Meta opens door to laser based seam welding in auto industry

Citation

(1999), "Meta opens door to laser based seam welding in auto industry", Industrial Robot, Vol. 26 No. 2. https://doi.org/10.1108/ir.1999.04926baf.007

Meta opens door to laser based seam welding in auto industry

Meta opens door to laser based seam welding in auto industry

Keywords Meta Technology, Welding

Spot welding is almost universally used to assemble automotive bodies primarily because it requires the least positional accuracy; usually within 5mm is sufficient of the three major alternatives. The other options are arc or laser welding. Arc welding requires an accuracy of 0.5mm while laser welding has even more stringent demands of within 0.1mm.

Typical linear speed when spot welding is three spots/sec at 50mm centres which is about 9m/min of weld. On paper laser welding offers dramatic productivity increases with operating speeds up to 20m/min. Laser welding also promises improved quality coupled with increases in overall stiffness of completed assembly.

To date it has been difficult to exploit the benefits of laser welding because cumulative tolerances between components and fixtures can not guarantee that the joint is positioned within the required 0.1mm.

Laser welding is usually carried out through the top sheet using a lap joint or a flange. Because of the difficulty of precisely positioning the weld, it is common practice to weld away from the edge, then apply sealant. This has the obvious disadvantage of adding an extra operation with all the incumbent costs.

To address this problem, Didcot based Meta Technology has introduced a seam tracking system which achieves the desired accuracy of 0.1mm. This allows the weld to be along the edge joint, thereby eliminating the sealing operation. Removing the sealing operation, transforms the economics of laser welding.

Add to that a number of technological breakthroughs that address other problem areas associated with laser welding, then its not unreasonable to predict that the time is ripe for serious re-assessment of laser welding. One major hurdle to be overcome for cost effective laser welding can be summarised as "create optimum joint conditions".

A laser joint demands that the two surfaces to be welded are held tightly together. KUKA has developed some end of arm tooling for their robots that neatly resolves that particular problem.

A pressure wheel is mounted at the end of the robot arm that maintains sufficient pressure between the two sheets to ensure a proper joint is achieved. This follows the programmed path of the weld. A combination of mirrors and telescopic tubes allows the laser beam to be orientated by the robot.

Using the robot to maintain pressure for the joint means it cannot also adjust for tracking position. This has been resolved using the KUKA telescopic laser delivery system. A small slide at 90° to the direction of travel adjusts the weld position based on corrections from the Meta tracking system. This guarantees that the laser beam is delivered at the edge to within 0.1mm.

The door is open now for high volume laser welding in the automotive industry at speeds up to 20m per minute compared with around 9m/min for spot welding. That's enough of a productivity increase to even keep George Brown happy.

Contact: Mike Wilson, Managing Director, Meta Technology Limited, 10 Harrier Park, Southmead Industrial Estate, Didcot, Oxon, OX11 7PL. Tel: +44 (0)1235 512215; Fax: +44 (0)1235 512115.