Answer: A yarn is a continuous length of interlocked fibers that is used in textile production. According to textile institute yarn may be defined as a product of substantial length and relatively small cross section consisting of fibers or filaments with or without twist.
2. What is staple yarn and filament yarn?
Staple yarn: a staple yarn is a linear assembly of fibers, where the individual fibers are small in cross-section and short in length; held together usually by the insection of twist, to form a continuous strand.
Filament yarn: a filament yarn is a linear assembly of fibers, where the individual fibers are small in cross section and very long in length, length may be 1 km long; little or no twisting may be required to provide required coherence to held together.
3. What is fiber fineness?
Answer: There are three most significant fiber characteristics: fineness, strength, and durability. A yarn’s fineness determines how many fibers are present in its cross-section. There should be at least 30 fibers in the yarn’s cross-section, but usually there are hundreds.
4. Explain yarn cv%?
Answer: CV means Co-efficient of variation. The variation in yarn count from one lea to the other lea can be measured by the Co-efficient of variation. It is expressed as a percentage.
5. What is yield point?
Answer: the point in the stress-strain curve at which the curve levels off and plastic deformation begins to occur.
6. Describe the reasons for blending different fiber in a textile product.
Answer: blends may be used to improve strength, to increase wash ability or soil resistance to increase dimensional stability or easy-care properties, or to provide a pleasing hand or feel. They may also be used to decrease product costs.
7. What is yarn twist?
Answer: twist is the spiral disposition of the components of a thread which is usually the result of relative rotation of the two ends.
8. What is cuticle?
Answer: The cuticle is the outermost layer of cotton fibers. The outer layer is composed of a waxy material that is only a few molecules thick. Cuticle adhesion to the primary fiber wall is facilitated by its waxy nature.
9. What is lumen?
Answer: Throughout the fiber, there is a hollow canal called the lumen. The secondary cell wall is composed of concentric spirals. The thickness of the lumen determines the maturity of cotton fiber.
10. What do you means by fiber morphology?
Answer: Morphology refers to the size, shape, and structure of materials or textile fibers. The morphology of a textile fiber can be divided into two types: macro-structure and micro-structure. Another type of structure is micro-structure, which describes the structure and appearance of microscopic longitudinal and X-sectional sections.
11. What is organic cotton?
Answer: In organic cotton, toxic chemicals are not used at any step in the growing process. To grow it, no chemicals, pesticides, or fertilizers are used, and the cloth is unbleached and dyed with natural plant dyes.
12. Is organic cotton more sustainable than conventional cotton?
Answer: In conventional cotton production, pesticides are overused and misused. This negatively impacts the environment and agricultural workers, and chemical residues on conventionally grown cotton can cause health problems such as cancer, skin irritation, and other conditions. But in organic cotton, there are no use chemical fertilizer and pesticides. Thus, organic cotton is an environmentally preferred product that benefits farmers, consumers, and the environment.
13. Write short note: Bio-tech cotton, coloured cotton.
Bio-tech cotton: Today’s biotech cotton is genetically engineered to be herbicide and insect resistant. Transgenes currently available for commercial production in cotton provide tolerance to herbicides and bollworm resistance. Bacillus thuringiensis is a very common soil bacteria that produces “cry” proteins. “Cry” proteins are toxic to certain types of insects that attack cotton, and their action is specific to these kinds of insects. The “cry” protein of Bacillus thuringiensis is only effective if it is consumed by the target insect. A biotech cotton plant is genetically modified to produce toxins that kill insects or resist herbicides, not to increase yields.
Coloured cotton: The natural color of cotton ranges from creamy to bright, light brown to mahogany, light green to green, and very light. While some genotypes may fade over time and with washing, others may not. After many washings, the brown color of some genotypes may intensify. Coloured lint usually has poor quality fibers, a higher micronaire, and a shorter length. Coloured cotton represents a niche market.
14. What is ginning?
Answer: The process to remove cotton fibers from the seed is called ginning.
15. Define mixing and blending with example.
Mixing: When same kind but different graded of fibers are mixed together then it is called mixing.
Example: high graded cotton+ low graded cotton= mixing.
Blending: When different types of fibers it may be equal or nearly equal graded are mixed together are within a particular ration then the mixture is called blending.
Example: 65%cotton+ 35% polyester= blending
16. What is bale management? Write three objects of bale management.
Bale management: The choice of cotton bales according to the fiber characteristics in order to achieve acceptable and economical processing condition and a constant yarn quality is called bale management.
Objectives of bale management:
A possibility reducing costs as a result of an improved knowledge of the fiber characteristics.
A mean of avoiding quality jumps.
An evening out of the quality characteristics of a yarn.
17. Write the definition of blow room with objectives.
Blow-room: The section where the supplied compressed bale is turn into a uniform lap of particular length by opening, cleaning, blending or mixing is called blow room.
Objective of blow room:
Further opening of compressed cotton bale and cotton are made into small tufts.
