The Art of Ceramic Extrusion (eBook)

Frank Händle has been working as a consultant in the field of extrusion in ceramics since 2015. He is the editor of the Springer book Extrusion in Ceramics, published in 2007.

Acknowledgements 6
Contents 7
1 How to Use This Booklet 12
1.1 For Whom This Booklet Is Written 12
1.2 Some Suggestions for the Use 13
1.3 Conclusions 14
Bibliography 15
2 What Do We Understand by Extrusion in Ceramics? 16
2.1 Shaping Methods in the Ceramics Industry 16
2.2 What Is Extrusion? 18
2.3 Criteria for Extrusion 19
2.4 Feeding Systems 22
2.5 Auger and Barrel 23
2.5.1 Auger 23
2.5.2 Barrel 24
2.6 De-airing 24
2.7 Extruded Ceramic Products 25
2.8 Conclusions 25
Bibliography 26
3 Ceramic Materials—The Malice of the Object 27
3.1 Definition of Ceramics 27
3.2 Classification of Ceramic Materials 27
3.3 Classification of Ceramics According to Applications 28
3.4 The Main Properties of Ceramic Bodies for Extrusion 28
3.4.1 Plasticity 30
3.4.2 Yield Point, Viscosity and What Mr. Bingham Has to Say 30
3.4.3 Homogeneity 32
3.4.4 Grain Size Distribution 32
3.4.5 Wall Friction 33
3.5 Conclusions 33
Bibliography 34
4 A Little Bit of Theory 35
4.1 What This Chapter Is About 35
4.2 Basic Terminology 35
4.3 Scenarios of Pressure Build-up in the Extruder 37
4.3.1 Scenario 1: The Notorious “Backflow” 38
4.3.2 Scenarios 2 and 3—“Backflow” Again, but for Other Reasons 39
4.4 The Benbow–Bridgwater Equation 40
4.5 How to Calculate the Output of an Extruder 41
4.6 Conclusions 43
Bibliography 43
5 How to Determine an Extruder and Which Data Do We Need? 44
5.1 The Decision Procedure and the Database 44
5.2 The Decision Model 45
5.3 About the Sense and Nonsense of Questionnaires 46
5.4 Conclusions 48
Bibliography 49
6 Plasticity or the Great Unknown 50
6.1 What Does Plasticity Mean in Ceramics? 50
6.2 The Two Plasticities 50
6.3 How Do We Measure the Two Plasticities? 51
6.4 Factors Determining Plasticity of a Ceramic Body 53
6.5 Two Methods to Measure the Development of Plasticity 53
6.5.1 Good-Natured and Nasty Ceramic Bodies-the Consistency Curve 54
6.5.2 Kneading Curve 55
6.6 Plasticity or Consistency or Extrudability? 56
6.7 Conclusions 57
Bibliography 57
7 Mixing and Kneading 58
7.1 Short Introduction 58
7.2 Mixing 58
7.3 Kneading 59
7.4 Macro-mixing and Micro-mixing 61
7.5 Buffer Systems or Dosing Strainers? 61
7.6 The Ceramic Body as Dispersed Material System 62
7.7 Conclusions 63
Bibliography 64
8 Extrusion as a System 65
8.1 What Do We Understand by a System? 65
8.2 Components of a System 66
8.3 Consequences 67
8.4 Conclusions 69
Bibliography 70
9 Laminations and Chaos 71
9.1 What Do We Understand by Laminations? 71
9.2 Formation of Laminations 72
9.2.1 The Pioneering Studies by BCRA 72
9.2.2 Where Are Laminations Generated in Extrusion? 73
9.3 Types of Laminations 74
9.3.1 Flow Laminations 74
9.3.2 Cutting Laminations 76
9.3.3 Rotational Laminations 77
9.3.4 Hub Laminations 77
9.3.5 Laminations Caused by Insufficient De-airing 78
9.3.6 Combined Laminations 78
9.4 What Can Be Done? 79
9.5 Conclusions 79
Bibliography 79
10 About the Brave New World of Sensors and Control 80
10.1 Introduction 80
