To avoid the need to re-teach robot programs generated off-line, it is necessary to achieve an absolutely accurate calibration of the robots and to obtain exact tool and frame data.
On the production line, two Fanuc R2000iB/165 robots are used on a linear axis for spot welding. The cell also has a gun rack so that tool changes can be carried out. Car body panels are put together in the cell and welded by the robot. The cell itself is of universal configuration so that in future it will be possible to produce a wide range of different parts by changing the jigs and loading new robot programs generated off-line.
The task was to automate manual workstations over the Christmas period by setting up the cell. As there were only two weeks available to commission the entire system, the cell had to be programmed off-line first so that it could then be transferred directly to production. To reduce to a minimum the need to re-teach the robot programs generated off-line, it was necessary to achieve an absolutely accurate calibration of the robots and to obtain exact tool and frame data.
The robots and the linear axis were measured with absolute accuracy using the loop:in software. For the remaining cell measurements, a universal master was manufactured which can be held by any jig. The ball positions were measured with a FARO measuring arm in relation to the car frame. These data were then used by LaserLAB and tool:in to determine the transformation from the jig (car frame) and the system robot/linear axis.
The re-teach time of the programs generated off-line was minimised. It was also possible to achieve the objective of a very short commissioning time.
In addition to this, the measurement revealed that the switching cabinets of the two robots had been mixed up and so the master data of the two robots would have been incorrect. A fatal error that would not have been discovered without a calibration. The robots can be automatically mastered at any time in the future.