setting of cone holders to winding drum is incorrect
-         Periodical inspection of settings in machines
Corrective actions
-         Avoiding use of damaged paper cones
-         Tenters to be instructed to adopt correct work practices

Nose bulging

Collapsed cone
In this type of defect, the structure of the package itself gets collapsed. This kind of defect in the packages cause excessive breaks during warping and tend to generate a high level of hard waste.
-         Use of poor or damaged cones
-         Poor system of material handling
-         Maintaining non optimum unwinding tension
Corrective actions
-         Tenters to be trained on correct work practices
-         Proper material handling devices such as cone transport trolleys to be used
-         Cone inserts to be used for paper cones

Collapsed cone

Ring shaped cone
This defect results in the formation of ring shaped bulge across the cross section of the cone. It results in more end breaks in the subsequent processes and also causes slough off during unwinding.
-         Incorrect setting of cone holder
-         Wrong placement of tensioners in the tensioning assembly
-         Traverse of yarn affected due to defects in the grooves of the drum
Corrective measures
-         Due replacement of defective drums and stop motion wires to be ensured
-         Periodic inspection of cone holder settings and tension assembly to be carried out

Ring shaped cone

Wednesday, January 7, 2015

Technical Features of a high speed drum Winding machine

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In high speed winding the yarn is wound at a very high speed. The yarn used as supply package is in the form a ring bobbin or cop and this is converted in cones or cheeses weighing about 1.5 to 2 kgs. The winding speed may be about 1400 rpm. In general the high/super speed winding machines incorporate the following features –
-         Creel for holding supply packages
-         Thread guide and balloon breaker
-         Tensioner
-         Clearer or slub catcher
-         Winding drum
-         Bobbin cradle
-         Automatic thread stop motion
-         Full bobbin stop motion
-         Ribbon breaker or anti-ribboning device
-         Driving arrangement

Supply creel
A creel or stand is fixed at the bottom of the machine in front and this accommodates ring cops which are used as supply packages. The capacity of the creel is equal to the number of winding drums in the machine. The creel carries holders in the form of pins or rods, upon which are mounted the ring cops. The supply packages are mounted such that unwinding of the yarn from them takes place from the nose portion (overhead unwinding).

Supply creel

Thread guide and balloon breaker
The yarn after being unwound from the supply package is immediately made to pass through a metallic thread guide above it. The yarn passes to the other devices of the winding machine after passing through the thread guide. Different types of thread guides are used. Some of the well known ones are the roller guide, winding accelerator etc.

Balloon breaker

One of the most important aspects of winding is the control of yarn tension. The tension device gives the required amount of tension to the yarn during winding. The tensioner serves a two-fold purpose. Firstly it enables the weak place in the yarn to be removed and secondly it helps to control the package density of the wound package and thereby ensures uniform density of the wound package. Besides, tensioners also help to remove the impurities adhering to the surface of the yarn.
There are different types of tensioners used in high/super speed winding machines and they may be classified into the following categories –
-         Washer type tensioners
-         Spinning disc or revolving type tensioners, and
-         Gate or grid bar type tensioners

Yarn guides are necessary to control the yarn path during winding or unwinding. They are generally made of ceramic or steel material and are available in various shapes depending on the unwinding requirements. The yarn may unwind sideways or over end. In the former case, the unwinding may be smooth without any undue vibration. If, however, vibrations may be present or the unwinding is not smooth, yarn guides may be required to control the path of yarn. In the latter case, the yarn does not unwind along a fixed path but rotates. This rotation or circular motion of yarn is termed as ballooning. The position of the yarn guide will influence the shape of the balloon, for a given size of package and yarn speed. It also influences the yarn tension. Hence the position of the yarn guide is an important aspect to be considered.

Clearer or slub catcher
These are also known as snick plates or yarn clearers. They are used to remove the yarn imperfections such as thick places, thin places and slubs. In case of conventional or mechanical type of clearers, thick places and slubs are removed and the tensioners remove the thin places. Thus in winding machines in which the conventional clearers are used the tensioners act partially as yarn clearers in that they remove the thin places. In case of modern clearers which are of the electronic type, the clearer removes all the three types of yarn imperfections and the tensioner only performs the function of ensuring compactness to the wound package.

Winding drum
This is the most crucial part of the winding machine, on which the wound package is built. The winding drum performs the dual function of winding the yarn on to the package (cone or cheese) and traversing it longitudinally. Thus it builds the package diametrically and longitudinally. In other words, it decides the dimensions of the full cheese or cone. The cylindrical drum consists of grooves cut helically on its circumference from one end to the other and vice versa. These grooves enable the yarn to be traversed. Thus the movement of the drum is described as ‘rotary’ traverse.

