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Introduction 1 1.1 The Role of Grinding in Manufacture Origins of Grinding What Is Grinding? A Strategic Process I Quality and Speed 2 Machining Hard Materials 2 Accuracy 3 Surface Texture 3 Surface Quality 3 Speed of Production 3 Cost 4 The Value Added Chain 4 Reducing the Number of Operations 4 1.2 Basic Grinding Processes 5 1.3 Specification of Elements 7 Basic Elements 7 System Elements 8 Element Characteristics 8 Grinding Machine 9 Grinding Fluid 9 Atmosphere 9 1.4 The Book and Its Contents 10 2 Basic Material Removal 15 2.1 The Removal Process 15 2.2 Depth of Material Removed 17 The Stiffness Factor K 19 Size Error 20 Barrelling 21 2.3 Equivalent Chip Thickness 21 2.4 Material Removal Rate 22 2.5 Specific Grinding Energy 23 2.6 Forces and Power 25 Grinding Power 25 Grinding Force Ratio 26 Typical Forces 26 Wet Grinding 29 Effect of Abrasive Type 29 2.7 Maimizing Removal Rate 30 Process Limits 30 Limit Charts 31 References 33 3 Grinding Wheel Developments 35 3.1 Introduction 35 3.2 Abrasives 35 Superabrasives 37 Diamond 37 Cubic Boron Nitride 38 Conventional Abrasives 38 Silicon Carbide 38 Aluminium Oxide 39 Sintered Alumina 40 3.3 Wheel Bonds 41 Organic Bonds 41 Vitrified Bonds 42 Metal Bonds 43 3.4 Grinding Wheels 43 3.5 Wheel Specification 44 Standard Marking System Conventional 45 System for Superabrasive Wheels 45 Grain Size 45 Grade 47 Structure Number 48 Porosity 48 Concentration 49 3.6 Wheel Design and Application 49 Safety 49 Wheel Mounting 49 Balancing 50 3.7 High Speed Wheels 51 Unbalanced Stresses 51 Balanced Stresses 51 Practical Considerations for Design of High Speed Wheels 54 A Solid Wheel 54 Central Reinforcement 54 A Tapered Wheel 55 Bonding to a Metal Hub 55 Bonded Segments 55 Metal Bond 55 Dressable Metal Bond 56 3.8 Wheel Elasticity and Vibrations 56 References 58 4 Grinding Wheel Dressing 59 4.1 Introduction 59 4.2 Stationary Dressing Tools 59 Multi Point Diamond Tools 60 Form Dressing Tools 60 Single Point Diamond Tools 60 The Dressing Process 60 Overlap Ratio 61 Dressing Tool Sharpness 61 Coarse and Fine Dressing 62 4.3 Rotary Dressing Tools 63 Dressing Roll Speed Ratio 63 Dressing Vibrations 65 Grinding Wheel Dressing Speed 66 4.4 Grinding Performance 66 Dressing Traverse Rate 66 Coarse, Medium, and Fine Dressing 67 Dressing Tool Wear 68 4.5 Touch Dressing for CBN Wheels 69 Purpose of Touch Dressing 69 Grinding Performance 69 Touch dressing Equipment 71 Acoustic Emission (AE)& Contact Sensing 72 Wheel Loading 73 4.6 Continuous Dressing 74 4.7 Electrolytic In process Dressing (ELID) 75 References 78 5 Wheel Contact Effects 79 5.1 The Abrasive Surface 79 Grain Size and Grain Sharpness 79 Shape Conformity 79 Abrasive Structure 79 Grain Spacing and Distribution 80 Wheel Flexibility 82 5.2 Grain Wear 82 Rubbing Wear 82 Bond Fracture 83 Grain Micro Fracture 83 Grain Macro Fracture 83 Wheel Loading 83 Preferred Wheel Wear 84 Wear Measurement 84 G Ratio 84 Wear Flats 85 Re sharpening 86 5.3 Wheel Workpiece Conformity 87 Equivalent Diameter 87 5.4 Contact Length 89 Geometric Contact Length 89 Kinematic Contact Length 91 Deflected Contact Length 91 Total Contact Length 92 Contact Length Ratio 93 References 93 6 High Speed Grinding 95 6.1 Introduction 95 6.2 Trends in High Speed Grinding 95 Quality, Productivity, and& Cost 95 Better Removal Rate Better Accuracy& 95 6.3 High Speed Domains 97 6.4 High Efficiency Grinding 97 Early Development 97 Machine Requirements 98 Emulsion or Neat Oil 98 Speed Ratio 99 6.5 Creep