High speed tracking system for laser cutting

Citation

(1999), "High speed tracking system for laser cutting", Industrial Robot, Vol. 26 No. 1. https://doi.org/10.1108/ir.1999.04926aaf.004

High speed tracking system for laser cutting

High speed tracking system for laser cutting

Keywords Cutting lasers, Laser welding, Meta Technology

For laser welding applications Didcot-based Meta Technology has developed a high speed version of its vision seam tracking system.

To handle the high welding speeds encountered when laser welding, the maximum tracking speed has been increased from 4m/min for the standard MTX pc to 8m/min for MTX pc-HS.

The increased speed has been achieved while also improving tracking accuracy to within 0.1mm. This was essential to meet the demanding requirements of laser welding.

The principle of operation remains the same as conventional weld tracking. A sensor in front of the laser welding head projects a laser stripe over and at 90° to the joint. This is generated by a laser diode that operates in a different part of the spectrum to a CO₂ laser welding machine (see Plate 3).

Plate 3 The sensor is mounted in front of the pressure wheel with the laser mirror system to its left

A camera within the 100 × 40 × 60mm sensor head views the stripe and can detect the joint. Software within the control system interprets the image and translates this into correction signals.

The high speed tracking system was initially developed in conjunction with KUKA Schweissanlagen GmbH to be used on its integrated robot-laser welding system.

To achieve satisfactory laser welding, pressure is required on the top sheet to ensure good contact between the two surfaces. The KUKA solution was to incorporate a wheel into the robot end-of-arm tooling to guarantee the necessary contact between the parts being joined.

This approach has the advantage that the wheel mechanism also ensures the correct height above the joint, while the tracking system is confined to keeping the laser centrally positioned over the joint. However, it does mean that the path corrections cannot be provided via the robot. This would cause the contact wheel to drag across the metal surface.

KUKA developed a novel solution that incorporated a slide at the end of the robot arm. This moves at 90° to the joint path. The slide carries the laser mirror and the final output optics as well as the Meta sensor. Corrections via the slide keep the torch in the right position without deviating the robot arm from the programmed path.

The first system was ordered in February; already four have been installed.

One is in a Spanish automotive company where they are used for roof-seam welding at the roof-body side joint. Another is in a development laboratory of a German automotive company and the final system in a university in Dresden.

Early trials suggest the high speed tracking system can also be applied to producing "tailored blanks". These are constructed of sheets of different thickness welded together so that maximum thickness occurs in areas of maximum stress.

Laser welding demands precise position and the new high speed tracking system has proved ideal for compensation for inaccuracies in components or positioning in the fixtures.

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