The fine seam sealing in the automotive industry is one of many industrial applications which are not running fully automated yet. Up to now, narrow tolerances of mechanical parts have required an individual inspection and treatment. Now a new generation of position detection set out to solve this problem.

A typical robot-aided application cell sets forth certain requirements for the processing of mechanical parts, such as part positioning, tolerances, and integrity. Correcting the robot path program by means of preset object position recognition is today state-of-the-art, but for many applications a single position correction of the robot path is not sufficient, however. New, additional technological means are required for accurate information about the contour curve of these parts.
VMT has, in close cooperation with clients, developed a new generation of position identification. The core of the solution is the Pepperl+Fuchs LineRunner which is based on the laser triangulation method and offers significant benefits. Thus with its compact design, the sensor can be installed on the robot easily. Furthermore, stud holes ensure the sensor replacement in a simple way whereby the sensor re-calibration is not required. As measuring laser an infrared laser diode is used which reacts robustly to ambient light interferences. The laser technology provides together with an intelligent lighting control reliable results also on diverse surfaces. A further advantage of the LineRunner is that no video signal wiring on the robot is necessary.

Optimal and Individual Robot Paths
The VMT BK (Bahn-Korrektur aka path correction) system covers the entire contour of the part. Moving along the part by means of the robot, the system registers the 3D position of every point of the part's contour along the path. With the aid of these coordinates, it is possible to correct the entire contour curve along the robot path. The result is an optimal and part-specific robot path, thus also a very accurately adjusted application.
All measuring points can be liberally edited. i.e., the position of individual measuring points can be manually shifted using an entry mask, the coordinates can be provided with offsets, and measuring points can be added or removed. The measuring points of application paths can be liberally allocated. Thus, the measuring results have influence on each individual application point of the robot path.

Robot Integration
An important advantage of the VMT systems is their easy operation and programming - this applies also to the VMT BK system. Completely integrated in the user interface, the system features the same operation philosophy as all other VMT machine vision solutions. The combination with standard position recognition and/or inspection tasks is possible, as the VMT BK software can be installed on the same hardware platform.
For simple integration of this technology in the robot, there is yet another supplementary module in the VMT BK system's software where all data exchanges are parameterized. These drivers are available for most robot-controlled systems deployed in the automobile industry (Kuka, ABB, Dürr, and Fanuc).

Field Test in Automotive Production
The contour-based path correction has meanwhile proven successfully its value with several automobile makers in various applications. For instance, in clinch flange sealing on vehicle doors and flaps, the clinch flange that joins the inner door panel with the outer door panel is sealed with PVC. The PVC-sealing of the seam is fully automated, using a robot and a suitable application technology. The quality standard for PVC-sealed seams is very high, because perfect sealing is important also from the "cosmetic" perspective. These seams are visible to the end customer and must therefore have an even appearance.
In order to be able to satisfy these requirements, the robot-controlled LineRunner sensor has to move along the door contour continually, without halting at the measuring points. This facilitates accurate copying of the door contour and of the position in space. Upon receiving this information, the robot is capable of adjusting to the given vehicle's door and performing its application run.

Gap Measurement for Collision Prevention
Since the application is performed with the door closed and the seams to be sealed are situated on the inner side of the door, the robot is fitted with a special hook application nozzle. The nozzle runs through the gap around the door. Typical diameter of the nozzle is 2.5 mm, whereby the gap is between 3 and 4 mm wide - depending on vehicle model. Since doors vary in their assembly position due to body shell tolerances, the gap may vary, too. This increases the risk of a collision of the application nozzle and the body. Such a collision would make the application nozzle useless. By extension, this would lead to machine-down time and loss of production.
In order to prevent such losses, the VMT BK System tests also the gap width during the measuring run. If the system finds that the gap is not sufficiently wide, the robot's application run is not permitted. Information on the different application tools stored in the system facilitates monitoring of collision danger also with different tools. This mode of operation is an important contribution to the overall plant availability.

Automated Sewing Tool
Another example of the VMT BK System's usability is taken from the automobile supplier industry. For the sake of visual betterment of vehicle cockpits, the robot applies artistic seams. Since such seams are within the vehicle crew's immediate sight range, an optically correct impression is very important. For this purpose, the VMT BK System defines the optimal application path for the robot: The path of a crimp situated on the cockpit is detected by the VMT BK system, and the robot's seaming tool is guided along this path with an accuracy of +/- 0.2 mm. Laser-based technology makes it possible to perform this application without a problem also on cockpits of different colors.