Feed Grinding 99 6.6 High Efficiency Deep Grinding (HEDG) 100 HEDG Development 100 Drill Flute Grinding 101 Crankshaft Grinding 101 Chip Thickness 101 Specific Energy 102 Viper Grinding 102 Temperature Analysis 102 6.7 High Work Speed Grinding 103 Cylindrical Grinding 103 Speed Stroke Grinding 103 References 103 7 Avoiding Thermal Damage 105 7.1 Introduction 105 Types of Thermal Damage 105 Damage Avoidance 105 7.2 The Iron Carbon Diagram 106 Explaining Thermal Damage 106 7.3 Bum and Temper Damage 106 Severe Oxidising Bum 106 Temper Damage 107 7.4 Re hardening Damage 108 Surface Cracks 109 7.5 Residual Stresses 109 7.6 Grind Hardening 7.7 Process Monitoring Barkhausen Noise Sensors Monitoring Power 112 Process Control 112 References 112 8 Application of Fluids 113 8.1 Introduction 113 Types of Grinding Fluid 113 Functions of a Grinding Fluid 113 Contact Area Cooling 113 Reduction of Wheel Wear 113 Bulk Cooling 114 Swarf Flushing 115 Minimum Quantity Lubrication (MQL) 115 Safe Use and Disposal of Fluids 115 Alternative Lubrication Possibilities 116 Total Life Cycle Costs 116 Oil versus Water Based Fluids 116 Fluid Properties 116 Dry Grinding 117 8.2 Water Based Fluids 117 Re circulating Systems 117 Fluid Treatment 117 Fluid Compositions 118 8.3 Neat Oils 118 Mineral Oils 120 Synthetic Oils 120 8.4 MQL and Gas Jet Cooling 120 MQL with Oil 120 Mist Cooling 121 Cryogenic Cooling 121 Ice Air Jet Blasting 121 8.5 Pumping System 121 Basic Elements 122 Separation 122 Heat Exchanger 122 Wheel Absorption of Fluid 123 Supply Flow Rate and Pressure 123 |
8.6 Fluid Delivery 123 Hydrodynamic Effects and Size Control 123 Roughing and Finishing Requirements 124 Air Barrier 124 Highly Porous Wheels 125 Sealing the Wheel 125 Pore Feeding 125 Use of an Air Scraper 125 Nozzle Position and Fluid Speed 126 Nozzle Arrangements 126 Auxiliary Nozzles 127 Positioning the Jet 127 Coherence 128 Webster Nozzle 128 Coherent Length 129 Nozzle Comparisons 129 Shoe Nozzle 130 Nip 130 8.7 Nozzle Design Calculations 131 Turbulence 131 Round Orifice Nozzle 131 Round Pipe Nozzle Transitional Flow 133 Rectangular Nozzle 133 8.8 Nozzle Flow Rate Requirements 134 Useful Flow Rate 135 Nozzle Flow Rate 135 Achievable Useful Flow Rate 135 Measured Useful Flow Rate 138 Bulk Cooling 140 8.9 Power Required to Accelerate the Fluid 141 Spindle Power 141 Total Power 141 References 143 9 Cost Reduction 145 9.1 Introduction 145 Output, Quality, and Cost 145 Total Life Cycle Costs 145 Cost Variables 145 Overhead Costs 146 Wheel, Machine, and Labour Costs 146 9.2 Analysis of Cost per Part 147 Cost Elements 147 Total Cycle Time 147 Grinding Cycle Time 147 Dressing Cycle Time 148 Dressing Frequency 149 Number of Parts per Wheel 149 Wheel Cost per Part 150 Labour Cost/Part 150 Machine Cost/Part 151 Total Variable Cost/Part 152 9.3 Cost Reduction Trials 152 Basic Trials 153 Direct Effects 154 Selection of Best Conditions 155 Confirmation Trials 156 9.4 Cost Comparisons for AISI 52 100 156 Grinding Wheels 157 Best Conditions 157 Conventional Speed Alumina and SG Wheels 158 Conventional Speed CBN Wheel 158 High Speed B91 CBN Wheel 158 Cost Comparison 158 Re dress Life 159 9.5 Cost Comparisons for Inconel 718 159 Grinding Wheels 159 Best Conditions 160 Conventional Speed A1203Wheel 160 Conventional Speed Vitrified B 151 CBN Wheel 160 High Speed B 151 CBN Wheel 160 Re dress Life and Cost Comparison 160 References 161 10 Grinding Machine Developments 163 10.1 Machine Requirements 163 Stiffness 163 Accuracy 163 Thermal Deflections 163 Wear 164 