Monday, December 21, 2009

Soft Package Winding

The winding technology
The soft package winding is the most important pre dyeing operation ,which directly affects not only the dyeing quality but also post dyeing operations such as rejects,wastages and poor unwinding ,thread breakages etc.Well wound is half dyed, is the popular saying which is very correct in the context of package dyeing ,because we cant expect miracles from the most advanced dyeing machinery ,if our packages are of poor quality. Although different technologies of winding when operated carefully provides satisfactory results ,but in order to insure uniformity and consistently good winding ,precise adjustment and careful maintenance of the equipment is necessary and the operators must be trained and closely supervised.
Factors like count of the yarn, angle of winding, yarn tension during winding, diameter and traverse of the package, the stability of the package, the winding ration,the compactness and size of the feed package all affect the package make up and must be considered while selecting a machine for soft package winding.Hard and soft places can occur within a single package if a poor winding is chosen ,causing some parts to dye lighter or heavier.The most compact part of any package is edges or shoulders ,where the yarn turns the corner and this is the most difficult place to wet out and to penetrate.incomplete penetration will cause will cause it to dye lighter or not at all,Cupping or crimping is the only workable solution to this problem.

What is crossing or Winding angle 
It is the angle at which the yarn cross each other on a wound package, smaller the crossing angle denser will be the package.
What is a winding ratio ?
It is number of turns of yarn per revolution of the package, or distance between the threads of layer. More the number of turns per revolution more is the density. Increasing the distance between the threads of a layer decreases the density.
What is package stability ?
It is the tendency of wound yarn on the package holder to remain stable. It the yarn layers does not hold good on the package holder ,the package may deform easily in subsequent processing. For example on precision winding machines the winding angle reduce with increase in package diameter thus making the packages a little bit harder from outside layer, which may fall off during handling.




There are two different types of winding machines are available now a days,
1.Random soft package winding machines
2.Precision winding machines

The Package
The yarn to be dyed is first to be wound into a package .The weight and diameter of the package is limited by the space available between the spindles (pitch) and by the levelness obtainable when a dyeing is carried out using a particular dyestuff. The package dimensions and weight are influenced by the type and construction of yarn to be processed, class of the dyestuffs , machine flow rate ,end use of the dyed substrate and package holder eg spring ,cheese or cone. 
                                         Image:A package wound on compressible SS Spring
                                                A package wound on Rigid plastic cheese
   Yarn wound on SS cones

The yarn package must be stable enough ,to withstand the handling during loading, processing and unloading from the machine. It should withstand the temperature change and flow volume and flow direction of liquor. It should accommodate a small amount of shrinkage and swelling during processing with temperature increase as well as wetting.

Package Holder
The package holder may be a ss dyespring ,a perforated plastic cheese (reuseable or disposable) or perforated cones made of SS or plastic.
Each and every holder type has advantages and disadvantages which are explained below,
A dyeing package is characterized by its geometry and its density profile , the bigger dia dye center has advantages over the smaller ID packages because it offers lesser resistance to the flow of liquor in case of in to out and at the same time area exposed to dye liquor is gtreater for better uniformity of the dyeing.
As a thumb rule the main objective from the dyers point of view is to get the material uniformly dyed throughout the package, the machine is used to its full capacity ,the hydro extraction and drying is done without affecting the quality of the dyed material and unwinding is trouble free.





SS Dye Springs
The dye springs are most commonly used package holder ,on which the yarn is wound offers the advantages such as these are reusable ,compressible ,making a perfect coloumn after pressing,spacers etc are not used between the individual packages ,thus reducing the possibility of channeling , dye spring offers much lesser resistance to the liquor flow through the packages. Due to the higher compression possibility the dyeing machines can be loaded to a higher capacity and liquor ratio can be reduced for better economy of the process.

The main disadvantage is the higher initial investment, in some cases due to the shrinkage of the yarn channeling takes place which causes uneveness and poor unwinding behaviour at bottom particularly ,a thread reserve is difficult to restore due to pressing in case of dyesprings and replacement /repair required due to damage of lacing wire and deformation during use.

Cones
Conical dye packages have conventionally being used for their comparatively good run off behaviour .

