15 May 2013
Dual-laser approach uses green and infrared wavelengths to weld copper parts.
By Matthew Peach in Munich
Conference chairman Rüdiger Brockmann of Trumpf told the gathering, "Laser processes are becoming more and more common in automotive production. The many possibilities of automation in manufacture and testing, and the wide variety of manufacturing techniques combined with decreasing production costs are the most important enablers for the successful application of laser technology.
"Today, laser applications can be found in the areas of powertrain, electro-mobility, press shop, body shop and assembly. This panel presents the latest applications and developments of automotive related laser technologies. In addition, future opportunities to realize production with increased efficiency both in terms of cost and energy, will be demonstrated."
First on stage, Abels commented, "Laser welding is a promising joining process for copper - such as in the case of electrical car battery contacts in vehicles. As part of ongoing research projects, the monitoring of copper laser-welds for quality assurance and novel approaches to processing devices like laser welding heads. The work also has potential in the area of industrial image processing-based quality assurance systems for spot welding of IC pins."
The research leading to these dual laser welding discoveries is receiving funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 260153 (QCOALA: Quality Control for Aluminium Laser-Welded Assemblies).
The laser process uses pulsed solid state laser delivering a pulsed energy of 20-30J with a pulse length of 10-15ms. Possible weld defects to avoid include misalignment between pin and carrier, misalignment of the laser spot to pin edge; and incorrect weld size.
Abels concluded, "We have achieved first results of basic investigation for process monitoring of copper welding for bettery application. And industrial high volume automatic process monitoring system of IC pin welding in automotive engine sensor fabrication."Precitec considered "Approaches for quality assurance and dual wavelength processing for laser cutting of copper".
Precitec has developed a concept for a dual wavelength processor with wavelengths of green and infrared radiation. Kogel-Hollacher explained to optics.org, “The green light treats the copper first to initiate the welding because it is absorbed at a rate eight times that of the infrared, which is better absorbed once the green light has started the welding process. An important issue to resolve is the superimposition of the laser spots for effective precision welding."
"For simultaneous laser processing with infrared and SHG (second harmonic generation) green laser light, an industrial device has been developed by Precitec and tested on several copper alloys. The applied laser power was the maximum available for SHG (green) emission in CW format. The experiences of monitoring laser processes with only an IR laser was transferred to the sensor configuration for the SHG path. This device will be further tested for forthcoming projects."
QCOALA is a FP7 European funded project within Theme 3 - Information and Communication Technologies. This project is a collaboration between EU companies and research organisations, with the objective of developing a new dual-wavelength laser processing system for welding thin-gauge aluminium and copper, 0.1mm to 1.0mm in thickness, with integrated process monitoring and in-line non-destructive inspection, and establishing its capability to provide a reliable, high-speed, low-cost and high-quality joining solution for electric car battery and thin-film photovoltaic (PV) cell interconnections.
Oliver Müllerschön from Trumpf Laser who spoke about diverse laser applications in materials processing the automotive industry: “The Laser helps to create flexible processes and makes them faster or makes applications possible that cannot be done with conventional methods.
"The making of hot forming parts for lightweight construction, surface treatments with short pulse lasers as welding or bonding pre-operations and remote welding technology are some of the more interesting applications.”
He said, “When laser welding of galvanized sheets the evacuation of air needs to be undertaken to produce a good weld quality.” He also considered remote laser welding, commenting, “for reasons of economy, remote laser welding could replace the current practice of resistance spot welding.”
“A new kind of laser welding technology is being implemented - remote stir welding will bridge large gaps in some automotive laser applications and could even replace MAG welding. By using a laser welding gun, Volkswagen is for the first time emplying a completely new concept in laser welding. In this case, not only the strength of the welded areas is increased, but also the number of joints can be reduced.”
FlexLine is a modular system for turning, milling, welding, heat treatment, hard turning, honing and grinding, including parts tracking, labeling and work piece handling in one piece flow.
Finally, Niclas Palmquist, Manufacturing Engineering, Volvo Car Corporation, gave an interesting presentation on assessing quality assurance aspects of laser welds.
About the Author
Matthew Peach is a contributing editor to optics.org.