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Questions and Answers
What is the primary focus in the assessment of hosiery yarn quality?
What is the primary focus in the assessment of hosiery yarn quality?
Why do some knitters in SMEs mainly test the count of yarn?
Why do some knitters in SMEs mainly test the count of yarn?
What is the drawback of using higher twist yarn in knitting?
What is the drawback of using higher twist yarn in knitting?
What does low twist yarn achieve in knitting?
What does low twist yarn achieve in knitting?
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What consequence does non-uniform thickness of yarn have on loop formation?
What consequence does non-uniform thickness of yarn have on loop formation?
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How does waxing affect cotton hosiery yarn?
How does waxing affect cotton hosiery yarn?
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What does tenacity refer to in the context of yarn?
What does tenacity refer to in the context of yarn?
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What is flexural rigidity related to in yarn?
What is flexural rigidity related to in yarn?
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What is the typical range of twist for continuous filament yarns in warp knitting?
What is the typical range of twist for continuous filament yarns in warp knitting?
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How does increasing the twist of yarn affect its tenacity?
How does increasing the twist of yarn affect its tenacity?
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What is one of the effects of high twist on yarn characteristics?
What is one of the effects of high twist on yarn characteristics?
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Why is lubrication applied during yarn preparation?
Why is lubrication applied during yarn preparation?
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What is the recommended amount of waxing during yarn preparation?
What is the recommended amount of waxing during yarn preparation?
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What effect does twist have on the diameter of filaments?
What effect does twist have on the diameter of filaments?
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Which property should be considered low for a yarn used in warp knitting?
Which property should be considered low for a yarn used in warp knitting?
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What is one recommended property of yarn for good warp knitting performance?
What is one recommended property of yarn for good warp knitting performance?
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What is the relationship between the level of twist in staple fiber yarns and their strength?
What is the relationship between the level of twist in staple fiber yarns and their strength?
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Why is high twist not desired in knitwear?
Why is high twist not desired in knitwear?
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How does the extension of staple fiber yarn compare to filament yarns?
How does the extension of staple fiber yarn compare to filament yarns?
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What problem does excessive yarn hairiness cause?
What problem does excessive yarn hairiness cause?
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What is the purpose of elasticity in yarn used for knitted fabric?
What is the purpose of elasticity in yarn used for knitted fabric?
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What is crucial for ensuring proper operation in knitting machinery?
What is crucial for ensuring proper operation in knitting machinery?
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What moisture condition is preferred for yarn in knitting?
What moisture condition is preferred for yarn in knitting?
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What are the two main types of yarn supplied to the Warp Knitting machine?
What are the two main types of yarn supplied to the Warp Knitting machine?
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What is one major advantage of filament yarns over staple fiber yarns?
What is one major advantage of filament yarns over staple fiber yarns?
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Which mechanical property is NOT mentioned as being more uniform in continuous filament yarn compared to staple fiber yarns?
Which mechanical property is NOT mentioned as being more uniform in continuous filament yarn compared to staple fiber yarns?
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How does the number of filaments in a yarn strand typically affect flexibility?
How does the number of filaments in a yarn strand typically affect flexibility?
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What does the yarn diameter primarily depend on?
What does the yarn diameter primarily depend on?
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Which statement about twist in yarn is true?
Which statement about twist in yarn is true?
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What is the relationship between the mechanical properties of filament yarns and denier?
What is the relationship between the mechanical properties of filament yarns and denier?
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What type of filament yarn is most suitable for outerwear fabrics?
What type of filament yarn is most suitable for outerwear fabrics?
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What factor significantly contributes to lint formation during knitting?
What factor significantly contributes to lint formation during knitting?
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Which yarn characteristic is least important for efficient running on knitting?
Which yarn characteristic is least important for efficient running on knitting?
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What major characteristics influence the choice of yarn count for a circular knitting machine?
What major characteristics influence the choice of yarn count for a circular knitting machine?
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What is primarily used to determine the yarn count on circular knitting machines?
What is primarily used to determine the yarn count on circular knitting machines?
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Which of the following fibers typically has the highest yarn count when using a 10 needles/inch machine gauge?
Which of the following fibers typically has the highest yarn count when using a 10 needles/inch machine gauge?
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Which of the following best describes the main performance characteristic of yarn during knitting?
Which of the following best describes the main performance characteristic of yarn during knitting?
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What common misconception relates to the properties of yarn during knitting?
What common misconception relates to the properties of yarn during knitting?
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Which property must a yarn possess to ensure it withstands cyclic stress and strain effectively?
Which property must a yarn possess to ensure it withstands cyclic stress and strain effectively?
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Which yarn property is essential for maintaining structure and form during the knitting process?
Which yarn property is essential for maintaining structure and form during the knitting process?
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What is the consequence of using a yarn with high initial stretch resistance in knitting?
What is the consequence of using a yarn with high initial stretch resistance in knitting?
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For circular knitting, what determines the range of yarn counts that can be used?
For circular knitting, what determines the range of yarn counts that can be used?
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Study Notes
Yarns for Knitting
- Yarn characteristics significantly affect the performance and appearance of knitted fabrics.
- Improvements in the knitting industry necessitate improvements in knitting machines and yarn optimization.
- Various hosiery yarns are manufactured using different fibers to suit varied end-uses.
