ILVDIPL.-ING. ALFRED G. ARLT

Laser Welding: Line Scanners for Beam Shaping and Guiding

Alfred G. Arlt

Ingenieurbüro für Lasertechnik +Verschleißschutz (ILV)Ingenieurbüro für Lasertechnik Verschleißschutz (ILV)Sulzbacher Str. 4

65824 Schwalbach/Taunus

@il lt daga@ilv-arlt.de

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ILVDIPL.-ING. ALFRED G. ARLT

History of ILV:

April 1988 Founded as one-men firm by the owner Alfred G. ArltProcess developmentConsulting and trainingMarketing of (own) technology patents

January 1989 Expanding activitiesConception, sales and set upof turnkey systems for Laser material processing(Together with ILV contractors)

January 1993 Expanding activitiesDevelopment, manufacturing and salesof own Laser optics and sensors

Scanners for Surface Treatment Scanners for Welding Seam Finder Special Beam Delivery Systems

June 2011 Expanding activitiesFounding of ILV AnwendungstechnikFounding of ILV-Anwendungstechnikwith 5 low and medium power Laser systemsfor process development, research and job shop work(Marking, welding of plastics and metal, surface treatment)

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ILVDIPL.-ING. ALFRED G. ARLT

Progress in Laser DevelopmentLasers (cw) for material processing

Type Industrially Beam Quality Focus Diameter Power up toType Industriallyavailable since

Beam Quality(M2)*

Focus Diameter(mm)**

Power up to(kW)

Nd:YAGLamp pumped

1970 75 0.810 5

CO 1984 1 7 0 170 20CO2Fast axial flow

1984 1.7 0.170 20

CO2Diffusion cooled

1994 1.1 0.110 8

Nd:YAGDiode pumped

1997 35 0.380 5

DiodeFiber coupled

1997 20 0.400 6

Disc (Yb:YAG) 2003 1.3 0.014 16

Fiber (Yb-Glas)Multi mode

2004 1.3 0.014 30

Fiber (Yb-Glas)Single mode

2005 1.05 0.011 10

*) Typical values for 2000 W Lasers **) f = 200 mm and 25 mm beam diameter on focusing optic

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ILVDIPL.-ING. ALFRED G. ARLT

The table before shows the continuous improvement of beam quality, with shorter development cycles during the last 10 years.

Today, focus diameters of 150 µm and less are state of the art for high-power lasers.

In many cases these spots are too narrowfor being suitable for welding parts with tolerances and gaps > 0,1 mm

In order to solve this problem and also to cover a wide range of applications, flexible optical systems are required to adjust the beam shape on the material surface according to the needs of part geometry, tolerances and/or the type of processing.

Typical Power Density for different Applications:Typical Power Density for different Applications:

Plastic Welding: 100 W/cm2

Transformation Hardening 2.000 W/cm2

Cladding: 50.000 W/cm2

Head Conduction Welding: 400 000 W/cm2Head Conduction Welding: 400.000 W/cm2

Deep Penetration Welding: ≥ 1.000.000 W/cm2

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ILVDIPL.-ING. ALFRED G. ARLT

One way to achieve the required power density on the work piece in an area of suitable geometry, is to move a laser beam of sufficient power along one axis back and forth, fast enough*) to transfer the laser energy into the work piece quasi-simultaneously instead of modifying the laser beam profile itselfsimultaneously, instead of modifying the laser beam profile itself.

For specific purposes a two-dimensional movement is also possible.

Th fi h th i i l t f liThe figure shows the principal set up of a line scannerto be used with fiber-coupled high power lasers.

With such a unit, frequencies of up to 1000 Hz and amplitudes of up to 20 mm (@ f=200 mm & frequency ≤150 Hz) are achievable. p (@ q y )

Advanced controllers (see picture) for this type of scanners also offer the possibility to deliver different levels of laser power along the scan line.

With direct water cooled scan mirrors, the actual maximum cw-power possible is 30 kW.

*) E i f l t b ldi d h t t t tExperience from electron beam welding and heat treatment,as well as first tests with line scannersby ILV during the mid-1990s showed thattypical scan frequencies must be set to ≥100 Hz

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ILVDIPL.-ING. ALFRED G. ARLT

During dynamic beam shaping at given feed rate the weld seam width is no longer determined by the laser focus spot on the work piece but rather by the elongation amplitude perpendicular to the feed direction.

The corresponding power density is then calculated from the laser power, the spot size, and the scan width. To achieve a continuous weld seam, the scanner frequency and the linear feed rate must be set in a way that sufficient overlap is generated. The net power density should be in the range of the power density, required for the chosen process.

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ILVDIPL.-ING. ALFRED G. ARLT

Line scanners from ILV are available as add-on for standard welding optics or as stand-alone units with and without transmissive beam shaping components.

Examples:

Source: Precitec, Gaggenau Source: Trumpf Laser- und Systemtechnik, Ditzingen DCY-Scanner (Stand-alone unit)

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ILVDIPL.-ING. ALFRED G. ARLT

Specifications of ILV DC- and DCY-Scanners

Maximum laser power : 30 kWMaximum frequency : 1000 HzMaximum amplitude : 20 mm (f = 200 mm) ≤ 150 HzMaximum amplitude : 20 mm (f = 200 mm), ≤ 150 Hz

3 mm (f = 200 mm), ≤ 250 Hz0.7 mm (f = 200 mm), ≤ 600 Hz

Controller Power supply : AC 230 V, 50 Hz (others on demand)Power consumption : 1500 W (max.)

Mirror unit

Maximum mirror diameter : 65 mmType of mirrors : copper, coated copper, coated aluminumCooling water flow : Minimum 5 liters per minuteg pCooling water pressure : Maximum 5 barMirror operating temperature : 15 to 60°C

Laser Power Control : 32 fields along scan axistime base generated by scanner controller

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Diagrams of Power Control Settings

ILVDIPL.-ING. ALFRED G. ARLT

Examples for Beam Shaping

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ILVDIPL.-ING. ALFRED G. ARLT

Beam Guiding Welding with Dynamic Power Control

Line scan with variable power densitypower density

Lap weld, scan width = 3.0 mm

Laser Weld(shaft material X46Cr13)

4-sheet butt weld, scan width = 3.5 mm

Dynamic power control: Welding high carbon steel without

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Dynamic power control: Welding high carbon steel without cold cracking

ILVDIPL.-ING. ALFRED G. ARLT

Application ExampleTube to Tube Connection

TIG Weld Laser Weld, scan width 1.8 mm

Laser Weld, cross section

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ILVDIPL.-ING. ALFRED G. ARLT

Production System with Optic for Dynamic Beam Shaping and GuidingWelding of parts for railway vehicles

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Source: Sondermaschinenbau Calvörde

ILVDIPL.-ING. ALFRED G. ARLT

DC- and DCY-Scanner used in Production of Automotive Parts(Selected)

Drive shaftsDrive shaftsMore than 5 Million parts welded since 2002

Exhaust silencer tubesMore than 2 Million parts welded since 2004

Car door bodyMore than 2 Million parts welded since 2005

EGR-Bypass Flaps with 14 different welds per partEGR-Bypass Flaps with 14 different welds per partMore than 1.6 Million parts welded since 2007

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