10.2 The Mechatronic Model 80
10.3 Why There Is a Compelling Necessity for Better Measuring Systems for Ceramic Extrusion? 82
10.4 What Are the Most Important Operating Data for Extrusion? 82
10.5 Aggregated Measured Values/Operating Data 84
10.6 Conclusions 85
Bibliography 85
11 Ancillary Equipment and Accessories 86
11.1 The Most Important Accessories for the Extrusion Unit 86
11.2 Foundation, Base Frame and Supporting Structure 86
11.3 Control 87
11.4 Cooling/Chilling of Augers and Barrels 88
11.4.1 Why and When Must an Extruder Be Cooled? 88
11.4.2 Selection of the Cooling Unit 88
11.4.3 The Major Operating Data for the Cooling System 89
11.4.4 Also to Be Noted 90
11.5 Vacuum Pump and Vacuum Monitoring 90
11.5.1 Definition of the Vacuum Pump 90
11.5.2 How to Measure the Level of Vacuum Correctly 91
11.5.3 Types of Vacuum Pumps 91
11.5.4 Regulation and Measurement of the Vacuum 93
11.5.5 Checking and Testing the Vacuum 93
11.6 Hydraulic and Pneumatic Equipment 94
11.7 Screen and Die Changers 94
11.8 Infrastructure 94
11.9 Conclusions 95
Bibliography 96
12 Pressure Heads and Dies 97
12.1 What Matters 97
12.2 Typical Pressure Head/Die Combinations 98
12.2.1 Example 1: Pressure Head/Die Combination to Produce Large Brick Blocks 98
12.2.2 Example 2: Pressure Head/Die Combination to Produce Stiff-Extruded Face Bricks 99
12.2.3 Example 3: Typical Pressure Head/Die Combination to Produce Honeycombs 100
12.3 A Look Over the Fence 101
12.4 Conclusions 102
Bibliography 103
13 Extrusion Problems and How to Solve Them 104
13.1 A Bit of Help for Self-help 104
13.2 Conclusions 108
Bibliography 108
14 Pelletizing by Extrusion 109
14.1 What Do We Understand by Pelletizing? 109
14.2 Pelletizing by Extrusion 109
14.3 Plasticity as a Prerequisite for Pelletizing 111
14.4 Pellet Geometry 112
14.5 Essential Features of a Pellet Extruder 112
14.6 Dies and Matrix Plate 113
14.7 Matrix Plate Changer 114
14.8 Other Pelletizing Methods 115
14.9 Conclusions 116
Bibliography 116
15 Wear, Tear and No End 117
15.1 Wear—A Real Challenge 117
15.2 Types of Wear 117
15.3 Summary of the Most Important Wear Solutions 119
15.4 Roughness of Auger Surfaces 121
15.5 “Where There Is No Friction There Is No Wear” 122
15.6 Function of the Barrel in Extrusion of Ceramic Materials 123
15.7 Conclusions 124
Bibliography 124
16 The Ceramic Production Laboratory 125
16.1 What Are the Reasons for Having a Production Laboratory? 125
16.2 The Types of Production Laboratories 125
16.3 Frequency of Sample Testing 126
16.3.1 When and How Often? 126
16.3.2 The Worst Case 127
16.4 The Subject of Random Samples 128
16.5 A Short Real-Life Story 128
16.6 Methods and Instruments 129
16.7 Conclusions 132
Bibliography 133
17 Does that Exist—The Optimal Extruder? 134
17.1 A Sad Story 134
17.2 Questions and Criteria 134
17.3 Optimal Extruder?=?Optimal Extrusion? 136
17.4 Conclusions 136
Bibliography 137
18 A Look-Ahead 138
18.1 Predictions, Strategies and Wishes 138
18.2 Gaps and Blind Spots 140
18.2.1 The Know-How Gap 140
18.2.2 The Wear Protection Gap 140
18.2.3 The Sensor Gap 141
18.3 En Route to the “Smart Extrusion Concept” (SEC) 141
Bibliography 143