Winding drum

Cone or cheese holder
This is also known as the bobbin cradle and acts as a support for the winding package which is in the form of a cone or cheese. The package is normally wound on metal or bakelite tubes or more commonly on paper cones. The bobbin cradle is a device that supports the wound package and enables it to be rotated at high speeds during winding. This device connected to an automatic thread stop motion, which lifts the device off the winding drum in the event of thread breakage during winding. If the winding package is not lifted clear of the drum during a thread breakage, the broken end could possibly get embedded in the layers of the yarn in the package. This would make it difficult and time consuming for location of the broken end on the wound package. In the high speed winding machines, different types of arrangements are available for holding the cheeses or cones. The important types of cone/cheese holders are –
-         One arm cone holder
-         Two arm package cradle, and
-         Radial cheese holder

Automatic broken thread stops motion                                                
Since the wound packages rotate at high speeds, it is necessary that stop devices be provided to stop winding in the event of thread breakage or exhaustion of supply package during winding. The stop motion should be able to immediately lift the particular cheese or cone out of contact with the winding drum in such an event.
If the cone or cheese is allowed to run on the winding drum, after thread breakage, the end of the broken thread will be embedded and lost in the layers of yarn on the packages. This would render it difficult for the winder to locate the broken end on the cone. Also the production of the particular cone will be affected due to the delay in locating and mending the embedded broken end. Further, the yarn on the cone will be damaged due to the same layer of yarn being constantly rubbed against the winding drum at such a high speed for that period.

Full package stop motion
As soon as the wound package has reached the preset or predetermined size, the full package stop motion automatically lifts it out of contact with the winding drum or shaft. This is necessary to obtain equal length of yarn on all the cones or cheeses of the particular set or lot as otherwise it causes problems in warping due to different cones in the warping creel exhausting at different times. The warping machine production and efficiency is adversely affected in such a case. Further, in the case of cheeses which are to be dyed in that form, it is necessary to have all the cheeses of particular size according to the spacing of the spindle which holds them in the cheese dyeing machine.

Ribbon breakers
These are also variously known as pattern breakers or anti-ribbon devices. The patterning is a defect that occurs during winding. Ribbons or patterns are formed when each additional layer of yarn is laid exactly in the same position of the previous layer on cone or cheese during winding. The pattern or ribbon so formed, is however, neither visible to the naked eye nor has any adverse effect on the subsequent process for which the cone or cheese is intended. Also it will not be possible to obtain uniform dyeing or bleaching, since the flow and penetration of dye or bleach liquor will be adversely affected by the yarn where the ribbon is formed. It is therefore essential that the formation of ribbon has to be eliminated. There are three methods for doing this –
-         Method based on  changing the speed of the winding drum
-         Method based on lifting intermittently the winding package from the winding drum
-         Method based on the use of non-intersecting grooves

Driving arrangement
The winding machines are usually driven from individual motors, which transmit motion to the winding shaft through either reduction gears or three stage pulleys. Each side of the machine may have a separate motor, so that one may run independently of the other. Push button control may be provided at one of the ends of the machine to start or stop. The individual motors are usually three phase motors provided with automatic arrangement for breaking the circuit at regular intervals in order to alter the periodicity. A three stage pulley enables speed variations to be made according to the type of material worked without the necessity of altering any gearing.

Friday, January 17, 2014

Definition, objects and requirements of Winding

Definition of winding | Objects of winding | Requirements of winding | Types of Winding

Winding is one of the most important operation, which is mainly occurred in spinning section. Besides, it is also important in fabric manufacturing. In fabric manufacturing, directly winding is not so much important, but rewinding is so important. The creation of large yarn packages that can be easily unwound, is called winding. This makes using the yarn on subsequent machines both easier and more economical.
So we can say that, the process of transferring yarns from ring, bobbin, hank into a suitable package is called winding. It may be electrical or mechanical.
For warp winding → Cone, cheese, flanged bobbin.
For weft winding → Pirn, cop.
Winding is one of the most important operation, which is mainly occurred in spinning section. Besides, it is also important in fabric manufacturing
Objects of winding:
To transfer yarn from one package to another suitable package, this can be conveniently used for used for weaving process.
To remove yarns fault like hairiness, naps, slabs, foreign matters.
To clean yarn.
To increase the quality of yarn.
To get a suitable package.
To store the yarn.
Requirements of winding:
The requirements of winding may be summarized as follow:
     The fault level in the yarn must be reduced to an acceptable level.
     The yarn must not be damaged in any way in the winding process.
     The yarn must be wound in such a way as to permit unwinding in the following process with a minimum of difficulty at the required speeds.
     • The package size, shape and build must be the most technologically suitable for the particular end use.
     • The package size should be controlled to meet the particular economic requirements.
     • The winding operation must be geared to give the best possible economic performance of the whole process of fabric manufacture.
 Types of Winding:
     Precision Winding.
     Non Precision Winding. 
Precision Winding: 
By precision winding successive coils of yarn are laid close together in a parallel or near parallel manner. By this process it is possible to produce very dense package with maximum amount of yarn stored in a given volume.
  • Packages are wound with a reciprocating traverse. 
  • Patterning and rubbing causes damage of packages. 
  • Package contains more yarn.
  • Package is less stable. 
  • The package is hard and compact. 
  • The package is dense. 
  • Rate of unwinding of package is low and the process of unwinding is hard. 
  • The unwound coil is arranged in a parallel or near parallel manner.
Non Precision Winding: 
By this type of winding the package is formed by a single thread which is laid on the package at appreciable helix angle so that the layers cross one another and give stability to the package. The packages formed by this type of winding are less dense but is more stable.
  • Only one coil is used to make this package. 
  • Cross winding technique is used. 
  • The package density is low. 
  • Minimum number of yarn is wound. 
  • The package formed is soft and less compact. 
  • The stability is high. 
  • Flanges are not required. 
  • The rate of unwinding is high and the process is easy. 
  • The packages formed have low density.