Warehouse Management (eBook)

Prof. Dr. Michael ten Hompel was born in 1958. He studied Electrical Engineering focusing on technical informatics at the RWTH in Aachen and graduated as PhD from the University of Witten/Herdecke. He started his professional career as scientist at the chair of Transportation and Warehousing of the University of Dortmund and at the Fraunhofer-Institute for Transport Technology and Goods Distribution. From 1989 to 1991 he was director of the Dortmund branch of IGS GmbH & Co. KG in Aachen, a company developing computer systems and networks. In 1988 Prof. ten Hompel founded GamBit GmbH, a company developing software for production and logistics management, today one of Germany’s most successful companies in logistics. In 2000 he resigned from the board to become director of the Fraunhofer-Institute for Material Flow and Logistics (since 2005 managing director) where he is also head of the department "Material Flow Systems". He also holds the chair of Transportation and Warehousing at the University of Dortmund. Dr. Thorsten Schmidt, M.S. holds degrees in mechanical engineering from the University of Dortmund and industrial engineering from the Georgia Institute of Technology. He currently heads the department machinery and systems at the Fraunhofer-Institute for Material Flow and Logistics, focusing on the design and technology of in-house material flow systems.  

Foreword 5
Contents 7
1. Introduction 13
1.1 Requirements 14
1.1.1 Warehousing 14
1.1.2 Characteristics of warehouse systems 16
1.1.3 Optimization of warehouse systems 17
1.2 Warehouse Management 18
1.3 System interfaces and definitions 19
Merchandize management system (MMS) 19
Management information system (MIS) 19
Production planning and control (PPC) 20
Enterprise resource planning (ERP) 20
Material .ow controller (MFC) 20
Warehouse control system (WCS) 20
1.4 Structure and goal of this book 23
2. Management of Warehouse Systems 25
2.1 Logistic frameworks 25
2.1.1 Logistic principles The term logistics 25
2.1.2 Packaging and logistic units 28
2.2 Functions in warehouse systems 32
2.2.1 Goods acceptance and receipt 32
2.2.2 Storage 37
2.2.3 Retrieval / picking 40
2.2.4 Consolidation point 42
2.2.5 Order-picking 42
2.2.6 Packaging department 56
2.2.7 Shipping department 57
2.3 Warehouse management system 58
2.3.1 Warehouse management 58
2.3.2 Reorganization 62
2.3.3 Conveyor management and control systems 62
2.3.4 Data collection, processing and visualization 63
2.3.5 Stocktaking 65
2.4 Basic data and key performance indicators of warehouse systems 68
2.4.1 Basic data Master data 68
2.4.2 Logistic key performance indicators 69
2.5 Special procedures and methods 71
2.5.1 Cross docking 71
2.5.2 Outsourcing of the physical distribution and warehousing processes 73
2.5.3 Application Service Providing 74
3. Fundamentals of an Operational Optimization 75
3.1 Optimization in short 75
3.1.1 Background 75
3.1.2 Classification of the operational optimization 77
3.1.3 Terms and elements of dispatching 79
3.2 Optimization processes in a warehouse 80
3.2.1 Transport optimization 80
3.2.2 Sequencing of picking orders 88
3.2.3 Routing in the warehouse 90
3.2.4 Comprehensive order dispatching 91
3.3 Optimization of solutions 93
3.3.1 General aspects 93
3.3.2 Overview over the optimization procedures 94
3.3.3 Examples of known methods 96
4. Warehousing and Conveying Principles 103
4.1 Warehouse systems 103
4.1.1 Ground store 104
4.1.2 Statical racking systems 106
4.1.3 Dynamical racking system 114
4.1.4 Pre-rack zone 117
4.2 Transport systems 118
4.2.1 Conveyors Roller conveyors 119
4.2.2 Transporters 122
4.3 Sorting and distribution systems 138
4.3.1 Applications 138
4.3.2 The basic structure of sorting systems 140
4.3.3 Distribution technology 144
4.3.4 Control and strategies 147
4.4 Robots in warehouse systems 148
4.4.1 Palletizing robots 148
4.4.2 Order-picking robots 148
5. Automation of the Material Flow 149
5.1 Basics of automation 149
5.1.1 History of the material flow automation 150
5.1.2 Terms and definitions 151
5.1.3 The structure of control systems 152
5.2 Control engineering 156
5.2.1 Classification of controls 156
5.2.2 Programmable logic controllers 159
5.2.3 Computer control 164
5.3 Sensors 165
5.3.1 Sensor classi.cations 165
5.3.2 Mechanically operated sensors 166
5.3.3 Optical sensors 166
