QUALITÄT SICHERN LASERPROZESSE ÜBERWACHEN

Transcription

1 QUALITÄT SICHERN LASERPROZESSE ÜBERWACHEN Stefan Kaierle WLT SHORT COURSE BASISWISSEN LASER UND LASER- MATERIALBEARBEITUNG, Stuttgart Laser Zentrum Hannover, Germany Contributions by:

2 STATEMENT The best sensor is no sensor! 2

3 LASER APPLICATIONS IN AUTOMOTIVE MANUFACTURE Source: VOLVO 3

4 OUTLINE Short History Motivation Examples of Automotive Companies New Approaches for: Laser Brazing Welding / Remote Welding Laser Depth Measurement Summary/Outlook 4

5 From Lab to Fab - Challenges on the path to serial production Since the start of the utilisation of process monitoring devices in serial production significant progress has been made on the path to market maturity Development leaps in material and device development, as well as in the development of processes and plant technology are significant factors Basic research, which means, complete understanding of the beammaterial interaction in combination with the use of ideal tools, is the key factor for the successful transfer Research institutions and innovative companies were and are the drivers bringing ideas from the lab to fully developed, reliable system technology into serial production (Markus Kogel Hollacher) Precitec KG, MKH 5

6 Beginnings Patents: 1984, Gerd Herziger, Eckhard Beyer, Peter Loosen, Reinhart Poprawe 1987, Robert Bosch GmbH, Werner Müller, Friedrich Dausinger, Eckart Roda 1989, Jurca Optoelektronik GmbH, Marius Jurca 1991, Fraunhofer ILT, Dora Maischner, Peter Abels, Alexander Drenker, Eckhard Beyer 1998, Fraunhofer ILT, Christian Kratzsch, Stefan Kaierle, Peter Abels First introduction of the Pre-, In-, Post - Process areas to be monitored with one device Precitec KG, MKH 6

7 MOTIVATION: MONITORING QUALITY PARAMETERS Quality Parameters suitable for in-process monitoring Geometry of seam at surface Pores at surface Splatter Width of kerf Cladded geometry 7

8 Correlation MOTIVATION: MONITORING QUALITY PARAMETERS Process parameters Geometry of melt pool Surface features Temperature radiation Plasma radiation Quality Parameters unsuitable for in-process monitoring Microstructure Lack of fusion Adhesion of dross Ripples at cutting Strength behaviour 8

9 MOTIVATION: ASSURING REPRODUCIBLE PROCESS PARAMETERS Parameter setup at machine control Laser power Feed rate Focal position TCP position Process variables Laser power at workpiece Relative movement between processing head and workpiece Focal position e.g. depending on temperature 9

10 DETECTION OF PROCESS PARAMETERS Source of Information Detectable Parameters (e.g.) Geometric Parameters Triangulation sensors CMOS cameras Thermal Parameters IR-cameras Pyrometer Incident and reflected/emitted radiation in laser materials processing General Parameters process stability feed rate / speed of motion product quality 10

11 OUTLINE Short History Motivation Examples of Automotive Companies New Approaches for: Laser Brazing Welding / Remote Welding Laser Depth Measurement Summary/Outlook 11

12 QUALITY ASSURANCE AT VOLVO Source: VOLVO 12

13 QUALITY ASSURANCE AT VOLVO Source: VOLVO 13

14 QUALITY ASSURANCE AT BMW Source: BMW 14

15 QUALITY ASSURANCE AT BMW Source: BMW 15

16 QUALITY ASSURANCE AT DAIMLER VISIR : Source: Daimler 16

17 QUALITY ASSURANCE AT DAIMLER VISIR : Source: Daimler 17

18 OUTLINE Short History Motivation Examples of Automotive Companies New Approaches for: Laser Brazing Welding / Remote Welding Laser Depth Measurement Summary/Outlook 18

19 BRAZING Source: Volkswagen 19

20 QUALITY CONTROL SYSTEM FOR LASER BRAZING NIR Camera: nm Frame rate: 140 fps Pixel-resolution: 320x130 CMOS Camera: 808 nm Frame rate: 350 fps Pixel-resolution: 1024x360 Illumination-Laser: Power: 20 W Wavelength: 808 nm Process: Nd:YAG-power: 1.3 kw Velocity: 1.3 m/min Zinc coated steel Copper based filler wire 20

21 QUALITY CONTROL SYSTEM FOR LASER BRAZING Detection of different process parameters: Brazing velocity (VIS) Misalignment of the laser spot (NIR) Brazing wire position & orientation relative to the laser spot (VIS) Detection of different seam imperfections: Pore detection with diameters less than 200 µm (NIR) Wetting behaviour (NIR) Surface quality (NIR / VIS) Example for misalignment of the laser spot 21

22 QUALITY CONTROL SYSTEM FOR LASER BRAZING Detection of brazing wire position & orientation relative to the laser spot VIS image 808nm) Brazing wire NIR image (thermal nm) Laser spot 22