To eliminate dust, dirt, broken leaf, seed particles, grass and other foreign impurities from the fiber.
To produce a comparatively good quality cotton fiber by mixing different types of cotton together.
18. What is blow room line?
Answer: An arrangement of machines that perform every function to form a uniform lap from cotton bales is called a blow room line.
19. What is carding?
Answer: the reduction of entangled mass of fibers of filmy web by working them between two closely spaced relatively moving surfaces closed with sharp point is called carding.
20. Explain, “Why carding is called the heart of spinning”?
Answer: the first condition of spinning is to open the fiber at single stage and which is possible only by carding. The quality of the yarn specially depends on the carding action, so that carding is called the heart of spinning.
21. What is card clothing and stripping?
Card clothing: to cover the surface of taker in cylinder, doffer and flat of a carding machine with the help of a number of unlimited fine closely and specially bented wire is called card clothing.
Stripping: During the carding process, fibers and impurities become embedded in the teeth and wires of the several carding organs which may reduce their effectiveness of carding and quality of yarn. The process of removing adhering fiber and impurities is called stripping.
Flexible clothing : Flexible clothing is characterized by hooks made of round or oval wire set into elastic, multi-ply cloth backings. Each hook is shaped like a U and has a knee that flexes when under bending load and returns to its original position when the load is removed. In short staple spinning mills, this clothing is only found on card flats. There are between 240 and 500 points per square inch in the flats.
Semi-rigid clothing: The semi-rigid type of clothing is similar to the flexible type in terms of its structure. Although it has multiple cloth layers and sharp points with squared cross-sections, there are more and more cloth layers. It has the advantage that it is not choked with fiber, therefore less flat stripping occurs. Clothing that is rigid needs to be sharpened less frequently than clothing that is flexible.
Metallic clothing: In metallic clothing, teeth are cut at the smallest possible spacing by a process similar to punching, making the structure continuous and self-supporting. In the case of saw tooth clothing, large teeth are present, such as those found in a licker-in.
23. Write short note: carding action, stripping action and doffing action.
Carding action: when the wire points of two closed surface are inclined to the opposite direction and fiber tuft weight is reduced by the relative motion of the two surfaces then the action is called carding action. Carding action occurs between cylinder and flat.
Stripping action: A stripping action occurs when the wire points of two closed surfaces are inclined in the same direction and both surfaces rotate in the opposite direction. The cylinder and taker-in perform a stripping action.
Doffing action: The doffing action occurs when the wire points of two closed surfaces are inclined in opposite directions and both surfaces rotate in the same direction. Doffer and cylinder perform doffing actions.
24. What is drawing?
Answer: The process of passing the sliver between many pairs of rollers, each moving faster than the previous, in short staple spinning is called drawing.
25. What is drafting and drafting wave?
Drafting: the action of reducing the thickness or linear density of the feed material by drawing is known as drafting.
Drafting wave: The fibers in the sliver are not all the same length and are not perfectly straight and parallel. When this sliver is passed through drawing rollers the short fibers causes of an alternate thick and thin place due to their irregular movement through the passage. This thick and thin places gives a wave like surface in the sliver which is called drafting wave.
26. Why jute is called bast fiber?
Answer: From the definition of bast fiber we know that, “ the fiber which is obtained from the stem, bark or leaf of certain vegetables plants is called bast fiber. Jute is obtained from the bark of the jute plants, so jute is called the bast fiber.
27. What is batch and batching?
Batch: A blend of different types of jute is made up to suit particular class of yarns being spun, this blend is known as batch.
Batching: All the process from preparatory to carding includes in the batching. It is the primary stage of jute yarn processing.
28. What is emulsion and write standard emulsion’s recipe?
Emulsion: An emulsion is an intimate mixture of two immiscible liquids where one is dispersed in small globules on the other and addition of a third substance brings stability.
Standard recipe:
Water: 79.5%
Mineral oil: 20%
Emulsifier: 0.5%
29. What is clock length?
Answer: When clock pointer moves one complete revolution during this time feed roller feeds certain length of fiber. This length is known as clock length.
30. What is lead percentage?
Answer: The ratio of the difference between faster surface speed and slower surface speed to the slower surface speed expressed in percentage is called lead percentage.
31. What is dollop weight?
Dollop weight: When clock pointer moves one complete revolution during this fixed weight of jute fibers is feed to the machine. this fixed weight of jute is known as dollop weight. For uniform feeding, it should always be constant.
32. What is pilling or conditioning?
Answer: The process by which after applying emulsion jute is stored at a specific condition for certain time is called pilling.
33. What is count?
Answer: According to textile institute, “count is a number which indicates the mass per unit length or the length per unit mass of yarn”
34. What is ring spinning?
Answer: The spinning method that utilizes the roller drafting for fiber mass attenuation and the combination of freely circulating traveler around a ring to insert twist for consolidation and the produced yarn is wound onto a bobbin for suitable package formation is called ringing spinning.