5.3.4 Magnetic and inductive sensors 170
5.3.5 Ultrasonic sensors 171
5.4 Actuators 172
5.4.1 The tasks and structures of actuator systems 172
5.4.2 Electrical drives 174
5.4.3 Fluid drives 180
5.5 Interfaces in automation systems 181
5.5.1 Analogous and binary data transmission 182
5.5.2 Digital data transmission 183
5.5.3 Field bus systems 185
6. Automatic Identification 191
6.1 Codes and characters 191
6.1.1 Encoding 192
6.1.2 Encoding examples 192
6.2 1D–Codes 193
6.2.1 Code 2/5 194
6.2.2 Check digit calculation Code 2/5 197
6.2.3 Code 2/5 interleaved 198
6.2.4 Code 128 200
6.2.5 Check digit calculation code 128 203
6.2.6 The character sets of the code 128 204
6.2.7 Mixed character sets in code 128 and their optimization 206
6.2.8 Code sizes, tolerances and reading distances 207
6.3 Printing method and quality 209
6.3.1 Labelling techniques 209
6.3.2 Quality requirements 210
6.3.3 Selection of the printing technique 210
6.4 Semantics in the code: EAN 128 212
6.4.1 Global location numbering (GLN) 213
6.4.2 International article number (EAN) 215
6.4.3 Serial shipping container code (SSCC) 215
6.4.4 Characteristics of the code EAN 128 216
6.5 Scanner technology, devices, interfaces 220
6.5.1 Barcode scanner 220
6.5.2 Handheld scanners 220
6.5.3 Stationary scanners 221
6.6 2D-Codes 222
6.6.1 Stacked barcodes 223
6.6.2 Matrix codes 224
6.7 Radio frequency identi.cation 226
6.7.1 Functioning and technical structure 226
6.7.2 Fields of application 231
6.7.3 Comparison with barcode systems 232
7. Information and Communication Technology 233
7.1 Communication technology 233
7.1.1 Layered architectures 234
7.1.2 Protocols 234
7.1.3 Transmission media 237
7.1.4 Network types and internetworking 239
7.1.5 Network addresses 242
7.1.6 Examples Client- server model 244
7.2 Data management 247
7.2.1 Principles 247
7.2.2 File systems 249
7.2.3 Databases 250
7.2.4 Availability of data 255
7.3 User interface 257
7.3.1 Terminals 258
7.3.2 Functional point of view 259
7.3.3 Access control 260
7.3.4 Internationalization 261
7.3.5 Help systems and help functions 261
7.4 Operating systems 262
7.4.1 Tasks 262
7.4.2 Principles 264
7.5 Programming languages 273
7.5.1 Compilers and interpreters 273
7.5.2 Language concepts 276
7.5.3 Language generations 276
7.6 Basic principles of object-oriented programming 278
7.6.1 Data abstraction 278
7.6.2 Classes and objects 280
7.6.3 Inheritance 281
7.6.4 Unified modelling language 283
7.7 Extensible markup language: XML 283
7.7.1 Key-value-coding 283
7.7.2 The syntax of XML 286
7.7.3 Parsers and processors 287
7.7.4 Variety with style sheets 288
7.8 Safety aspects 289
7.8.1 Secrecy 290
7.8.2 Integrity assurance 292
7.8.3 Authentication 292
7.8.4 Authentication and electronic signature 293
8. Realization of Warehouse Management Systems 295
8.1 Requirement definition 296
8.1.1 As-is analysis 297
8.1.2 Weak-point analysis 298
8.1.3 Development of a target concept 299
8.2 Preparation of the tender documents 299
8.2.1 Definition of the key performance indicators 300
8.2.2 Preparation of the technical specifications 301
8.2.3 Completion of the tender documents 304
8.3 The placement of an order 305
8.3.1 Preselection of providers 305
8.3.2 Comparison of offers 305
8.3.3 O.er presentation 305
8.3.4 Selection of a provider 308
8.4 Implementation 308
8.4.1 Preparation of the technical specifications 308
8.4.2 Realization 312
8.4.3 Project management / Quality assurance 313
8.5 Start-up 313
8.5.1 Test phase 313
8.5.2 Changeover from old to new WMS 314
8.5.3 Training 314
8.6 Acceptance 314
8.6.1 Performance test 315
8.6.2 Failure simulation and emergency strategies 315
8.6.3 Formal acceptance 316
9. Structure of a WMS from the Example of myWMS 319
9.1 Data model 319
9.1.1 Data container of the model 320
9.1.2 Data interrelations 322
9.1.3 Interfaces 325
9.2 Classical implementation of a WMS 325
9.2.1 Functional structure 325
9.2.2 Table structure 327
9.2.3 Securing the logical integrity 330
9.2.4 Generation and query of master data 330
9.3 myWMS 332
9.3.1 The basic structure of myWMS 332
9.3.2 Business objects 335
9.3.3 Kernel concept 336
9.3.4 Runtime environment 338
9.4 Example of a distribution system using myWMS 339
9.4.1 Description of the example 339
9.4.2 Topology structure 345
9.4.3 Plug-In – Routing 347
9.4.4 Communication 348
Abbreviations 353
Bibliography 357
Index 363