10.2 Grinding Machine Elements 164 10.3 Machine Stiffness and Compliances 164 Definition of Static Stiffness 164 Damping 167 C Frame and U Frame Structures 167 Slide Ways and Bearing Deflections 167 Compliances and the Force Loop 168 Improvement of Grinding Performance 170 Improvement during Spark Out Time 170 10.4 Design Principles for Machine Layout 171 10.5 Spindle Bearings and Wheel Heads 174 Spindle Elements 174 Spindle Roundness 174 Spindle Types 174 10.6 Plain Hydrodynamic Spindle Bearings 174 10.7 Rolling Bearings 175 10.8 Hydrostatic and Hybrid Bearings 176 Advantages 176 Basic Design 177 Restrictors 178 Maximum Load 178 Flow rate 179 Average Oil Film Stiffness 179 Concentric Stiffness 180 Pumping Power 180 Friction Power 180 Power Ratio 181 Temperature Rise 182 10.9 Air Bearing Spindles 182 Features 182 Basic Design 183 Restrictors 183 Air Journal Bearing Load 184 10.10 Machine Base 184 10.11 Column Deflections and Thermal Effects 185 Bending Deflections 185 Thermal Deflections 186 10.12 Joints, Slide Ways, and Feed Drives 187 Feed Drive Elements 187 Positioning Accuracy 187 Movement Directions 188 Joint Deflections 190 Slide Ways 191 Plain Bearing Slide Ways 191 Rolling Element Slide Ways 192 Hydrostatic Slide Ways 192 Air Bearing Slide Ways 193 Feed Drive Mechanisms 193 Feed Drive Controls 194 10.13 Trends in Grinding Machine Development 195 High Wheel Speed Grinders 195 Deep Forrn Grinders 195 Speed Stroke Grinders 196 Multi Part Grinders 196 Multi Tool Grinders 197 Flexible Multi Part Grinding 197 10.14 Ultra Precision Grinders 198 Applications 198 Basic Principles 198 Ultra Precision Centreless Grinder (Rowe 1979; Spraggett 1979; Rowe et al. 1987) 199 Ultra Precision Surface and Centreless Grinders (Yoshioka et al. 1985) 199 Ultra Precision Grinding Using Ultra Fine Abrasive Pellets (Ikeno et al. 1990) 202 Ultra Precision Grinding with ELID (Ohmori and Nakagawa 1990) 203 Mass Production Double Sided Face Grinder (KMT Precision Grinding AB, 1998) 203 Magnetic Fluid Grinding of Ceramic Balls (Childs et al. 1994) 204 Ultra Precision Grinding Machine: "Nano Centre" (McKeown ;et al. 1990) 204 Magnetic Memory Disk Combination Grinder (Cranfield Precision Engineering 1993) 205 Ultrasonic Assisted Grinding (Uhlmann 1998; Uhlmann et al. 2000) 205 Precision Big OptiX (BoXTm) Grinding and Measuring Machine (Shore et al. 2005) 207 References 208 11 Process Control 211 11.1 Process Variability 211 Variations due to Wheel Wear 211 Limits and Tolerances 212 Size Variations due to Dresser Wear 213 Process Stabilisation 214 In Process Gauging 214 11.2 Classes of Machine Control 216 Manual Control 217 Switching Control 217 Computer Numerical Control (CNC) 218 Intelligent Control 218 11.3 Intelligent Control of Grinding 220 Adaptive Strategy 221 Adaptive Feed Rate Control 221 Adaptive Dwell Control 222 Role of Time Constant 223 Time Constant during In Feed 224 Time Constant during Dwell 225 Control of Plunge Grinding 226 11.4 Knowledge Based Intelligent Control Systems 227 General Framework for Intelligent Control 228 Systems and Intelligent Databases 228 The CNC 229 Monitoring and Adaptive Control Optimisation (ACO) Modules 229 Temperature Sensing 230 Gap Elimination 230 Touch Dressing 230 Power Sensing 231 Operator Inputs 231 Thermal Damage 231 References 231 12 Vibration Problem Solving 233 12.1 Introduction 233 Impulsive Vibrations 233 Forced Vibrations 234 Self Excited Vibrations 234 12.2 Dynamic Relationships for Grinding 236 Block Diagram 236 Basic Equations 237 Basic Solutions 