This thesis presents a newly developed manufacturing method, based on cyber-physically enhanced hybrid machining, regarding an optical bench (OB) made of Ti6Al4V alloy for the Advanced Telescope for High-ENergy Astrophysics (ATHENA). The method includes sophisticated hybrid laser metal deposition equipment and state-of-the-art cryogenic machining hardware. The derived strategy combines localized energy input, preheating, heat treatment, intermediate stress relief and machining. This results in a complex thermal history and remaining residual stresses, representing a considerable challenge for final precision machining. The method targets first time right machining based on iterative machining, process data-based tool path correction and spatially resolved root cause research based on process data modeling.:II. Table of Contents
I. Acknowledgement ............................................................ III
II. Table of Contents ................................................................. I
1. Introduction ........................................................................ 1
1.1 Foreword .................................................................................... 1
1.2 Research Subject Lot Size One ....................................................... 2
1.2.1 Historical Perspective ................................................................. 2
1.2.2 Going Full Cycle ......................................................................... 3
2. State of the Art in Titanium Processing ............................... 4
2.1 Conventional Processing................................................................ 4
2.2 Additive Manufacturing ................................................................. 5
2.2.1 Introduction .............................................................................. 5
2.2.2 Powder Bed Fusion ..................................................................... 6
2.2.3 Direct Energy Deposition ............................................................. 8
3. Derivation of a Flexible Hybrid Manufacturing System ...... 11
3.1 The ATHENA OB – a Large Structural Space Component ..................11
3.2 Material Constraints ....................................................................12
3.3 Solidification and Microstructural Content .......................................17
3.4 Residual Stresses and Intrinsic Heat Treatment ..............................22
3.4.1 Transient Temperature Gradients ................................................22
3.4.2 Residual Stresses and Degree of Fixity ........................................24
3.4.3 In-situ Stress Relief and Plastic Deformation ................................28
3.4.4 In-situ Martensite Decomposition and Thermal Trade-off ...............30
3.5 Melt Pool Considerations in Laser Metal Deposition ..........................36
3.6 Concept of Flexible Hybrid Manufacturing Cell .................................43
3.7 Process and Equipment Review by ESA ..........................................45
4. Realization of a Flexible Manufacturing Cell ...................... 45
4.1 Additive Processing with Hybrid Laser Metal Deposition ....................45
4.1.1 Principle Hardware ....................................................................45
4.2 Novel Local Shielding Solution ......................................................47
4.2.1 Melt Pool Observation towards Process Data Model ........................51
4.2.2 Energy Source Coupling .............................................................57
4.3 Subtractive Processing with Cryogenic Milling .................................57
4.3.1 General Considerations for Subtractive Processing ........................57
4.3.2 Cryogenic Machining Approach ...................................................58
4.3.3 Cryogenic Machining from the Materials Viewpoint ........................60
4.3.4 Cryogenic Machining of Additively Manufactured Ti-6Al-4V .............62
4.3.5 Principle Hardware for Cryogenic Milling with CO2..........................66
4.3.6 Intelligent Tool Spindle Future Part of the Process Data Model ........69
4.3.7 Carbon Dioxide Weighing Equipment and Switching Station ............70
4.3.8 Protective Measures for Safe Use of Cryogenic CO2 .......................72
4.4 Handling System .........................................................................74
4.4.1 Framework Considerations .........................................................74
4.4.2 Twin Robot System in the Initial State .........................................76
4.4.3 Integration of the ATHENA Turntable ...........................................79
4.4.4 Robot Calibration ......................................................................81
4.5 Lighting for Visual Inspection ........................................................84
4.6 Critical Design Review by ESA .......................................................84
5. Implementation and Validation ......................................... 85
5.1 Powdery Filler Material Selection ...................................................85
5.2 Basic Parameter Set for Additive Manufacturing ..............................87
5.2.1 Operating Point Selection ...........................................................87
5.2.2 Characterization and evaluation ..................................................89
5.2.3 Substrate to Structure Transition ................................................95
5.3 Energy Source Coupling ...............................................................99
5.3.1 Process Development ................................................................99
5.3.2 As-built Surface Treatment ...................................................... 103
5.3.3 Heat Treatment ...................................................................... 104
5.3.4 Mechanical Testing .................................................................. 106
5.3.5 Fractured Surfaces .................................................................. 108
5.3.6 Microstructure ........................................................................ 110
5.3.7 Linear Expansion Coefficient ..................................................... 113
5.4 Cryogenic Milling ....................................................................... 114
5.4.1 Strategy Approach .................................................................. 114
5.4.2 Milling Implementation ............................................................ 116
5.4.3 Technical Cleanliness ............................................................... 120
5.4.4 Accuracy and Duration ............................................................. 122
5.4.5 Surface Roughness.................................................................. 122
5.5 Process Data Model ................................................................... 123
6. Final Discussion and Conclusions..................................... 130
6.1 Summary ................................................................................. 130
6.2 Conclusions .............................................................................. 131
6.3 Outlook .................................................................................... 132
III. List of Figures ...................................................................... I
IV. List of Tables .................................................................. VIII
V. References ......................................................................... IX
VI. Symbols and Units ....................................................... XXXVI
VII. Abbreviations .............................................................. XXXIX
VIII. Annex I ............................................................................ XLI
IX. Annex II ....................................................................... XLIII
X. Annex III ....................................................................... XLIV
XI. Annex IV.......................................................................... XLV
XII. Annex V ......................................................................... XLVI
XIII. Annex VI....................................................................... XLVII
XIV. Annex VII ................................................................... XLVIII
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:78867 |
| Date | 19 April 2022 |
| Creators | Seidel, André |
| Contributors | Leyens, Christoph, Zimmermann, Martina, Bavdaz, Marcos, Technische Universität Dresden, European Space Agency |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | info:eu-repo/grantAgreement/Fraunhofer-Gesellschaft/Fraunhofer Lighthouse Project/Lighthouse Project EVOLOPRO//Evolutionary self-adaptation of complex production processes and products/EVOLOPRO, info:eu-repo/grantAgreement/Fraunhofer-Gesellschaft/Fraunhofer Lighthouse Project/Lighthouse Project SWAP//Hierarchical swarms as production architecture with optimized utilization/SWAP |
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