Tuesday, December 24, 2019

CARDING PROCESS PARAMETERS,



CARDING PROCESS PARAMETERS:

The selection of correct process parameters is a very important and critical task in any process.  The right selection always gets reflected in the form of better quality of yarn in the carding process. The production cost also reduces with the correct process parameters. 

The some common and the most important process parameters are given below:

Specifications of cylinder wires clothing.

Specification of flat tops wire clothing. 

Specifications of licker-in wires clothing.

Specifications of doffer wires clothing.

Draft between feed roller and doffer.

Cylinder, flat tops, doffer and licker-in wire’s life.

SPECIFICATIONS OF CYLINDER WIRE’S CLOTHING: 

The specifications of cylinder wires play effective and decisive role in carding performance. The specifications are selected more precisely according to the quality of raw material to be processed, cylinder speed and rate of production of carding machine.  The characteristics to be considered in selection of wires of cylinder are given below:

Front angle of wire. 

Tooth profile.

Tooth pitch. 

Rib thickness (width).

Wire population.

Tooth point.

Tooth depth.


Front angle of wire:

The front angle of cylinder wire is selected according to working speed of cylinder and fibre to fibre cohesion force acting in the material to be processed. The degree of front angle is inversely proportional to working speed of cylinder. Higher cylinder speed requires lower front angle of wire for a given fibre. Higher production rate requires higher cylinder speed. Thus higher production needs higher space in the wires.  

 Higher speed of cylinder creates higher centrifugal force. This force tries to eject the fibre from the cylinder, along with the trash.  This centrifugal force affects the wire’s front angle. A cylinder having low front angle of wire and working at very low speed gives poor quality in processing of material of high frictional force. This poor quality is found due to less fibres transfer from cylinder to doffer. In this way, recycling of fibres takes place, which results in the form of more neps and entangled fibres. 

Tooth profile:

The new profile with less free blade avoids loading of the cylinder with fibre and trash. This helps in keeping the fibres at the tip of the tooth. The movement of the fibres towards the tip of the tooth coupled with centrifugal action demands an acute front angle to hold the fibre in place during carding.

Tooth pitch:

 Since the fine fibres or long staple fibres has very low stiffness, so that such kind of fibres need more control during carding process. This control is achieved by choosing the correct tooth pitch. This tooth pitch provides the correct ratio of the number of teeth to the fibre length.  Short fibres and fibres having less stiffness require less tooth pitch. 

Rib width:

The rib width decides the number of points across the carding machine. The rib width is selected on the bases of fibre characteristics and rate of production of machine. The finer fibres need finer rib width. The finer rib width  is selected for higher rate of production.

Wire population:

The product of the rib thickness and tooth pitch is called the population of a wire. Generally higher production rate needs higher  population of wires. 

Tooth point:

The sharp tooth points penetrate the fibre tuft more easily and help to increase the carding action. The cut-to-point wires are sharp and they have no land at all. 

Tooth depth:

The effective working depth of a cylinder wire tooth for cotton is approximately 0.2mm and for synthetic materials approximately 0.4mm. The man - made fibres require more space in their cylinder wire than cotton. More tooth depth allows the fibre to recycled, resulting in damaged fibres and neps. If tooth depth is insufficient, fibre control is lost. This results in even greater nep generation. 

SPECIFICATIONS OF DOFFER’S WIRE’S CLOTHING:

The specifications of doffer’s wire are given below:

The main function of doffer in the carding machine is fibres stripping from cylinder.  This stripping action is also called carding action.

The front angle of doffer wire greatly affects the fibre releasing from cylinder. An optimum angle of 60° is used to achieve better stripping of fibres

The wire population in doffer is kept below 400 ppsi to achieve better quality of yarn. 

The doffer wire height is kept 5 mm. in carding machine having small doffer. This wire height improve transfer of fibre from cylinder to doffer.

The fibre friction and high doffer speed greatly reduce the fibre holding capacity of doffer. Therefore wires with striations are used to achieve better result in the carding process. 

SPECIFICATION OF LICKER-IN WIRE’S CLOTHING:

The fibre to fibre opening is achieved by the licker-in. The cotton tufts are open fully with the help of licker-in. A licker-in wire angle of 85° is generally used for the processing of synthetic fibres as well as medium and long staple cotton.

A wire angle of 80°gives better performance in the processing of coarse and dirty cotton fibre. 

The hardness and strength of wire and sharpness of wire points have very big impact on the performance of a carding machine. The wires of licker-in never grind.

The thinner blades efficiently reach deeply into the fibre tuft. The wire’s life is also increased. 

The higher number of wire row per inch in licker-in gives better results. Today licker-in has up to 12 wire rows per inch. It gives better performance than licker-in having 8 wire rows per inch. 

If the wire pitch is not insufficient, the wire pitch is compensated by increasing licker-in speed, higher licker-in speed causes fibre rupture. The licker-in speed varies according to rate of production and types of fibres to be processed. 

SPECIFICATIONS OF FLAT TOP WIRES:

The specifications of flat tops to be used commonly in the carding process are given below:

The use of flat top having more than one population gives improved carding performance. 

The combination  of 80/450 is uses in the flat top generally. This combination gives better performance in the processing of both the materials (cotton and synthetic fibres). The rigidity of fillet is used according to material to be processed. Different fillet rigidity is used in cotton and synthetic fibre.

The number of wire points on stationary flats is very important factor in carding production. Normally, the number of wire points varies between 300 to 400. 600 number of wire points are used in high production rate carding machine.

If flat tops using in the processing of cotton are used for synthetic fibres processing, more heat is generated due to load on the cylinder. Hence high static charges develops and the chances of cylinder loading are increased.

Semi rigid flat tops give better performance in the processing of synthetic fibres. 

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2 comments:

  1. Thanks for sharing the best information and suggestions, I love your content, and they are very nice and very useful to us. If you are looking for the best Fibre Installation South Africa, then visit Accelerit Premium Fibre. I appreciate the work you have put into this.

    ReplyDelete
  2. Please refer to your quote in FRONT WIRE ANGLE last para......
    "This poor quality is found due to less fibres transfer from cylinder to doffer. In this way, recycling of fibres takes place, which results in the form of more neps and entangled fibres."

    If so then how does lower delivery speed always results good sliver quality ?

    ReplyDelete

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