5. Automation of the Material Flow ( P. 137)

Automation comprises the independent operation of a technical system in line with high performance and economy. With regard to computer-aided and thus mostly stand-alone functions, warehouse management is also a part of automation, however on a superior business management level (cf. Chapter 2 and 7). Here, above all the strategic and anticipated warehouse and distribution functions are automated.

The automation of the material flow aims at controlling and supervising the operative handling of the material flow. This chapter describes the basics of the material flow automation. Based on a hierarchical classification, we present first the main terms, requirements and tasks. The main elements of an automation technology are the control, sensors and drives to record and influence the material flow processes. The basic structure and functioning of the devices is described in the example of a typical application.

5.1 Basics of automation

Technological and economical aspects affect the technical design and operation of material flow systems and in many cases offer a possibility for automation. Although these requirements di.er from case to case the goals are identical:

– Improved system performance (transshipment rate, shorter order lead times)

– Quality assurance (continuous quality of the products and processes, observance of deadlines)

– Cost savings

– Relief of personnel from uniform, strenuous activities

Whether or not these requirements are met mainly depends on the choice, dimensioning and arrangement of the function areas in the warehouse as well as the used conveyors and storage facilities (cf. Chapter 4). The main task of the automation technology is to ensure the smooth functioning of the single conveyors and storage facilities or their components and to coordinate interlinked systems.

Automation does not always make sense since manual solutions may be more simple or economical. An alternative to the in-house transport of pallets, for example, are the manual transport with a hand pallet truck, a semi-automated transport by stacker or the fully automated transport on driven conveyor belts and automated guided transport systems. Which solution should be preferred depends on the frame conditions set by the overall system and is not studied in detail here.

5.1.1 History of the material flow automation

Modern automation technology was largely affected by inventions in the field of electrical engineering and electronics some of which are listed below (cf. Table 5.1). Obviously, computer-aided data processing has had a considerable in.uence on the development of the modern automation technology, above all the development of microprocessors and the introduction of standardized computer architectures [24].

Almost all digital controls which are currently used in material flow technology are based on these principles. Advanced processors and memories in line with an increasing integration of electronic components set the basis for systems the size of a check card and the performance of a common PC. In addition to central process computers, more and more mobile PC and handheld devices are being used. These are described in more detail in section 5.2.3.