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Monitoring and Control of Robotized Laser Metal-Wire Deposition
University West, Department of Engineering Science, Division of Electrical and Automation Engineering. (PTW)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis gives a number of solutions towards full automation of the promising manufacturing technology Robotized Laser Metal-wire Deposition (RLMwD). RLMwD offers great cost and weight saving potentials in the manufacturing industry. By metal deposition is here meant a layered manufacturing technique that builds fully-dense structures by melting metal wire into solidifying beads, which are deposited side by side and layer upon layer. A major challenge for this technique to be industrially implemented is to ensure process stability and repeatability. The deposition process has shown to be extremely sensitive to the wire position and orientation relative to the melt pool and the deposition direction. Careful tuning of the deposition tool and process parameters are therefore important in order to obtain a stable process and defect-free deposits. Due to its recent development, the technique is still manually controlled in industry, and hence the quality of the produced parts relies mainly on the skills of the operator. The scientific challenge is therefore to develop the wire based deposition process to a level where material integrity and good geometrical fit can be guaranteed in an automated and repeatable fashion. This thesis presents the development of a system for on-line monitoring and control of the deposition process. A complete deposition cell consisting of an industrial robot arm, a novel deposition tool, a data acquisition system, and an operator interface has been developed within the scope of this work. A system for visual feedback from the melt pool allows an operator to control the process from outside the welding room. A novel approach for automatic deposition of the process based on Iterative Learning Control is implemented. The controller has been evaluated through deposition experiments, resembling real industrial applications. The results show that the automatic controller increases the stability of the deposition process and also outperforms a manual operator. The results obtained in this work give novel solutions to the important puzzle towards full automation of the RLMwD process, and full exploitation of its potentials.

Place, publisher, year, edition, pages
Göteborg: Chalmers University of Technology , 2012. , 186 p.
Series
Doktorsavhandlingar vid Chalmers tekniska högskola, ISSN 0346-718X ; 3336
Keyword [en]
Laser Metal Wire Deposition, Additive Layer Manufacturing, Robotic Weld Equipment, Optical Sensors, Process Control, Process Development, Process Stability, Iterative Learning Control
National Category
Robotics Control Engineering
Identifiers
URN: urn:nbn:se:hv:diva-4206ISBN: 978-91-7385-655-3 (print)OAI: oai:DiVA.org:hv-4206DiVA: diva2:509955
Public defence
2012-03-23, F123, Högskolan Väst, Trollhättan, 10:00 (English)
Opponent
Available from: 2012-03-26 Created: 2012-03-14 Last updated: 2015-10-02Bibliographically approved
List of papers
1. Visual feed-back for operator interaction in robotized laser metal deposition
Open this publication in new window or tab >>Visual feed-back for operator interaction in robotized laser metal deposition
2008 (English)In: Proceedings of the 22nd International Conference on Surface Modification Technologies SMT22: Held at University West, Trollhättan, Sweden September 22-24, 2008 / [ed] T.S. Sudarshan & Per Nylen, 2008, 297-304 p.Conference paper, Published paper (Other academic)
Series
Surface Modification Technologies, 22
National Category
Metallurgy and Metallic Materials
Research subject
ENGINEERING, Mechatronics; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-2249 (URN)978-0-9817065-1-1 (ISBN)
Conference
Surface Modification Technologies SMT22
Available from: 2010-03-03 Created: 2010-03-03 Last updated: 2016-02-09Bibliographically approved
2. Increased stability in laser metal wire deposition through feedback from optical measurements
Open this publication in new window or tab >>Increased stability in laser metal wire deposition through feedback from optical measurements
2010 (English)In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 48, no 4, 478-485 p.Article in journal (Refereed) Published
Abstract [en]

Robotized laser metal-wire deposition is a fairly new technique being developed at University West in cooperation with Swedish industry for solid freeform fabrication of fully densed metal structures. It is developed around a standard welding cell and uses robotized fiber laser welding and wire filler material together with a layered manufacturing method to create metal structures. In this work a monitoring system, comprising two cameras and a projected laser line, is developed for on-line control of the deposition process. The controller is a combination of a PI-controller for the bead width and a feed-forward compensator for the bead height. It is evaluated through deposition of single-bead walls, and the results show that the process stability is improved when the proposed controller is used.

Keyword
Laser deposition, metal wire, machine vision, process control, robotic welding equipment
National Category
Control Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-2082 (URN)10.1016/j.optlaseng.2009.08.012 (DOI)000275074900011 ()
Projects
RMS
Available from: 2009-12-28 Created: 2009-12-28 Last updated: 2016-02-09Bibliographically approved
3. Height control of laser metal-wire deposition based on iterative learning control and 3D scanning
Open this publication in new window or tab >>Height control of laser metal-wire deposition based on iterative learning control and 3D scanning
2012 (English)In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 50, no 9, 1230-1241 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Laser metal deposition; Additive layer manufacturing; Metal wire; Iterative learning control; 3D scanning
National Category
Robotics Control Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-4203 (URN)10.1016/j.optlaseng.2012.03.016 (DOI)000305773200008 ()2-s2.0-84861592745 (Scopus ID)
Available from: 2012-03-14 Created: 2012-03-14 Last updated: 2016-02-08Bibliographically approved
4. Towards stable high-speed metal-wire deposition, Part I: Parameter study
Open this publication in new window or tab >>Towards stable high-speed metal-wire deposition, Part I: Parameter study
Show others...
(English)In: Journal of laser applications, ISSN 1042-346XArticle in journal (Refereed) Submitted
National Category
Robotics Control Engineering Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-4204 (URN)
Available from: 2012-03-14 Created: 2012-03-14 Last updated: 2014-05-08Bibliographically approved
5. Towards stable high-speed metal-wire deposition, Part II: Automatic deposition using feedback control
Open this publication in new window or tab >>Towards stable high-speed metal-wire deposition, Part II: Automatic deposition using feedback control
(English)Article in journal (Refereed) Submitted
National Category
Robotics Control Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-4205 (URN)
Available from: 2012-03-14 Created: 2012-03-14 Last updated: 2014-10-29Bibliographically approved

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