- Cotton yarn is the dominant material for knitted products.
Yarn Count & Machine Gauge
- Yarn count selection depends primarily on the machine gauge (pitch).
- For a given machine gauge, yarn count selection can vary substantially.
- Knitted structure, desired fabric appearance, and fabric properties influence yarn choice.
Yarn Count and Machine Gauge Table
- Tables show various yarn counts (Ne) across different machines. (Specific values omitted for conciseness). This varies with different yarns and knitting types
Knitting Demands of Yarn
- Important yarn quality requirements (in order of importance) for efficient knitting are:
- High work of rupture value.
- Substantial elongation at break.
- Low flexural, torsional and initial stretch resistance.
- Good resiliency.
- Reasonable tenacity and loop strength.
- Resistance to fatigue.
- Regularity of physical characteristics (twist, evenness, moisture content).
- Smooth and low frictional properties.
Knitting Yarn
- Hosiery yarn quality assessment typically employs established weaving norms (with the exception of waxing).
- Yarn purchase is based on general parameters like count, imperfections, strength, elongation, and TPM.
- Many small and medium enterprises (SMEs) primarily test yarn count to determine fabric GSM.
Twist
- Ideal twist in hosiery yarns is minimal.
- In specific situations, higher twist can improve performance by reducing yarn breakage, although this comes at the cost of fabric quality.
- Knit structures are formed by bending yarn into loops and interlacing them.
- Yarn bulkiness contributes to smooth, well-defined loop curvature.
- Bulkiness eliminates sharp bends, improving fabric's resiliency and stretch recovery.
- Smooth curvature and high resilience are achieved via low twist yarns.
Uniformity
- Uniform yarn thickness and minimal imperfections produce a smooth loop.
- Thin yarn regions experience greater twist and form compact structures.
- Thickness variations result in changes to loop tensions, thereby influencing loop formation and dimensions.
Coefficient of Friction
- Waxing cotton hosiery yarns is prevalent.
- Waxing improves yarn quality, thereby reducing yarn friction.
Flexural Rigidity
- Flexural rigidity is the yarn's resistance to bending.
- Loop formation involves torsional, flexural, and tensile deformations.
Tenacity and Breaking Extension
- Tenacity is the specific stress at rupture, expressed as CN/Tex.
- Breaking extension represents the elongation at maximum strength.
- Sufficient yarn strength is essential to withstand tensile strain during knitting.
- Yarn strength influences fabric stability.
- Staple fiber yarn strength is largely proportional to the inserted twist.
- Higher twist leads to harder yarns, whereas knitwear primarily requires soft-twisted yarns, leading to a perpetual trade-off.
- Staple yarn extension is inversely linked to its twist level.
Yarn Hairiness
- Excessive hairiness increases yarn friction between metal components, hindering loop formation (especially with cotton yarn).
- Excessive hairiness leads to fabric imperfections and excessive pilling.
- Improper dyeing is often a consequence of hairiness.
Elasticity
- Elasticity is frequently mistaken for yarn or fabric extensibility.
- Yarn should not exceed its elastic limits during the knitting process to prevent permanent alterations.
Summary
- Warp knitting prioritizes yarn loading over strength, in contrast to weaving, emphasizing low friction and evenly distributed moisture content in the yarn.
- Elongation and elasticity are vital as is avoiding weak points to prevent stoppage.
Warp Knitting Yarns
- Two principal yarn types are continuous filament (regular and uniform) and staple, which may also involve fancy yarns or blend fibers.
Filament Yarns
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Filament yarns are very popular in warp knitting due to their uniformity, permitting smooth passage through precision-set elements.
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In high-speed knitting, lint is an excessive and problematic material.
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Filament yarn properties, such as tenacity, elasticity, flexural rigidity, and bending modulus, are often more uniform compared to staple yarns.
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Continuity, freedom from knots, and high pliability facilitate smooth loop formation.
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Properties are dependent on denier, filament number, specific gravity, and shape factor of the used synthetic material.
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Multifilament yarns exhibit increased flexibility and pliability relative to monofilaments of the same denier.
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Low-denier filaments are often included in multifilament yarn to decrease rigidity.
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Filament yarn types are specific to fabric types like outerwear (7-8 filaments) and underwear (10-13 filaments).
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Twist, a critical parameter, influences tenacity, elasticity, denier, and diameter, and is related to abrasion resistance.
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Twist levels range from 0-7 for many yarns. (50-60 tpi for special cases)
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Twist influences yarn properties like absorption and dye uptake, while affecting fabric drape and air permeability.
Lubrication
- Lubrication is typically employed to increase filament cohesion, lessen friction, enhance pliability, and neutralize static charges.
- Waxing is frequently applied and ranges from 0.5 to 2%.
Staple Fiber Yarns
- Staple fibers are less frequently used in tricot knitting, but more so in raschel operations.
- Only high-quality, properly twisted and gassed cotton, along with lubrication, is commonly used for knitting.
Important Yarn Properties for Warp Knitting
- Key warp knitting yarn characteristics include high work of rupture, good elongation, minimum tenacity, low bending/flexural rigidity and torsional rigidity, and high resiliency.
Wrapping
- Wrapping creates vertically-oriented patterns on jersey structures using warp threads.
- Controlled warp threads overlap into selected needle hooks leading to pure wrapping or embroidery plating in certain cases.
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