239 Free Vibration 239 Forced Vibration 239 Transfer Functions 239 12.3 Contact Length Filtering 240 12.4 Machine Stiffness Characteristics 242 Excitation Tests 242 Light Running Tests 244 12.5 Stiffness,Damping,Resonance 245 12.6 Chatter Conditions 247 Introduction 247 Graphical Stability Determination 248 Using Measured Frequency Responses 249 Reducing Overlap in Traverse Grinding 250 Reducing Wheel Contact Stiffness 251 Adding Flexibility to System 252 Varying Work Speed or Wheel Speed 253 Adding Vibration Damping 254 References 254 |
13 Centerless Grinding 257 13.1 Introduction 257 Application 257 Research by the Author 257 Research by Other Authors 258 13.2 Centreless Grinding Processes 258 External Centreless Grinding 258 Internal Centreless Grinding 260 External Shoe Grinding 260 Internal Shoe Grinding 261 13.3 Set Up Geometry/Removal Param 261 Contact Geometry 261 Work Plate Angle 261 Work Height 262 Tangent Angle 262 Experimental Rounding Investigation 263 Removal Parameters for Plunge Grinding 264 13.4 Work Feed 264 Plunge Feed 264 Through Feed 265 Tilt Angle 266 13.5 Wheel Dressing 266 Grinding Wheel Dressing 266 Control Wheel Dressing 267 Position A 267 Position B 268 Control Wheel Run Out 268 13.6 Machine Design, Roundness Errors, & Productivity 269 Machine Design 269 Work Speed and In Feed Rate 270 13.7 Convenient Waviness 270 Work Plate Corrective Action 271 Control Wheel Corrective Action 272 13.8 Simulation of the Rounding Action 272 Basic Simulation Equation 273 Interference and Loss of& Contact& Constraints 274 Simulation Results 276 13.9 The Shape Formation System 277 13.10 Stability of the Rounding Process 278 Stability of a Closed Loop System 278 Geometric Instability 279 Geometric Stability Parameter "A" 280 Integer Wave Stability 282 Regions of Instability 282 13.11 Effect of Deflections 284 Static Deflections 284 Dynamic Deflections 285 13.12 Avoiding Dynamic Problems 286 14 Material Removal byGrains 291 14.2 Equivalent Chip Thickness 292 Empirical Relationships for Grinding Data 293 Limitations of heq 293 14.3 Cutting Edge Contacts 294 Random Cutting Action 294 Representation by Poisson Distribution 294 Cutting Edge Density 296 Effect of Wear 296 Cutting Edge Shape 297 14.4 Cutting Edge Contact Times 298 14.5 The "Uncut Chip" 300 Effects of the Uncut Chip Dimensions 300 Use of Kinematic Models 300 Basic Kinematic Model 300 Basic Chip Shape Models 301 14.6 Chip Length 302 14.7 Chip Volume Based on Removal Rate 302 14.8 Chip Cross Section Area 303 14.9 Chip Thickness 304 General Expression for Chip Thickness 304 Chip Width to Chip Thickness Ratio Triangular Chip 305 Triangular Chip Thickness 305 Spherical/Round Chip Thickness 306 Comparison of Mean Chip Thickness Values 307 Maximum Chip Thickness 307 Chip Thickness Conclusions 307 Grain Density Variations 308 14.10 Surface Roughness 309 14.11 Appendix: Maximum Chip Thickness Derivation from Geometry 312 References 314 15 Real Contact 315 15.1 Real and Apparent Contact Area 315 15.2 Real Contact Length 316 15.3 Smooth Wheel Analysis 320 15.4 Rough Wheel Analysis 321 15.5 Calibration of the Roughness Factor R, 323 Comparison with Verkerk 323 Defining Contact Length Empirically 324 Qi Measurements 325 Contact Length Ratio 326 References 327 16 Specific Energy 329 16.1 Introduction 329 16.2 The Size Effect 329 Measured Specific Energy 329 Relationship to heq 329 Physical Reasons 330 16.3 Threshold Force Effect 331 16.4 Surface Area Effects 331 Surface Area Created 331 Chip Volume and Surface Area 331 Specific