The material to be wound on the SS or polypropylene cones of adequate weight and dimensions and taken for dyeing . Generally spacers are provided between each individual cones to make the dyeing column .The biggest advantage of cones is considered to be their subsequent use in next operation without rewinding, however these are no more popular due to their numerous disadvantages, such as




Use of spacers is itself a big problem ,which causes the liquor blow out at the joints.
The liquor flow through the cone is also not uniform due to the different dimensions at the bottom and tip of the cone. The dye center is defined by the cone tip ID ,which also reduces the liquor flow .The solid cones also pose more resistance to the liquor flow resulting in unlevel dyeing results. There is much more space remains unutilized due to the shape of the cone which reduces capacity utilization and also higher material to liquor ratios. The solid cones can not be compressed ,hence the machine remains under loaded.
Perforated Plastic and SS Dyetubes



These tubes are an alternative to the dye springs ,are made of polypropelene material , either for multiple use or single use or Stainless steel. These are available either radially compressible or axially compressible type, which are very cheap and can be disposed off after single use. Winding is uniform and perfect on the perforated dye tubes due to accentrical design of the tube.The flow through the package is Improved, with radiused holes The perforated plastic tubes are available in various colors to identify denier and thread , different qualities can be processed simultaneousily without fear of mix up.Consistent dimensions and remains intact when used properly Built-in M/F adaptor ends eliminate need for separators and perfect fitting minimize the chances of liquor blow out at the joints. The density of the dyeing column is governed by the individual packages and hence it can be controlled at the winding stage itself. The thread reserve remains intact because these are not compressed. The dyeing cheeses are suitable particularly in case of materials which are delicate in nature and having higher wet shrinkage properties.




The main disadvantage of perforated solid tubes is non compressibility ,which reduces the loading and hence machine capacity. The yarn generally slough off in case of the yarns which got relaxed after heat treatment. These are easily damaged if the hydro extraction facility is not upto the mark. If winding and density are not uniform within a package and package ,the dyeing results would be poor.
Package weight and density
The package weight and density are two important parameters which are to be standardized for uniform and trouble free dyeing .The packages may be soft or hard these should conform to the standards,when too soft liquor flowing through it will find the course of least resistance and cause channelling ,which leaves some parts of the package relatively undyed or lighter. If the packages are wound too hard ,a point can be reached where the flow of liquor is impeded to such an extent that poor dyeing or none may occur.The package weight and dimensions depends upon the type of the machine ,its flow rate ,automation, type and construction of the yarn to be dyed, dye class to be used and type of package holder to be used.The typical density norms for different type of yarns is between 350-450 gm/ltr.The most important requirement of soft package for dyeing are,
1.Density of the package should be uniform throughout of the package diameter, ie the layer to layer density is controlled.
2.The packages should not have the hard edges ,or these must be broken or cupped by a suitable device or manually.
3.The package weight must be controlled and all the packages must fall within the standard norms.
4.The density variation from one package to another must be controlled statistically and CV5% should not exceed 5%
Following factors affect the flow of liquor through the packages
1.Yarn or filament fineness:-The permeability increases with increase in the yarn diameter.
2.Yarn twist:- The permeability decreases with the increase in the twist .Low twisted yarns can adopt a flat rather than circular shape ,which makes the packages more permeable.




3.Winding ratio :- More the number of revolutions per round of package makes the package less permeable.
4.Winding angle:- The smaller winding angle makes the packages less permeable.
5.Yarn tension in winding:- The higher the yarn tension in winding makes the package harder and denser and hence less permeable.
6. Swelling and Shrinkage:- The higher swelling and shrinkage during dyeing makes the packages less permeable.
How to calculate the package density

The package density is expressed in gm/cc or gm/ltr
Let the gross weight of the package = W1 gms
The weight of the cheese/spring = W2 gms
Net weight of the yarn W = W1-W2 gms
Hight of the package in cm = h cm
Outer radius of the cheese /spring = r1 cm
Outer radius of the package = r2 cm
Volume of the package V = p (r22 – r12 ) h CC




Density of the package = W/V gm/cc

The density of the cone is also expressed in gm/cc or gm/ltr 
How to calculate the cone density

Let the Gross weight of the package is =W1
The weight of the empty cone is =W2
Net weight of the cone W = W1-W2 gm
The perpendicular height of the cone = h cm
The radius of the cone at bottom = R1 cm
The radius of inner cone at bottom =r1 cm
The radius of the cone at top =R2 cm
The radius of inner cone at top =r2 cm
The volume of the cone is V =1/3 p h {(R12+R22+R1R2)-(r12+r22+r1r2)} ccThe density of the cone is D = W/V gm/cc
Random soft package winding machines

Random soft package winding machines are conventional winding machines ,in which a grooved drum acts as both the driving as well as the traversing element. The winding is done through indirect drive to the package ,which we call the friction drive. The yarn lay formed is random ,that’s why is called random winding.






The main characteristics of random winding are
1.Winding angle(a) :-Since grooved drum is used for winding the winding angle remains the same.
2 Winding ratio :-The number of coils per turn of the package decreases as the diameter of the package increases, so the package is softer at the outer layers.

3.Ribbon formation may occur at certain points within the package when diameter of package reaches to a certain ratio to drum diameter.

4.The package stability is good.
5.Layer to layer density is not very uniform throughout of the package.
6.Hard edges formation may occur at the yarn turning at the ends.

