What is Card Clothing?
The inclined wire set in base materials which are covered around the surface of taker in, cylinder, doffer and flat in the carding machine are called card clothing. The card clothing or ‘wire’ covering is critical. Without it the card is totally ineffective and the choice of card clothing for particular rollers within the machine is most important.
Card clothing is used on the surface of:
Taker in;
Cylinder;
Doffer;
Flat tops;
Stationary flats
Types of Card Clothing: Two types of card clothing are used today: flexible or fillet wires, and saw-tooth wires (commonly called metallic wires). Historically, flexible clothing was the first to be fitted to all card components. Metallic wire became prominent in the early 1960s with the increase in production rates from 5 to 20.5 kg/hr of cotton cards. Metallic wire is most commonly used as opposed to the original ‘flexible’ card clothing, which consisted of fine metal wires mounted in composite fabric foundations. Metallic wire is manufactured in continuous strips with a shaped profile that is stamped to create a single row of teeth. The ‘wire’ is wound around the card rollers under tension from one side to the other until the surface is covered with teeth of specific point density and geometry. Since flexible card clothing is now largely confined to the carding of natural fibres in the traditional textile industry and is rarely used in nonwovens, all references to card clothing in this section will be to metallic wire unless specifically stated otherwise.
Figure 1: Card clothing
There are different types of card clothing used for short staple and long staple spinning mills. However, they can generally be categorized into three major types.
a) Flexible Card Clothing:
These clothing have hook of round or oval wire which are set into elastic, multiple – ply cloth backings. Each hook is bent to a U-shape and is formed with a knee that flexes under bending load and returns its original position when the load is removed.
Fillet or flexible card clothings consists of foundation and wire, and are continuous strips of clothing 1-1/2 inches to 2 inches wide. Card flats are special fillets about 40 inches long mounted on cast-iron slats to enclose the upper portion of the card cylinder.
Advantage of flexible card clothing:
Point density being high, carding action is good.
Wire point flexible so fibre damage is less.
Fibre, yarn can produce.
Disadvantage of flexible card clothing:
Carding angle cannot be chosen.
Grinding action should be regular.
Foundation materials are required.
b) Metallic Wire Clothing: The real success in the development of increasing card production was owing to the introduction of metallic wires. In the manufacturing process, a wire with a round section is flattened and rolled into a long strip comprising (a) a rib to constitute the base of the wire, and (b) a thin web forming a portion for teeth. This thin portion is stamped or punched so as to leave a thin serrated strip called saw tooth wire. It is also frequently called rigid wire—an apt designation. The tooth thus formed is very solid, strong and sturdy.
Figure 2: Pattern of crowns in flexible wire
According to above figure 2, depending on the basic weave arrangement, the crowns and therefore the noggs are formed. The wires are pierced accordingly. The procedure is continued along the whole length of foundation strip. (a) Plain set. (b) Rib set.
The teeth are usually subjected to a special hardening treatment. It involves controlled heating followed by cooling. This enables the retention of sharp wire points for a longer duration. The base or the rib portion, however, is specially tempered so as to partially retain flexibility. This is essential because; the wires, when mounted on cylinder or doffer, have to conform to their peripheries. Unlike licker-in wire, the wires on the cylinder and doffer are simply put on their bare surface. However, like metallic wires on the licker-in, both the teeth and the base of these wires form an integral part of saw tooth wire. Metallic wires are mostly used in cards. The sharpness of the card clothing is very important for the proper processing of staple fibers.
Figure 3: Metallic card wire
Advantages of metallic card clothing:
Metallic wires clothing is more durable to flexible card clothing
High wear resistance
Requires Low Maintenance
Allows higher operating speeds
It is cost effective.
c) Semi Rigid Clothing:
In case semi-rigid clothing the sharp pointed wire are set in more rigid backings. This backing is made of multiple plies and the no of plies are more in number than that in flexible clothing. The wires have no knee & are deeply set inside the plies. The wires are much less capable yielding than flexible clothing. Semi-rigid clothing is found only in the flats.
Advantage of semi rigid clothing:
No need of sharpening after short use.
No dirt and dust in stored.
No need to of frequent grinding.
Grinding:
It is process of retaining the original position of cloth wire after using for a long time. Both, the delicate needle points in flexible clothing and the sturdy saw-tooth metallic wire points suffer heavily while carrying out the carding job. They lose their sharpness and become dull. The only difference between them is that the loss of sharpness with flexible wires occurs within 2–4 weeks (depending on the class of work), whereas the metallic wires become dull only after 7–8 months. The loss of sharpness weakens the hold of wires or saw teeth points on cotton fibers. This necessitates the grinding operation. This operation restores the good working condition of the wire points, by sharpening them and thus makes them ready for renewed and effective carding action.
Figure 4: Grinding of card clothing
Count of Card Clothing: The count of card clothing used for the cylinder depends on the yarn’s count:
Count the number of crowns per inch across the width of the fillet (e.g., 4).
A plain set will have a vertical repeat over two rows, whereas a rib set has a repeat over three rows. The repeat is called a nogg. Calculate the crowns per nogg (e.g., 4).
Count the number of noggs or repeats in one inch along the length of the fillet (e.g., 25).
As there are two points per crown, 300 × 2 = 600 wire points/in2 …………..1
Using eqn 1, we have,
…………………………………..Points per sq. inch
Count of Card Clothing = ———————————- ……………………………………………5
….600
= ————— ……5
= 120
It was customary to use the count of cylinder clothing ranging from 80s to 120s depending on the class of work. For coarse cottons, a lower count was used. The clothing on doffer and flats, especially on doffer, were usually a ten count finer than that on cylinder. It thus provided more point density on doffer. On a card with flexible clothing, this was purposely so chosen as to help easy transfer of fibers from the cylinder onto the doffer. It may be mentioned here that the plain weave pattern gives the highest point density amongst all the patterns. As against this, it may be noted that in metallic clothing, point density on cylinder is much higher than that on doffer. This is done to improve carding action. Further, the fiber-holding power of metallic clothing is very low, so the transfer of fibers from the cylinder onto the doffer is comparatively quite easier.
References:
Principles of Spinning: Carding and Draw Frame in Spinning By Ashok R. Khare
Handbook of Nonwovens Edited by S. J. Russell
Textile Handbook By The Hong Kong Cotton Spinners Association
Fundamentals of Spun Yarn Technology by Carl A. Lawrence
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
