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SHEET METAL WELDING WITH KW ND:YAG LASERS FOR THE AUTOMOTIVE INDUSTRY.

Objective

The objectives of the proposed project are to establish the principles and the underlying conditions for the industrial application of kW range solid-state lasers for welding thin sheet, to illustrate the possibilities and the limits for both the kW solid state laser and the optical fibre and to determine the prospects for the application of such systems.
- Knowledge in the field of interaction between beam and material was gathered for zinc coated steel and aluminium alloys using laser beam intensities (10{5}-10{6} W/cm{2}) which are typical for kW Nd:YAG lasers with beam delivery via optical fibres.
- Laser welding has neither advantages nor disadvantages concerning the corrosional behaviour of zinc coated steel compared to resistance spot welding.
- Welding speed is between 2 and 7 m/min for steel sheets and between 0.6 and 2.9 m/min for aluminium alloy sheets, dependent on the type of seam and the laser source.
- Zinc coated steel sheets require a gap between 0.1 and 0.2 mm between the sheets during overlap welding. Otherwise, heavy spattering occurs, due to the low evaporation temperature of the zinc.
- Due to the higher reflections of the aluminium alloys, an angle of incident (15 degrees) between the surface of the workpiece and the output housing is required to prevent fibre damages.
- Hot cracking is problematic during overlap welding using the hardenable aluminium alloys of the 6000 group. Butt welding has a lower tendency to hot cracks, due to the decreased temperature gradient.
- Fibre cables and connectors were designed and successfully tested for industrial 3-D applications.
- A new 2 kW Nd:YAG is now available for welding applications in the automotive industry.
- An industrial output housing (tool head) with clearance control system for welding applications will be available in the near future to compensate for workpiece tolerances.
- Acoustic emissions can be detected for on-line process inspection and quality control.
- Simulation tools are useful to support the final design of clamping devices, and to detect collision problems of the robot.
- A list of requirements for the manipulation device (robot) was determined.
- The economic performance of the Nd:YAG welding process was compared to CO2 laser welding and to resistance spot welding. It was found to be attractive for certain applications, especially when additional sealing processes can be replaced by the welding.
- The running costs of continuous Nd:YAG lasers are much lower compared to pulsed Nd:YAG lasers, due to the longer lifetime of the pumping lamps.
- New applications for Nd:YAG laser welding in the automotive industry are possible if the design of the car body is adapted to the needs of the process.
For this purpose it will be necessary to carry out, evaluate and analyse welding of thin sheet. A detailed analysis of the interaction between beam and material is required in order to gain an understanding of the process.

This understanding will permit the deduction of the basic conditions required for industrial thin sheet welding and will allow the development and testing of measures and methods for inspecting, controlling and regulating the process.

Coordinator

Laser Zentrum Hannover eV
Address
Hollerithallee 8
30419 Hannover
Germany

Participants (8)

Berkenhoff & Drebes GmbH
Germany
Address

6334 Asslar
Cincinnati Milacron
United Kingdom
Address
Kingsbury Road
B24 0QU Birmingham
Ford Werke AG
Germany
Address

53001 Köln
Lumonics Ltd
United Kingdom
Address
Losford Lane
CV21 1QN Rugby
Peugeot SA
France
Address
75 Avenue De La Grande Armée
75116 Paris
Robotiker
Spain
Address
Barrio Belako
48100 Munguia
SIEMENS AG
Germany
Address
Wittelsbacherplatz
80333 Muenchen
Weidmuller GmbH
Austria
Address

7570 Baden