Yarn Production Theoretical Aspects

This new text provides a comprehensive but introductory guide to key theoretical aspects of yarn production. It summarizes, unifies and explains a large body of recent literature devoted to theoretical and experimental studies of this area of textile technology. The basic analytical tools provided will be useful to textile engineers in quantifying the solutions to a whole range of textile processing problems. Two introductory chapters provide a foundation of practical information. The first is a 36-page review of present-day yarn production technology, including a discussion of fiber properties and sources, the principal methods of yarn production and their underlying principles, and yarn formation. The second introductory chapter covers the forces that act on fibers and yarns in the course of processing, and the effect and use of these forces in fiber alignment and straightening. Following, basic areas of yarn production theory are examined: drafting theory, fiber blending, ballooning theory, and tension and twist changes along a threadline. Analytical tools and simplified solutions are provided for each area of theory. The text is supplemented by more than 90 diagrams, flowcharts, graphs and other schematics that illustrate processes and theoretical concepts. The information in this new text will be useful to textile process engineers involved in fiber and yarn production.

Table of Contents:
Preface 1. Outline of the Technology of Yarn Production: o Introduction o Fibre Properties and Sources o Impurities Present in Cotton and Wood o Modern Yarn Production: General Principles, Systems of Yarn Manufacture, Preparation of Carding (Opening, Cleaning, and Blending), Carding, Preparation for Spinning, Spinning, Combing, Man-made-fibre Sliver Preparation, Rewinding of Yarn, Yarn doubling o Methods of Inserting Yarn Twist: Cost, Conventional Spinning, Unconventional Spinning o Continuous-Filament Yarns: Introduction, False-twist Texturing, Air-jet Texturing, Stuffer-box Texturing o Appendix 2. The Forces Acting on Fibres and Yarns: o Introduction o Air Drag on Fibres and Yarns o The Straightening of Individual Fibres by Means of Air-drag Forces: Practical Considerations, Acceleration of Fibres by Air Drag, The Straightening of Fibres by Laminar Air Flow, The Straightening of Fibres by Means of an Accelerating Air Flow o Magnitude of Electrostatic Forces on Fibres o Friction of Fibres and Yarns o Friction of Fibres and Yarns o Friction of Fibres against Pins: Outline, Friction between Fibres and Pins-Relative Movement, Force between Pins and Fibres in Tuft Form, Forces between Pins and Fibres in Slivers 3. Drafting Theory: Part I-The Determination of Drafting Force: o Introduction o Forces Between Fibres: Contact Pressure o The Force Needed to Remove a Fibre from a Sliver o Relationship between Load and Compression of a Sliver o Relationship between Load and Compression of a Sliver o Drafting Force: General Formulation o Drafting-force Calculations for Roller-drafting with Fibre-control Systems 4. Drafting Theory: Part 2-The Irregularity of Random and Perfectly Drafted Slivers: o Introduction o Irregularity Properties of the Random Sliver: Classification of Properties, Total Variance, Auto-correlation of the 'Thickness", Variance-Length Curve o Spectrum o Medium- and Long-term Irregularity of "Real" Slivers: Introduction, Perfect Drafting of Slivers o The Effect of Open-loop Control on the Output Variance-Length Curve o Perfect Drafting: Short-term-irregularity Changes, Reverse-drafting and the Random Yarn 5. Drafting Theory: Part 3-Imperfect Drafting: o Causes of Non-perfect Drafting o Fibres Moving out of Turn: "Stationary" Fibre Movement (Movement whose Pattern Remains Constant), Non-stationary Fibre Movements o Movement of Fibres in Groups: General Principles, Fibre Grip in Front Rollers Producing Fibre Groups, Irregularity Due to Change in the Nip Point o Irregularity Produced by Deformation of the Whole Sliver o Summary and Conclusions 6. Blending of Fibres: o Introduction o Blending by Doubling and Drafting: Definition of Blend Parameters, Effect of the Number of Doublings on the Blend Parameters, Theory of Blending by Doubling: Some Experimental Findings, The Index of Blend Irregularity o Blending on the Card: Introduction, Degree of Blending: Delay Factor, Over-all Smoothing Effect of the Card o Requirements of Batch-blending o Irregularity Parameters and Yarn Quality: Introduction, The Coefficient Variation and Variance-Length Curve, Spectrum of Yarn Irregularity, Blend-irregularity Parameters 7. Balloon Theory-Part I: Approximation Solution: o Introduction o The Tied Balloon in a Vacuum: Derivation of Basic Equations, Solution of Tied Balloon with Constant Tension, General Solution of Tied Balloon in a Vacuum o Modification of Tied-Balloon Solutions to Allow for Air Drag o The Complete Geometry of the Tied Balloon with Air Drag, Comparison Between Tied Balloon and Complete Solution When Applied to Conventional Spinning o Appendix: The General Solution of Equations 8. Balloon Theory-Part 2: The Application of the Approximate Theory to Conventional Spinning: o Introduction o Ring Spinning: The Limiting Balloon Size, The Effect of Control Rings, Tension in Ring Spinning o The Application of Balloon Theory to Cap Spinning o Appendix: The Ration of Balloon Tension to Winding-on Tension in Ring Spinning 9. Balloon Theory-Part 3: Exact Solution with Applications to Winding and Unconventional Spinning: o Introduction o Exact Solution to the Problem of a Rotating Thread o Application of Balloon Theory to Unwinding from Packages o Unwinding from Ring-spun Packages o Unwinding from Storage Discs o Application of Balloon Theory to the Shape of the Yarn Inside a Rotor: General Analysis, The Direction of Curvatures of the Yarn Tail, Numerical Solution of Yarn Shape and Tension, Approximate Closed-form Solution of Tb o Appendix 10. Tension Changes along a Threadline: o Introduction o Tension in a Yarn between Two Positively Driven Rollers The Effect of Air Drag on Running-Yarn Tension: Analysis at Higher Speeds, Tension between Two Positively Driven Rollers, Allowing for Air Drag o Tension Changes in a Yarn Moving Over a Stationary Surface: Yarn Passing at Right Angles over a Cylinder, Tensioning Devices 11. Twist Changes along a Threadline: o Introduction o Twist Changes along a Yarn between a Positive-feed Roller and a Positive Twist-insertion Device: Real Twist, False Twist o Dynamic False-twist Changes in a False-twist System o Application to Self-Twist Spinning o Tension and Twist Changes in a Yarn Passing over a Fixed Cylinder at Any Angle o Tension and Twist Changes When a Yarn Passes over a Moving Surface o Application to Rotor Spinning o Application to Texturing by Using Friction Twisting Further Reading Subject Index 95 figures, 10 tables