COMPOSITE TECHNOLOGIES FOR INTELLIGENT INDUSTRIAL LASER PROCESSING prof. VINCENZO PIURI Department of Information Technologies, University of Milan via Bramante 65, 26013 Crema (CR), Italy EU Project SLAPS Self-Tuning and User-Independent Laser Material Processing Units Philips Centre for Industrial Technology Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Information Sources Partners in IMS/Brite-Euram Project SLAPS • Philips-CFT • Laser Zentrum Hannover • Odense Steel Shipyard LTD. • Jurca Opto-elektronik • Fiat-CRF • • • • Trumpf Lasag AG Politecnico di Milano Ecole Politechnique Federale de Lausanne - IOA • University of Vienna Contributions to the Tutorial: Prof. Cesare Alippi, Politecnico di Milano, Italy Dr. Toon Bloom, Philips CFT, The Netherlands Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Laser Processing Applying energy to a work piece in the form of (high intensity) light beam • • • • • • • • Laser seam welding Laser cutting Laser spot welding Laser drilling Laser cladding Laser marking Laser adjustment …... Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Carbon Dioxide Laser Typical gas laser construction Discharge power supply Gas mixture Brewster windows Cavity end mirrors Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Output beam Nd:YAG Laser Laser beam out Folding mirror Nd:YAG rod Flash lamp Water cooling circuit Lamp driver Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Solid State Laser Diode n-type AlGaAs GaAs p-type AlGaAs -eV EC EF EV Three layer structure in equilibrium n-type AlGaAs GaAs p-type AlGaAs EC -eV - - EFN h EFP + + EV Three layer structure with forward current Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Solid State Laser Diode • Low output power • Laser diode arrays for processing • Low beam quality • Good control qualities • High efficiency HE AT SIN K Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 P-GaAs P-GaALAs GaAlAs (active layer) N-GaAlAS N-GaAs Beam Delivery Cavity Beam expanding and collimating Focussing mirror Translating and rotating mirrors Beam manipulation over multiple (5) axis Work piece Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Beam Delivery Fibre Cavity Collimator lens Glass fibre delivery Scanning mirrors F1 Process monitoring F2 Spot size = Fibre core diameter x F1 F2 Work piece Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Absorption, Reflection, Transmission • Kirchhoff: Absorption +reflection+transmission = 1 • Extinction of the penetrating light wave Io I ( x ) Ioe I(z) 4kx Ioe 2x 1/e • Penetration depth: x 1 co 1 2k co of Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Absorption and Heat Diffusion = F(T) D a Stainless steel D a Copper Temperature D Temperature a Aluminium Temperature Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Process Phases • 1: Heating: Absorption, heat diffusion • 2: Phase transition of top material, change of properties • 3: Vaporisation, recoil pressure pushes liquid metal aside • 4: Liquid level reaches bottom and is blown out Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Laser Cutting Laser beam Laser beam Movement Top view laser cutting Cross section laser cutting • Medium to high power CW lasers (CO2) • Process gas, reactive (O2. extra reaction energy) or not (N2), to blow out molten material • Wave guide kind of energy transfer through the cutting slit Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Spark Pattern During Laser Cutting Good quality cutting Laser beam Laser beam Bad quality cutting Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Process Monitoring Focussing mirror 1- Optical emission from processing area * Photo diode * spectrometer 2- Impedance measurement Reactive: Nozzle - work piece distance Resistive: Plasma detection 3- Spreading of sparks Process gas A V work piece CCD Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Laser Seam Welding Part B Part B Part A Part A But-joint Part B Lap joint Part A T-joint Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Laser Seam Welding Laser beam Laser beam Movement Undesired porosity Seam weld Keyhole Gap / slit Top view seam welding • • • • Cross section seam welding Battery casings, Pace maker casings Car bodies, Transmission parts Sub assemblies in ship building Plastics (overlap penetration welding) Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Laser Seam Welding Process monitoring - Direct delivery system Focussing mirror Optical emission from processing area * Photo diode * spectrometer Input power monitoring Process gas 2-D thermal imaging work piece Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Laser Seam Welding Laser Fibre Collimator lens Process monitoring - Fibre delivery system Sensing implemented in processing head Scanning mirrors Temperature Plume emission Reflected Laser power Input laser power Work piece Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Spot Weld Geometries Overlapfillet O verlappenetration N os e w eld Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 CCD camera 200 micron fibre Process Monitoring in spot welding Surface temperature Plume emission Nd:YAG filter X/Y scanning mirror Reflected power Laser input power Acoustic emission Work piece Eddy current losses Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 Signal Processing Example of measured signals Spot welding of 2 x 100 micron copper sheets 400 micron spot, 4000 Watt square pulse 3.5 LMO 3 Plume 2.5 Temp lin 2 Temp log Volts 1.5 1 0.5 0 -0.5 -1 0 1 2 3 4 5 6 Time [ms] Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 7 8 Signal Processing Example of measured signals Spot welding of 2 x 100 micron copper sheets 400 micron spot, 3500 Watt square pulse 4.5 LMO 4 Temp lin 3.5 3 Temp log 2.5 Volts Eddy 2 1.5 1 0.5 0 -0.5 -1 0 1 2 3 4 5 6 Time [ms] Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002 7 8 Automatic Classification based on multi sensor process monitoring • The complete set of sensors provides a broad information range about the performance of the process • Realisation of data reduction by extraction of specific features from the recorded signals • The features are recognised as being related to certain process events • The relations between features and a good or bad performing process have to be established through a large set of verification experiments Vincenzo Piuri, SIcon/02, Houston, TX, USA, 18-21 November 2002
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