Laser Metal Deposition (LMD) is a promising technique for fabrication of large metallic parts directly from 3D CAD models. However, the complexity of the process makes it challenging to prevent geometrical distortions and defects to affect the fabricated parts. On-line monitoring and control are fundamental issues to mitigate these problems, but they are not efficiently enough provided by current LMD techniques. As the first step in the development of an efficient unified on-line monitoring and control system for LMD, this paper presents a novel on-line 3D monitoring system for part geometry measurement. The system is capable of working in real-time in robot coordinates, without imposing restrictions to the possible paths, orientations or speed of movement. The use of ROS and the self-calibration method also proposed in the paper provide a flexible, cost-effective solution to easily upgrade current industrial LMD robotized cells.

1. ROS-Based 3D On-Line Monitoring
for LMD Robotized Cells
Jorge Rodríguez-Araújo1, Juan J. Rodríguez-Andina2
1AIMEN Technology Center, Porriño, Spain
2Department of Electronic Technology, University of Vigo, Spain
INDIN2015, Cambridge, 23-7-2015

2. www.aimen.es | aimen@aimen.es 2
Index
1. Motivation and Innovative Character.
2. Proposed Solution.
3. 3D Geometrical Monitoring.
4. Self-Calibration.
5. Experimental Results.
6. Conclusions and future work.
Index

3. www.aimen.es | aimen@aimen.es 3
Motivation and Innovative Character

4. 4www.aimen.es | aimen@aimen.es
Motivation and Innovative Character
• Promising additive manufacturing technique.
– Parts are built up layer by layer directly from a 3D CAD model.
• For repair and direct fabrication of pieces.
• Near-net-shape (close to the final shape).
• Manufacturing of large metallic parts.
– The material is directly deposited on the previous
surface.
• Thermal heating accumulation produces geometrical distortions.
• Distortions rise in poor dimensional accuracy and defects.
• Traditional off-line process (with constant parameters)
becomes unsuccessful.
Laser Metal Deposition (LMD)
LMD Issues

5. 5www.aimen.es | aimen@aimen.es
Motivation and Innovative Character
• There are a lot of industrial robotized laser cells.
• Empower robotized laser cells for effective AM.
• Retrofit current industrial facilities.
• Apply state of the art robotic
software solutions.
Motivation
Robotized
Cladding Cell
Motion
Controller
Main Controller
Off-line
Path Planning
6-Axis
Robot
Laser
Powder
Feeder
Power
Controller
Flow
Controller
Innovation

6. www.aimen.es | aimen@aimen.es 6
Proposed Solution

7. 3D
triangulation
laser
fiber
working
table
power
control
6-axis
robot
powder
feeder
nozzle
7www.aimen.es | aimen@aimen.es
Proposed Solution
• On-line geometrical monitoring.
• Adaptive path planning.
LMD geometrical control
Robotized Laser Cell
Track MeasurementPath Planning
3D Model
Layer Planning Layer Measurement
STL Generation
On-line

8. 8www.aimen.es | aimen@aimen.es
Proposed Solution
3D scanning setup
• Industrial CMOS camera.
• Industrial RED laser stripe.
• Fixture to attach the components to the laser cladding head.
laser
stripe camera
cladding
head

9. www.aimen.es | aimen@aimen.es 9
3D Geometrical Monitoring

10. 10www.aimen.es | aimen@aimen.es
3D Geometrical Monitoring
3D Geometrical Monitoring
Industrial Robotic Laser Cell
Peak
Finder
CAMERA
IDS DRIVER
3D Point Cloud
Working Cell Coordinates
ROBOT
ROS-DRIVER
State
Publisher
Laser
Triangulation
Robot Pose
Tool-Camera
3D ProfileCamera Pose
Timestamp
• 3D point cloud (geometric information)
– On-line generation.
– In robot coordinates.
– Independently of the speed.
– No movement restrictions.
– Free orientation.
• Laser Stripe Detection
• Laser Triangulation
• Transformation to robot
coordinates
Monitoring main tasks

11. 11www.aimen.es | aimen@aimen.es
3D Geometrical Monitoring
• Center Of Gravity method as peak finder.
• Point correspondence for 2D-to-3D mapping solution.
• ROS-based
– Tf library
(interpolation)
3D profile calculation
Point cloud reconstruction
Peak
Finder
3D Point Cloud
Working
Cell Coordinates
Laser
Triangulation
3D Profile
Camera Pose
Timestamp
Calibration
3D Profile

12. 12www.aimen.es | aimen@aimen.es
3D Geometrical monitoring
ROS-Industrial components
ROBOT
ROS-DRIVER
State
Publisher
Robot Pose
Tool-Camera
Instantaneous
Camera Pose
Calibration + urdf
ROS-Driver (ABB Rapid)
Geometrical Description of the
Cell (urdf)

13. www.aimen.es | aimen@aimen.es 13
Self-Calibration

14. 14www.aimen.es | aimen@aimen.es
Self-Calibration
• Camera calibration (OpenCV method)
• Laser stripe calibration
• Hand-eye calibration (Classical method Tsai-Lenz)
Calibration steps

15. 15www.aimen.es | aimen@aimen.es
Self-Calibration
1. Checkerboard localization.
2. Laser stripe detection (RANSAC).
3. Laser plane estimation (RANSAC).
4. 2D-to-3D transformation matrix estimation.
Laser stripe calibration steps
1
2
3

16. www.aimen.es | aimen@aimen.es 16
Experimental results

17. Experimental results
www.aimen.es | aimen@aimen.es 17
On-line scanning
robscan.MP4

18. 18www.aimen.es | aimen@aimen.es
Experimental results
Results examples of direct scanning

19. 19www.aimen.es | aimen@aimen.es
Experimental Results
Processing results
Point cloud

20. www.aimen.es | aimen@aimen.es 20
Conclusions and Future Work

21. 21www.aimen.es | aimen@aimen.es
Conclusions and Future Work
• Complete the layer measurement module.
• Develop the on-line path planning system.
• Enable a full automatic LMD robotized cell.
Future work
Working area
LASHARE Project
http://www.lashare.eu/

22. www.aimen.es | aimen@aimen.es 22
AIMEN – Central y Laboratorios
c/ Relva 27 A
36410 – O PORRIÑO (Pontevedra)
Telf.+34 986 344 000 – Fax. +34 986 337 302
Delegación Tecnológica Madrid
Avda. del General Perón, 32, 8 A
28020 – MADRID (Madrid)
Telf.+34 687 448 915
Delegación Tecnológica A Coruña
Fundación Mans – Paideia
Pol. Pocomaco - Parcela D-22 - Oficina 20A
15190 – A CORUÑA (A Coruña)
Telf. +34 617 395 153
Thank you for your attention
Jorge Rodríguez Araujo | Research Engineer
Ph +34 986 344 000 | jorge.rodriguez@aimen.es