7.The machine speed can not be very high ,because it is very difficult to maintain good density profile at high speeds on random winding machines.
8.Cost of the machine is low.
However when selecting a random winding machine for Soft package winding we should look for following features
1.Ribbon breaking or anti patterning device
The machine must be equipped with a good and effective anti patterning device ,which will minimize the ribbon formation. The ribbons formed during winding not only results into poor dyeing due to liquor flow obstruction but also cause problems in unwinding by creating high tension zones and resulting into thread breakage, high hairiness due to increase friction and wastages. However it is impossible to overcome the ribbon problem completely.
2.Hard edges formation 
Due to the nature of friction winding with the groove drum ,the yarn stays for a relatively longer time at the edges ,and creates edges hard. The machine must be equipped with a proper arrangement in which the cradle or the bobbin holder slides slightly (by few mm) on the drum through a lateral movement device which reduce the chances of hard edges formation by widening the edge area.
3.Traverse of the package




While winding particularly on the solid perforated cheeses ,we should take care that the perforations on both the sides are covered completely and equally. If these are not covered equally there may be un Dyed parts if yarn is wound on blind areas and channeling may take place ,when there is no winding on a particular end.
4.Weight release mechanism
Since the weight of package increases with the increase in the diameter of the package which increase the cradle pressure on the drum and affects the density of the packages. Therefore the machine must be equipped with a proper weight release mechanism to balance out the increased package weight. (new machines are equipped with a programmed cradle weight regulation system)
5.Length measuring device
The machine must be equipped with a good length measuring meter control system to control the package weight variation .The uniform package weight helps in reducing the losses weight variation in dyeing and also reduce the chances of excess dyeing and short falls.
6.Balloon breakers
The machine must be fitted with an adequate balloon breaking device ,which provide more flexibility to use different size of feed packages and also reduce the breakages rate
7.Yarn tension controlling

It is very important that the machine have a good yarn tension control system ,that will insure the uniform package density within the package and package to package.
8.Winding Speed
The winding speed is also a constraint in random winders ,but now machines are available with individual drum drives which can run at speeds and it is also possible to make soft packages on automatic winders which can run upto 1400 mtr/min. The cost, flexibility of running different counts etc. and quality parameters must be considered in this case.





Precision winding


                                                       a precision wound package
In precision winding the package or dyeing spool is driven through a spindle with the help of an individual motor and yarn is displaced with the help of a guide or propeller blades( yarn laying system with counter rotating blades),there is is no slippage in the device or uncontrolled displacement of the yarn ,therefore it is called precision winding.
These machines are equipped with electronic or digital yarn tension control devices which vary the tension as the diameter of the package increases ,so that the layer to layer density remains the same. Each drum is driven through an individual motor which in combination with a micro computer controlled meter counter ,results into much more flexibility of operations.The machine productivity is high due to high running speeds and lesser labour is required to run the machine.
The main features of the precision winders are,
1.Since propeller blades or guide is used for yarn displacement the winding angle does not remains the same and decrease with the increase in package diameter.


                                             image :-rotating propellers yarn guide system
2.The number of coils per turn of the package remains same as the diameter of the package increases because the number of displacement remains constant per rotation of the package.
3.There is no ribbon formation.
4.The package stability is moderate.
5.Layer to layer density is very uniform throughout of the package.
6.Hard edges formation do not occur at the ends.
7.The machine speed is high .
8.Cost of the machine is medium to high.
Hybrid winding
The recent advancement in the precision winding technology is step precision winding or DIGICONE winding ,which ensures the perfect winding of packages by eliminating the technological problems of both the random winding and precision winding.

                                       A Digicone wound package
1.The winding angle remains almost constant.
2.The winding ratio is also constant
3.The package stability is good.
4.Density does not change with diameter.
5.No ribbon formation.
6.Very good unwinding performance.
7.The cost of the equipment is high.
What is the best combination
Technologically and from the dyers and post dyeing point of view the precision winding machines with a digital tension control device and solid perforated plastic cheese is the best combination to achieve
1.Uniform package to package weight and density.
2.uniform layer to layer package density and for all the packages.




3.Unintrupped flow of liquor through the package.
4.No yarn tension variation due to pressing disturbances and smooth and break free unwinding.
5.Thread reserve remains intact for further applications.
6.Optimum utilization of the dyeing machinery.
Further Reading on soft package winding




6 comments:

  1. Very Informative Blog. Great Job.

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    It is a critique on Yarn dyeing machines and winding machines and you may find it interesting

    regards
    Atul

    ReplyDelete
  2. Its really a good & informative......

    Stainless Steel Dye Spring Manufacturers
    Auto Yarn, Bangalore, India.

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    Replies
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      Its really nice to see your comment here.

      Santhanam

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