Energy and Surface Area 331 Depth of Cut and Surface Area 332 Grain Density and Surface Area 332 Work Speed and Surface Area 332 Conclusion Chip Thickness and Specific Energy 333 16.5 Grain Shape and Sharpness Effects 333 Quantifying Sharpness 333 Indentation Model 334 Wear and Dressing Effects on Grain Shape 335 16.6 Rubbing, Ploughing, and Cutting 335 3 Domains of Abrasive Contact 335 Rubbing 335 Ploughing 335 Cutting 335 Sub Threshold Condition 335 3 Energy Components 336 Sliding or Rubbing Energy 336 Chip Formation Energy 337 Minimum Energy Asymptote 337 Ploughing Energy 338 References 339 17 Mechanics of Abrasion 341 17.1 Introduction 341 17.2 Primary, Secondary, Tertiary Shear Zones 341 Primary Shear 341 Shear Strain Rates 342 Transition from Compressive to Tensile 342 Redundant Energy 342 Blunt Cutting Action 342 Minimum Energy Principle 343 17.3. Rubbing Contact 343 Basic Adhesion 343 Interface Friction 344 Junction Growth 345 Three Dimensional Stresses with Junction Growth 345 17.4 Ploughing Contact 347 Basic Rabinowicz Model 347 Modified Rabinowicz Model 348 Cone and Sphere Model 349 17.5 Indentation Analysis 350 Slip Line Field Analysis 350 Pare Indentation 350 Friction Angle 350 17.6 Indentation with Sliding 351 17.7 Basic Challen and Oxley Models 351 Wave Rubbing 352 Wave Wear 354 Chip Formation 354 17.8 Oblique Cutting 356 17.9 Wear 357 Tribo Chemical Conditions 357 Adhesive Wear 358 Wear Life Cycle 359 Real Contact Length 359 Application of Archard's Law 360 Determination of K 360 Yield Mode 360 Fatigue 360 Abrasive Wear 361 Oxidative Wear 361 Corrosion 361 Thermal Wear 362 Chemical Wear 362 Grinding Fluid 362 References 362 18 Temperatures in Grinding 365 18.1 Introduction 365 18.2 Background 365 Development of Temperature Analysis 365 A Moving Heat Source 365 Four Heat Flows 365 Workpiece Conduction 366 Fluid Convection 366 Chip Energy 367 Heat Partitioning 367 Work Partition Ratio R, 367 Work Wheel Fraction 367 Heat to the Wheel 367 Wheel Contact Analysis 368 Grain Contact Analysis 368 Real Contact Length 368 Total Grinding Energy 368 Energy Monitoring 369 Damage Temperatures 369 Grain Thermal Properties 369 Workpiece Thermal Properties 369 18.3 Heat Input and Heat Dissipation 370 Heat Input 370 Heat Dissipation 371 Flash Heating 371 Grain Heating 371 Background Heating 372 18.4 Workpiece Surface Temperatures 372 Workpiece Temperature Rise 372 Heat Partitioning 373 Heat Flux Definition 374 Chip Flux 374 Work Wheel Fraction 375 Fluid Convection 376 Predictions of Fluid Convection Coefficient h; 377 Peclet Number and Diffusivity 378 Contact Angle 379 C Factors for Maximum Temperatures 379 Contact Surface Temperatures and Finished Surface Temperatures 380 18.5 Workpiece Sub Surface Temperatures 381 Accurate Two Dimensional Method 381 Approximate One Dimensional Method 382 One Dimensional Solution Technique 383 Linearised Curve Fits and Averaging 383 18.6 Temperature Measurement 384 Grain Temperatures 384 Background Temperature Methods 384 Surface Temperature Thermocouples 384 Dry Grinding 385 Wet Grinding 386 18.7 Measured Temperatures 387 Effect of Abrasives 387 Effect of Depth of Cut 388 Effect of Grain Sharpness 388 Effect of Grinding Fluid 389 Shallow Cut or Deep Cut? 390 High Removal Rate Grinding 390 Wheel Wear 392 Work Material 392 18.8 Appendix A: General Solution for Grinding Temperatures 392 18.9 Appendix B: Derivation of Work Wheel Fraction 395 Analysis of Conduction into the Workpiece 395 Analysis of Conduction into the Grain h9 396 References 397 Index 399 |