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An Investigation on the Printing of Metal and Polymer Powders Using Electrophotographic Solid Freeform Fabrication

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An Investigation on the Printing of Metal and Polymer Powders Using Electrophotographic Solid Freeform Fabrication AN INVESTIGATION ON THE PRINTING OF METAL AND POLYMER POWDERS USING ELECTROPHOTOGRAPHIC SOLID FREEFORM FABRICATION By AJAY KUMAR DAS A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2004 Copyright 2004 by Ajay Kumar Das Dedicated to my mother. ACKNOWLEDGMENTS I extend my sincere gratitude to my advisor and chairman of the thesis committee, Dr. Ashok V. Kumar for his guidance and support during the research work which made this thesis possible. I would also like to thank the thesis committee members Dr. John K. Schueller and Dr. Nagaraj Arakere for their patience in reviewing the thesis and for their valuable advice during the research work. I thank the Design and Rapid Prototyping Laboratory co-workers for being helpful, supportive and making the research a pleasurable experience. Last but not least, I would like to thank my parents for their love and encouragement during my studies abroad. iv TABLE OF CONTENTS Page ACKNOWLEDGMENTS ................................................................................................. iv LIST OF TABLES............................................................................................................. ix LIST OF FIGURES ........................................................................................................... xi ABSTRACT.......................................................................................................................xv CHAPTER 1 INTRODUCTION ........................................................................................................1 Electrophotographic Solid Freeform Fabrication (ESFF) ............................................1 Past Research and Motivation for the Present Work....................................................2 Chapter Layout .............................................................................................................3 2 RAPID PROTOTYPING..............................................................................................6 Stereolithography Apparatus (SLA).............................................................................8 Solid Ground Curing (SGC) .........................................................................................9 Selective Laser Sintering (SLS)..................................................................................10 Fused Deposition Modeling (FDM) ...........................................................................11 Laminated Object Manufacturing (LOM) ..................................................................12 3-D Printing ................................................................................................................14 3 ELECTROPHOTOGRAPHY.....................................................................................16 The Electrophotographic Process ...............................................................................16 Photoconductor Material ............................................................................................18 Dark Decay..........................................................................................................18 Charge Acceptance..............................................................................................19 Image Formation Time........................................................................................19 Image Stability.....................................................................................................19 Residual Image ....................................................................................................19 Material Selection................................................................................................20 Charging ..............................................................................................................21 Corona Charger ............................................................................................21 Charge Roller ...............................................................................................23 Imaging................................................................................................................23 v Development........................................................................................................24 Cascade Development ..................................................................................25 Magnetic Brush Development......................................................................26 Conductive Magnetic Brush Development ..................................................27 Mono-component Development...................................................................28 Charged and Discharged Area Development ...............................................28 Toner Powder Charging ...............................................................................30 Transfer................................................................................................................32 Fusing ..................................................................................................................33 Cleaning...............................................................................................................33 4 ELECTROPHOTOGRAPHIC SOLID FREEFORM FABRICATION (ESFF)........34 Development of ESFF Test-bed System.....................................................................35 Motion Control System .......................................................................................36 Printing ................................................................................................................37 Fusing ..................................................................................................................37 Software...............................................................................................................38 Measurement of Charge and Mass of Powder............................................................39 Measurement of Powder Properties............................................................................40 Improvement of Print Quality.....................................................................................40 Limitation on Part Height....................................................................................40 Edge Growth (Solid Area Development) ............................................................42 Printing of Powders other than Toner.........................................................................43 Study of Laser Imager System of Printer ...................................................................45 5 DESIGN AND TESTING OF IMAGE DEVELOPERS............................................47 Developer Design .......................................................................................................48 Powder Box .........................................................................................................50 Developer Roller .................................................................................................50 Developer Roller Casing .....................................................................................51 Pivoting Blade Powder Developer ......................................................................53 Development of Charge and Mass Measurement Test Setup.....................................56 Discussion on Development of First Test Setup and Testing Concepts..............56 Improvement in the Design of Test Setup...........................................................59 Independent Charge and Mass Measurement Test Setup...........................................63 Design Considerations.........................................................................................64 Stages of Charge and Mass Measurement Test Cycle.........................................67 Design and Building of the Charge and Mass Measurement Test Setup ............68 Transfer Drum Assembly.............................................................................68 Cleaner Box Assembly.................................................................................70 Motor and Stand Assembly..........................................................................71 Experimental Results..................................................................................................73 Experiments with Iron Powder............................................................................73 Experiments with Nylon – 12 Powder.................................................................75 vi 6 METAL POWDER DEVELOPMENT AND PRINTING.........................................77 Metal Powder Development .......................................................................................78 Metal Development Theory........................................................................................80 Constant Parameters used in Calculations...........................................................80 Charge per Unit Mass (Q/M) Calculations..........................................................81 Maximum Surface Charge Density .....................................................................83 Electric Field Range ............................................................................................84 Calculation of Forces Involved During Development.........................................85
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