Contents
Preface ix
Acknowledgement xi
1. Quality management 1
1.1 What is quality? 1
1.2 Quality as input–output system 1
1.3 Quality feedback cycle 2
1.4 Seven tools of quality 3
1.5 Quality management in spinning industry 10
1.6 Organization of quality control 12
1.7 References 18
2. Application of statistics in textiles 20
2.1 Introduction 20
2.2 Measures of central tendency 22
2.3 Measures of variation 25
2.4 Distributions 27
2.5 Comparison of two results 32
2.6 Quality control within the spinning mill 36
2.7 References 40
3. Cotton fibre selection and bale management system 42
3.1 Introduction 42
3.2 Cotton 44
3.3 HVI 46
3.4 Spinning Consistency Index (SCI) 50
3.5 Cotton fibre engineering 52
3.6 References 67
4. Control of wastes in spinning 69
4.1 Yarn realization 69
4.2 Control of blow room waste 81
4.3 Control of card waste 96
4.4 Control of comber waste 106
4.5 Contamination removal techniques 120
4.6 References 138
5. Control of neps and fibre rupture 141
5.1 Introduction 141
5.2 Guideline values for neps in bale as per Uster 143
5.3 Evaluation of machine efficiency 144
5.4 Control of nep generation and fibre rupture in blow room 146
5.5 Control of neps and fibre rupture in card 152
5.6 Control of neps and short fibre content in comber 161
5.7 Influence of modern developments on nep removal 165
5.8 References 174
6. Control of count, strength and its variation 175
6.1 Introduction 175
6.2 Control of count 175
6.3 Control of count variation 178
6.4 Between-bobbin count variation 188
6.5 Control of variability of lea strength 190
6.6 Control of yarn elongation 192
6.7 References 195
7. Yarn evenness and imperfection 196
7.1 Introduction 196
7.2 Categories of yarn faults 197
7.3 Unevenness (Um%) 199
7.4 Mass CV (Coefficient of Variation Cvm%) 200
7.5 Yarn imperfections 216
7.6 References 224
8. Short-term irregularity 226
8.1 Autolevelling 226
8.2 Autolevellers in carding 230
8.3 Autolevellers in draw frame 231
8.4 Advantages of high performance leveling 241
8.5 Control of yarn evenness (U%) 241
8.6 References 251
9. Interpretation and analysis of diagram, spectrogram and V-L curve 253
9.1 Introduction 253
9.2 Measuring principle of mass evenness 253
9.3 Normal diagram 254
9.4 Spectrogram 257
9.5 Variance-length curve 295
9.6 Deviation rate 301
9.7 Histogram of mass variations 304
9.8 References 305
10. Control of yarn hairiness in spun yarns 307
10.1 Introduction 307
10.2 Parameters influencing the generation of yarn hairiness 309
10.3 Influence of ring frame parameters on yarn hairiness 311
10.4 Influence of preparatory process on yarn hairiness 318
10.5 Effect of Post Spinning Operations on hairiness 319
10.6 Control of hairiness of ring spun yarns 320
10.7 Influence of hairiness on subsequent processing 322
10.8 References 322
11. Yarn faults 325
11.1 Introduction 325
11.2 Distinction between frequent and seldom-occurring yarn faults 328
11.3 Causes for seldom-occurring yarn faults 329
11.4 Standard settings in classimat 330
11.5 Analysis of classimat faults 331
11.6 Common yarn faults in ring yarn 334
11.7 References 341
12. Productivity of a spinning mill 343
12.1 Introduction 343
12.2 Productivity indices 344
12.3 Control of end-breakage rate in ring spinning 346
12.4 Control of end breaks in ring spinning 350
12.5 Effect of climatic conditions on spinning process 354
12.6 References 355
13. Yarn quality requirements for high-speed machines 356
13.1 Yarn quality requirements for hosiery yarns 356
13.2 Yarn quality requirements for export 361
13.3 Yarn quality characteristics of sewing threads 361
13.4 Yarn quality requirements for shuttleless weaving 362
13.5 Measures to produce better yarns 365
13.6 References 366
Annexure: Basic conversion charts 367
Index 401
Preface
Changes are taking place very fast all over the world in all fields, such as technological developments, the living styles, social environment, and the perception of people. In this changing scenario, rising expectations of the customer and open market economics are forcing businesses to compete with each other. Therefore, basic quality of the product at competitive market price is a key factor. The same holds good for textile industry also which is one of the oldest and has a number of players all over the world. Today textile industry is facing higher competition in the globalized market than ever before. When it comes to textile, spinning is the key process, which has been given vital importance because many of the fabric properties, working of weaving machines and weaving preparatory machines are dependent on yarn quality. The overall level of quality is increasing constantly. Due to steadily growing production capacities, the quality consistency must be improved.
Keeping this in mind, process control and yarn quality in spinning outlines the concepts of raw material selection, control of various process parameters to optimise the process conditions, and analysis and interpretation of various types of test reports to find out the source of fault. The book is divided into thirteen chapters, each discusses some specific area in process and quality control. This book takes a close look at the advancing technology in manufacturing and process and product quality control. It provides a basic overview of the subject and also presents applications of this technology for practicing engineers. It also includes real-time case studies involving typical problems that arise in spinning processes and strategies used to contain them. This book finds worthy to broad range of readers, including students, researchers, industrialists and academicians, as well as professionals in the spinning industry.
Chapter 1 presents the various definitions and dimensions of quality and their significance on process and quality control. Chapter 2 discusses the significance of statistical quality control in textile industry. Chapter 3 converses about the significance of raw material selection and bale management in a spinning industry for the production of consistent yarn quality. Chapter 4 presents the various control points and remedial measures in each process for the control of waste to improve the yarn realization in spinning. The effect of contamination on final yarn quality and various techniques of contamination removal during spinning processes have also been discussed in detail. Chapter 5 provides insight into the types of neps and their measurement and control in blow room, carding and comber processes. Chapter 6 deals with the control of yarn count and strength and its variation to produce the uniform and consistent yarn quality. The influence of material and process parameters in each stage of process on count variation and sampling of materials for testing the count variation have also been discussed. Chapter 7 discusses the basic category of yarn faults with their basic characteristics and their usefulness on evaluation of yarn quality. Chapter 8 provides the concept of autolevelling and the influence of various process and machine parameters in each processing stages on yarn evenness. Chapter 9 provides an insight about the various quality control graphical representations from the evenness testers such as normal diagram, spectrogram and V-L curves. Chapter 10 presents the influence of material and process parameters on yarn hairiness and its influence on fabric appearance.
Chapter 11 provides causes and remedial measures of various types of yarn faults created by the raw material, preparatory process and ring frame. Chapter 12 deals with the various productivity indices and factors influencing the productivity of the ring spinning. The yarn quality requirements for hosiery, shuttless weaving and for export are discussed in Chapter 13.