Laser sensor cuts non-productive time at Volkswagen plant

Citation

(1998), "Laser sensor cuts non-productive time at Volkswagen plant", Sensor Review, Vol. 18 No. 2. https://doi.org/10.1108/sr.1998.08718baf.001

Laser sensor cuts non-productive time at Volkswagen plant

Laser sensor cuts non-productive time at Volkswagen plant

Keywords Distance measurement, IGM, Laser sensors

The very latest in laser distance sensing has been incorporated into an IGM multi-headed robotic welding solution supplied to the Volkswagen plant in Brussels for the production of the new Golf IV motor vehicle.

Called ELS, the laser sensor has been specifically designed to detect the exact position and condition of thin overlap or bull welded seams (Plate 1). A considerable reduction in non-productive search times is claimed for this equipment over conventional tactile sensors, because simultaneous detection of both height and lateral position are undertaken at high speeds. Although ideal for use in the automotive industry, it would also have many other metal fabrication applications within industries where weld accuracy and final product quality are paramount, working on similarly difficult to detect thin materials to a minimum thickness of 0.65mm.

The ELS sensor is set up to search for edges and gaps typically on workpieces with overlapping or butt welded seams. Deviations are also detected between the actual and original workpiece positions, with appropriate correctional action taken by the program after a search run or runs by the robot. All re-positioning is done in 3D mode, with both linear and height changes being accommodated within a single search drive per position. weld gaps and the height of overlap seams are also detected with the welding parameters automatically adjusted to suit. This device is also fitted with automatically operated protective shutters to further protect the laser device from smoke and weld spatters during operation.

Plate 1 The latest ELS laser distance sensor from IGM Robotic Systems Ltd for use with automatic welding machines

The laser sensor can be mounted in seven different positions on the robot torch for maximum accessibility. Absolute computation of the space co-ordinates of any welded seam position is provided during a search procedure, even though the angles for the initial search and final welding may be entirely different. Image analysis is undertaken after each search run, to ensure that spurious results from defects such as edge crack reflections, spatter beads or dirt can be filtered out.

The sensing speed determines the sampling frequency which can be up to 20 readings per millimetre, giving a resolution of 0.05mm For a perfect seam recognition, the seam type is first allocated to the respective search run. The absolute position of a detected point on the welded seam as determined by the sensor is transferred to the control system for interpolation within the parameters permitted by the robot.

An operating panel with clearly arranged and fully defined keys ensures easy programming. The image evaluation software runs under Windows 95 and allows for various measurement and searching runs to cover changing workpiece parameters.

For further information contact: IGM Robotic Systems Ltd, Unit 18/20, Avon Business Park, Wolverhampton Road, Cannock, Staffordshire WS11 1LT. Tel: +44 (0) 01543 462931; Fax: +44 (0) 01543 462836