Space Frame Joining Techniques - Laser Welding

YAG laser systems are increasingly broadening the scope of their industrial application in the automotive industry. Laser welding has a number of inherent advantages over arc-welding which makes the process worthy of consideration for spaceframe applications: -

• Very little thermal distortion
• High processing speeds
• High quality welds
• Conducive to automation – in particular being able to transmit a beam along a fibre optic cable.

It cannot be ignored however that, as to be expected, there are limitations associated with the process as well. These are as follows: -

• Relative expense of capital equipment is very high.
• Process suffers from limited penetration depths which may restrict the use of lasers in some areas.
• The process can experience crack sensitivity problems – sometimes compensated for by the introduction of filler wires high in silicon.
• Highly focussed beam makes the process intolerant to gaps in joints.
• Risks to operators in terms of potential eye damage means stringent safety precautions need to be adopted.

Despite these limitations, the prominence of laser welding in the automobile industry is growing. This is generally because of the superior quality of the weld finish, potential material savings and the flexibility the process offers particularly with respect to new designs and the use of the optical fibre beam delivery system.

Ref. Barnes T, Pashby I, (1998)

Audi have taken the laser welding process a stage further and developed a laser/MIG hybrid welding process. They believe this achieves diverse synergy effects by combing both processes in order to extend the limits of current thermal jointing processes, that is in terms of efficiency, seam quality and process reliability. The hybrid process is used to weld various functional panels onto the lateral roof frame with seam length runs up to 4.5m.

Ref. Youson M (2002)

There are several other welding techniques that could be considered and discussed for automobile manufacture and in particular with respect to aluminium materials. Spot welding and laser welding are the dominant techniques in the industry but there is evidence that hybrid techniques such as the laser/MIG are in development. This suggests that the suitability of laser welding technology, without further innovation in the process to support the manufacture of aluminium bodies, cannot be a foregone conclusion.