Roller Card in Carding for Non-woven and Wool Carding
Dept. of Textile Technology
Sarvajanik College of Engineering & Technology, Surat, India
Carding is a mechanical process that disentangles, cleans and intermixes fibers to produce a continuous web or sliver suitable for subsequent processing. This is achieved by passing the fibers between differentially moving surfaces covered with card clothing. It breaks up locks and unorganized clumps of fibre and then aligns the individual fibres to be parallel with each other. In preparing wool fiber for spinning, carding is the step that comes after teasing.
The proverbs of the experts “The Card is the heart of the Spinning Mill” and “Well Carded is half spun” demonstrate the immense significance of carding for final result of the spinning operation.
The opened and blended fibres then undergo carding process. The functions of the carding process are
- Individualization of fiber tufts to almost single fiber
- Mixing of fibers to average out variations in fiber characteristics
- Forming a homogenous web of uniform weight per unit area
Roller Card in Carding
1. For Non-Woven
In the case of short staple system, the revolving flat card is used, but for long staple system the roller top card is used in carding. As the dry-laid process mostly utilizes the long staple fibres the roller top card is often seen to be used in the nonwoven industry. Figure 1 displays the diagram of a roller top card. Though this card is similar to the revolving flat card in its basic features, but it differs from the flat top card in several respects, including the fact that their main carding fields are designed differently. The flats are replaced by pairs of rollers, as shown in Figure 1;
Thus the name “roller top card” is given to it. Each roller–pair comprises a “worker (or roller)” and a “stripper (or clearer)”. Together with the cylinder surface, they form a “carding triad.” The typical locations of the roller pairs and their directions of motion are also shown in Figure 1.
The basic principles of carding process are lying in carding action and stripping action. The disentangling of fibres is done by carding action and the transfer of fibres is done by stripping action. In order to realize the carding action between two surfaces, the wire points of the two surfaces must have opposite inclination, but in order to realize the stripping action between two surfaces, the wire points of the two surfaces must have the same inclination. This is illustrated in Figure 2.
For carding action, the movement of the surfaces should be in either opposite or same direction. When in same direction, the surface charged with material should move faster in the direction of inclination of its wire points.
Besides the carding and stripping action, the feeding, doffing, and web forming are also important and many interesting developments have been taken place in these regions so far,
There exist two feed arrangements: dish feed arrangement or roller feed arrangement AS SHOWN IN FIG 3.
The dish feed arrangement results in relatively harsh treatment to fibers, but the roller feed arrangement results in relatively mild treatment to fibers. The position of clearer roller depends on whether the taker-in is down-striking or up-striking.
Also, there are advancements going on in the doffing region. The double doffer system (IN BELOW FIG 4) tends to increase fiber transfer from cylinder to doffers, thereby increase production.
However, the top doffer takes away more material than the bottom doffer that may cause to differ tension in the respective webs which ultimately affect the structure and properties of the final nonwoven fabric. To balance the proportion of fibers taken by each doffer, different diameter, tooth density and setting between doffer and cylinder are adopted.
Further there exist four doffing systems for different orientation of fibres in the carded webs (Figure 5). The conventional cylinder-doffer system (Figure A) produces webs with markedly anisotropic orientation of fibers in plane. A randomizer roller in Figure (B) changes the direction of flow of fibers moving at high velocity resulting in almost isotropic web structure. A pair of condenser rollers (C), moving slower than the doffer, causes sudden deceleration of fibers that results in fibers to stand up vertically, creating a 3D “condensed” web structure with almost isotropic orientation of fibers in plane.
The web formation region is also of interest for R&D. The oscillation frequency of the doffer comb is technologically limited, which in turn limits doffer speed, hence production. High production cards run doffer at 25-40 rpm where the doffer comb can’t be used for stripping, but draw off rollers whose surface speed is slightly higher than that of doffer can be used to remove web through stripping action. More advanced doffing system utilizes a draw off roller, perforated apron and suction system to control web transfer to the apron
Productivity of older roller cards is about 30-50 kg/hour at the width of 1.5~2m. Nowadays, the roller cards of performance up to 1000kg/hour in width 2~3.5m are delivered. Flat carding machines are usually 1m wide and process about 5~50kg/hour.
Garnetts are similar to roller-top cards. R.L. Street has described the garnett as “a group of rolls placed in an order that allows a given wire configuration, along with certain speed relationships, to level, transport, comb and interlock fibers to a degree that a web is formed.” Garnetts are mostly used to process waddings and for making pads for automobile and bedding industries. It delivers a more random web than a card. Most webs from garnetts are layered by crosslapping to build up the desired finished nonwoven weight.
2. For Wool Carding
Worsted yarns are made from virgin wool fibres. The blending process is followed by scouring and drying, to rid the wool of its fat, suint and dirt.The clean, moist wool theb passes through one of two processes; it is either “prepared” or “carded”. The choice is determined mainly be the length; if this is longer than seven inches it is prepared, if shorter it is carded.
The carding actions falls into three categories:
- Point to point, a fraction of fibres being retained by both surfaces (worker/swift,doffer/swift)
- Point to back, all fibres removed from one surface to another (worker/stripper,stripper/swift)
- Back to back, fibres raised from one surface by another (fancy/swift)
The clothing on card rollers falls into two categories, metallic (sawtooth) wire and filletwire. Metallic wire resembles a fine saw blade, while fillet wire consists of staples insertedinto a flexible foundation (Figure-7). Metallic wires are more commonly found in the feedend of the card (feed rollers, lickerin roller), while the fillet wire is used in the swift section of the carding machine.
Some Specification of Worsted Roller Card
Some Manufacturer of Roller Card for Carding:
- Trützschler Nonwovens;
- Garnett Card Clothing;
- Ramella Pietro;
- Bekaert Non-Woven Card Clothing;
- Deeco Mechatron Mktg. Pvt. Ltd.;
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