35. Write the principle of the open end spinning system?
Answer: When the fibrous material is highly drafted or opened, it creates a break in the continuum of the fiber mass when the fibers are separated from the fiber mass. The fibers are then collected onto the open end of the yarn. Open end spinning or break spinning involves rotating a yarn to twist the fibers into the yarn structure and wrapping the yarn to form a package after spinning. As a result, winding and twisting occur simultaneously.
36. What is uniformity ratio?
Answer: Uniformity ratio is defined as the ratio of 50% span length to 2.5% span length expressed in percent. In a fibrogram, it shows the distribution of fiber length.
37. Write short note: trash, dust and neps.
Trash: Trash is the general term used for larger impurities. The impurities which cross-sectional size are bigger and rages as less than equal 500 micro-meter is defined as trash. The trash contains the particles from the cotton plant itself and other plants which contaminate the cotton field.
Dust: Dust is the general term used for smaller size impurities and microscopic particles. The impurity which cross-sectional size lies between 50-500 micro-meter is defined as dust. The dust contains the particles from the cotton plant itself and simply, dirt that generates from the cotton field and sticks with the plant during harvesting.
Neps: Neps are small entanglement or knots of fibers. Neps do not grow on the plant. Seed cotton does not contain any neps. But when dibers go through the mechanical
38. What is fiber maturation?
Answer: Fiber maturation is evident by desiccation of the fiber and collapse of the cylindrical cell into a flattened, twisted ribbon beginning 45 to 60 dpa. Most cotton fibers have aspect ratios, or length to width rations, in the 1000 to 3000 range. However, some matured fibers can reach up to 4000 times in length of their diameters. Both fiber length and secondary wall thickness are increased with higher potassium supply during growth.
39. What is grid bar?
Answer: The segment shaped devices which controls the amount of waste and grade of waste and are placed under the opening assemblies is defined as grid bar.
40. Write the basic principle of carding?
Answer: Carding involves following basics principles:
Reduction of the tufts into smaller sizes, termed tuflets.
Separation of each tuflet into individual fibers to form a filmy web, by working the tuftlets between closely spaced surfaces covered in sharp opposing points.
Consolidation of the web into a stable, continuous and transportable form of the fiber assembly, called a card sliver.
Removing trash, fiber fragments, very short fibers and neps during the reduction of tufts into fuflets and tuftlests into individual fibers.
41. What is delay factor?
Answer: Under steady state conditions in the taker-in-cylinder doffer combination, the number of revolution of cylinder required to remove the total load of fibers carried by the cylinder to the doffer is defined as the delay factor.
42. What is actual draft and mechanical draft?
Actual draft: The ratio of size of feed material to the size of delivery material is called actual draft.
Mechanical draft: The ratio of the machine’s linear speed of delivery roller to the feed roller is called mechanical draft.
43. What is creep and crimp?
Creep: When a load is applied on a textile materials then instaneous strain occurred in the fiber and after release the stress slow deformation will be occurred with passing of time. This behavior of textile fiber is called creep.
Crimp: The ratio of the difference of straightened length and crimped length to the crimped length expressed in percentage is called crimp.
44. What is correct invoice weight?
Answer: Correct invoice weight or conditioned weight refers to the weight obtained after standard moisture regain has been applied to the material.
45. Write the modern testing equipment for modern spinning mills.
High volume instrument (HVI)
Advance fiber information system(AFIS)
Shirley analyzer (used for trash%)
Moisture meter (used for MC%)
Moisture testing oven (used for MR%)
46. What is braking length?
Answer: The length of the specimen which will just break under its own weight when hung vertically is called breaking length.
47. What is plasticity of yarn?
Answer: After elastic limit when stress is increased the material can not recover the extension if stress is removed is known as plasticity.
48. What is moisture content (MC) and moisture regain(MR)?
Moisture content: The ratio of water in a material to the total weight of the material expressed in percentage is called moisture content.
Moisture regain: The ratio of water in a materials to the over dry weight of this material expressed in percentage is called moisture regain.
49. What is Relative humidity?
Answer: The ratio of the actual vapour pressure to the saturated vapour pressure at the same temperature express as a percentage is called as relative humidity.
50. What is micronair value?
Answer: weight in micrograms per inch is called mocronaire value. The micronaire value regarded as identification of maturity and fineness.
In this article, I tried best to present 50 most important question and answer of yarn manufacturing for textile’s competitive exam. If you have any question, please comment here.
Kazi Rashedul Islam is an “Assistant Technical Officer” at the Textile Engineering department at Jashore University of Science and Technology (JUST). He achieved his Bachelor of Science in Textile Engineering from Dhaka University of Engineering & Technology (DUET) in 2018. In 2012 he completed a Diploma in Textile Engineering degree from Begumgonj Textile Engineering College(TECN), Noakhali.
