Height control of laser metal-wire deposition based on iterative learning control and 3D scanning

Laser Metal-wire Deposition is an additive manufacturing technique for solid freeform fabrication of fully dense metal structures. The technique is based on robotized laser welding and wire filler material, and the structures are built up layer by layer. The deposition process is, however, sensitive to disturbances and thus requires continuous monitoring and adjustments. In this work a 3D scanning system is developed and integrated with the robot control system for automatic in-process control of the deposition. The goal is to ensure stable deposition, by means of choosing a correct offset of the robot in the vertical direction, and obtaining a flat surface, for each deposited layer. The deviations in the layer height are compensated by controlling the wire feed rate on next deposition layer, based on the 3D scanned data, by means of iterative learning control. The system is tested through deposition of bosses, which is expected to be a typical application for this technique in the manufacture of jet engine components. The results show that iterative learning control including 3D scanning is a suitable method for automatic deposition of such structures. This paper presents the equipment, the control strategy and demonstrates the proposed approach with practical experiments.

[1]  Reinhart Poprawe,et al.  Identification and qualification of temperature signal for monitoring and control in laser cladding , 2006 .

[2]  M. Doubenskaia,et al.  Optical monitoring of Nd : YAG laser cladding , 2004 .

[3]  I. R. Pashby,et al.  Deposition of Ti–6Al–4V using a high power diode laser and wire, Part I: Investigation on the process characteristics , 2008 .

[4]  Richard W. Longman,et al.  Iterative learning control and repetitive control for engineering practice , 2000 .

[5]  N. Järvstråt,et al.  Modelling Ti-6Al-4V microstructure by evolution laws implemented as finite element subroutines: : Application to TIG metal deposition , 2008 .

[6]  Lin Li,et al.  A comparative study of wire feeding and powder feeding in direct diode laser deposition for rapid prototyping , 2005 .

[7]  João Paulo C. Rodrigues,et al.  Rapid prototyping with high power fiber lasers , 2008 .

[8]  Mohammad Jahazi,et al.  Optimization of bead spacing during laser cladding of ZE41A-T5 magnesium alloy castings , 2008 .

[9]  Omer Van der Biest,et al.  Wire based additive layer manufacturing: Comparison of microstructure and mechanical properties of Ti–6Al–4V components fabricated by laser-beam deposition and shaped metal deposition , 2011 .

[10]  B. Baufeld,et al.  Additive manufacturing of Ti–6Al–4V components by shaped metal deposition: Microstructure and mechanical properties , 2010 .

[11]  J. Mei,et al.  Laser fabrication of Ti6Al4V/TiC composites using simultaneous powder and wire feed , 2007 .

[12]  Huang Weidong,et al.  Research on molten pool temperature in the process of laser rapid forming , 2008 .

[13]  Radovan Kovacevic,et al.  Sensing, modeling and control for laser-based additive manufacturing , 2003 .

[14]  Bengt Lennartson,et al.  Increased stability in laser metal wire deposition through feedback from optical measurements , 2010 .

[15]  A.G. Alleyne,et al.  A survey of iterative learning control , 2006, IEEE Control Systems.

[16]  Suguru Arimoto,et al.  Bettering operation of Robots by learning , 1984, J. Field Robotics.

[17]  Frank W. Liou,et al.  Variable Powder Flow Rate Control in Laser Metal Deposition Processes , 2008 .

[18]  Dominique Grevey,et al.  Optimisation of refractory coatings realised with cored wire addition using a high-power diode laser , 2005 .

[19]  John J. Craig,et al.  Adaptive control of manipulators through repeated trials , 1984 .

[20]  Svante Gunnarsson,et al.  Time and frequency domain convergence properties in iterative learning control , 2002 .

[21]  D. L. Greene,et al.  Laser Engineered Net Shaping (LENS(TM)): A Tool for Direct Fabrication of Metal Parts , 1998 .

[22]  I. R. Pashby,et al.  Microstructure formation in Waspaloy multilayer builds following direct metal deposition with laser and wire , 2008 .

[23]  Ehsan Toyserkani,et al.  An image-based feature tracking algorithm for real-time measurement of clad height , 2007, Machine Vision and Applications.

[24]  Andrew J. Pinkerton,et al.  Combining wire and coaxial powder feeding in laser direct metal deposition for rapid prototyping , 2006 .

[25]  J. Nurminen.  Hot-wire laser cladding: Process, materials and their properties , 2008 .

[26]  K. Osakada,et al.  Rapid Manufacturing of Metal Components by Laser Forming , 2006 .

[27]  I. R. Pashby,et al.  Fibre laser metal deposition with wire: parameters study and temperature monitoring system , 2008, International Symposium on High Power Laser Systems and Applications.

[28]  Lin Li,et al.  Effects of wire feeding direction and location in multiple layer diode laser direct metal deposition , 2005 .

[29]  Yun Peng,et al.  Plunging method for Nd:YAG laser cladding with wire feeding , 2000 .

[30]  Gregory John Gibbons,et al.  Direct tool steel injection mould inserts through the Arcam EBM free‐form fabrication process , 2005 .

[31]  B. Previtali,et al.  Repairing of sintered tools using laser cladding by wire , 2005 .

[32]  R. Poprawe,et al.  Characterization of the process control for the direct laser metallic powder deposition , 2006 .

[33]  Reinhart Poprawe,et al.  Development and qualification of a novel laser-cladding head with integrated sensors , 2007 .

[34]  Weidong Huang,et al.  Estimation of laser solid forming process based on temperature measurement , 2010 .

[35]  Noboru Kikuchi,et al.  Closed loop direct metal deposition : art to part , 2000 .

[36]  Graham C. Goodwin,et al.  Control System Design , 2000 .

[37]  J. Mei,et al.  Microstructure study of direct laser fabricated Ti alloys using powder and wire , 2006 .

[38]  I. R. Pashby,et al.  Deposition of Ti–6Al–4V using a high power diode laser and wire, Part II: Investigation on the mechanical properties , 2008 .

[39]  Amir Khajepour,et al.  A mechatronics approach to laser powder deposition process , 2006 .

[40]  Christoph Leyens,et al.  Additive manufactured Ti-6Al-4V using welding wire: comparison of laser and arc beam deposition and evaluation with respect to aerospace material specifications , 2010 .