23 QUALITY CONTROL SYSTEM FOR LASER BRAZING Process visualisation: External illumination (808 nm) t exp = 0.1 ms Frame-rate = 350 fps Process parameters Quality Control Thermal radiation: nm t exp = 0.5 ms Frame-rate = 100 fps Seam imperfections < 200 µm Pores Brazing wire Melt pool Non fused brazing wire 1 mm Seam 23

24 WELDING Source: Audi 24

25 WELDING MELT POOL GEOMETRY Experimental Setup Disk Laser BEO D70 3 mm steel-sheet P L = 3,5 kw v = 2 m/min Laser Camera Optics 1 mm 25

26 WELDING MELT POOL GEOMETRY Automatic Geometry Detection Development of Algorithms: Origin 640 x 256 pixels Frame-rate 3 khz Pre-Processing Smoothing Threshold Calculated Geometry Width, height Center of gravity 26

27 SPECTRAL CONTROL OF WELDING DEPTH data evaluation power control power control spectrometer laser source laser processing head steel laser beam laser process aluminum 27

28 SPECTRAL CONTROL OF WELDING DEPTH LASER WELDING HEAD Provided by Laser parameters core diameter: 600 µm collimation: 200 mm focusing length: 280 mm focus diameter: 840 µm maximum laser power: 4 kw Process parameters used laser power: kw feed rate: 3.5 to 4.0 m/min gap: 0 and 0.1 mm focus position: -1 mm inert gas: argon collimation reflection mirror nm reflection mirror for spectrometry nm nm reflection mirror nm scanner mirror nm nm focusing nm nm spectrallines 28

29 relative intensity SPECTRAL CONTROL OF WELDING DEPTH Materials: H360LA AA6016 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, , , ,5 wave length [nm] 394,5 und 396,2 nm characteristic emission line for Al 29

30 HYBRID WELDING OF THICK SHEET METALS 30

31 XXL-SURFACING: LASER GUIDED ARC WELDING (CLADDING) Problem: Self positioning of the electric arc on the highest position No contact to both layers Beam diameter: Focus position 1 mm +3mm Process speed 900/ 800mm/min 31

32 XXL-SURFACING laser assisted double wire surfacing Advantages: minimal heat input low dilution high deposition rate 32

33 XXL-SURFACING 33

34 XXL-SURFACING 30 mm welded surface, not machined 34

35 Welding Depth Measurement New sensor device Low Coherence Interferometry PRECIT EC IDM System Light Source Sensor Referenzarm Bearbeitungslaser Beam Splitter Fixed Reference Mirror Messarm Workpiece Bearbeitungsebene z y x PRECITEC GmbH & Co. KG Dr. Markus Kogel-Hollacher 38

36 The IDM system technology Sensor optics interface at the processing head - Shift of the measurement spot in the x, y - Adaptation of the aperture possible Variable optical reference path - Adaption to different measuring distances possible Technology for signal processing - Sensor for detecting the modulated signal - Sensor output: Distance value (analogue or Ethernet) Software GUI : Parameterisation and display PRECITEC GmbH & Co. KG Dr. Markus Kogel-Hollacher 39

37 The IDM Measurements Power variations in 5mm St37 low carbon steel 3m/min., 400µm spot diameter PRECITEC GmbH & Co. KG Dr. Markus Kogel-Hollacher 40

38 The IDM Measurements Power variations in 5mm St37 low carbon steel 3m/min., 400µm spot diameter PRECITEC GmbH & Co. KG Dr. Markus Kogel-Hollacher 41

39 The IDM Measurements Power variations in 5mm St37 low carbon steel 3m/min., 400µm spot diameter Transfer from keyhole welding To heat conduction welding closing capillary PRECITEC GmbH & Co. KG Dr. Markus Kogel-Hollacher 42

40 The IDM Measurements Power variations in 5mm St37 low carbon steel 3m/min., 400µm spot diameter PRECITEC GmbH & Co. KG Dr. Markus Kogel-Hollacher 43

41 The IDM Measurements Power variations in 5mm St37 low carbon steel 3m/min., 400µm spot diameter PRECITEC GmbH & Co. KG Dr. Markus Kogel-Hollacher 44

42 The IDM Measurements Power variations in 5mm St37 low carbon steel 3m/min., 400µm spot diameter Transfer from keyhole welding To heat conduction welding closing capillary PRECITEC GmbH & Co. KG Dr. Markus Kogel-Hollacher 45

43 SUMMARY / OUTLOOK 1 st Generation Process Control (integrating measurement photo diodes, pyrometer) still successfully in use 2 nd Generation Process Control: Camera based (VIS, IR) Measurement of direct and non-direct process parameters Trend: combination of various detectors simultaneously Latest Development: Measuring Penetration Depth by LCI (Low Coherence Interferometry) 46

44 THANK YOU Contact: Dr. Stefan Kaierle Laser Zentrum Hannover, Germany