Seam sealing and undercoating

Automotive engineering Underbody protection

When worn parts are replaced, the robot programs need to undergo re-teaching

Seam sealing and undercoating

Cell description

The customer has a production line in the paint shop where PVC is applied to the underside of car bodies as a sealant. The cell contains 12 KUKA KR16 robots on linear axes, equipped with SCA Schucker spray lances, each with three nozzles. In the seam sealing line there are four old Kuka KR 6 robots that can only be adjusted by Nonius.

Task definition

The spray lances are subject to wear and are therefore replaced at regular intervals. Changing the tools means that the robot programs are no longer exact and need to undergo re-teaching.

The customer also wants to do more off-line programming of the robots in future and needs absolutely accurate robots for this. The existing robots, however, can no longer be measured with absolute accuracy by the manufacturer because of their age.


The measuring triangle was used to measure the nozzles. With a suitable adaptation it was mounted on the lance instead of the nozzle with two screws. The measuring triangle has the advantage that it determines not only the direction of impact of the tool, i.e. the jet direction of the PVC, but also the tool's X-direction which plays a part with flatstream in contrast to round spray.

For the measurement of the robots with loop:in, the linear axes were also taken into consideration. The linear axis was followed while the robot kept its TCP in the LaserLAB. The results of the calibration also showed up, among other things, the assembly fault of the robot on the linear axis.

Customer benefit

Problems arising from the replacement of a spray lance have been eliminated completely as only the three tools need to be re-measured each time. This only takes 20-30 minutes.

Moreover, the robots were measured absolutely accurately with loop:in. This gives the customer the option of off-line programming.

The problems that arose in the past with the old KR6 robots have been resolved for good. Once a point shift is diagnosed, the robot is measured with loop:in and then the tools with tool:in. Point shifts are therefore eliminated.