Wherever error prevention is paramount, the Local Positioning System from Sarissa guarantees that production processes run smoothly. The PositionBox position detection system ensures that assembly processes always run smoothly - even if they require a high level of concentration from production staff. In the BMW Group's engine manufacturing plant, bearing shells of different thicknesses are used for optimum crankshaft mounting, but these are difficult to distinguish visually. The Sarissa assistance system therefore ensures that the respective bearing shell always finds its correct position. The system thus provides valuable support in the error-free assembly process.

The intelligent 3D coordinate sensor PositionBox determines spatial coordinates with millimeter precision for quality assurance and provides reliable feedback in real time. Errors can therefore be avoided. All applications in which the correct position of an individual part needs to be determined can thus be smoothly safeguarded. This functionality has been in use at the BMW Group's engine manufacturing plant in Munich since 2017.

The BMW engines for the small series are built in the engine manufactory in Munich on mobile workpiece carriers. In order to guarantee perfect bearing arrangements for the six- and twelve-cylinder crankshafts, suitably matched bearing shells must be installed on each bearing bracket. This requires an exact measurement of the respective bearing bracket before the bearing shells are installed. This data can be used to determine the appropriate bearing shells with the correct thickness for the respective position in the bearing bracket. This is where the position detection system comes in. Although the bearing shells are different, it is almost impossible for production staff to distinguish them visually and they are therefore easy to confuse. The aim is to prevent this with an error prevention system during value creation.

Confusion excluded

The Local Positioning System is a solution that ensures accuracy and saves costs by preventing deviations in production. Because the accuracy and precision of the system are in the millimeter range, it is suitable for applications with hand-held tools of all kinds. The position detection system is independent of light sources and audible sound. The ultra-sound signals emitted by the system are physiologically harmless. Sarissa has already worked successfully with the BMW Group on safeguarding processes using the position detection system. Sarissa developed a specific solution for bearing shell assembly at BMW in Munich. In this application, Sarissa's software determines the coordinates of the bearing shell rather than the coordinates of the tool tip, as is usually the case. An invisible "tube" between the code reader with position transmitter and the QR code on the bearing shell makes it possible for the position data of the bearing shell in the motor to be determined and transmitted to the station controller.

The system provides support in selecting the correct bearing shell and as a final check after assembly. This ensures zero-defect production that meets high quality standards and prevents mix-ups. The PositionBox receives the motor type currently in the assembly station and the bearing classifications to be installed for each bearing bracket from the PLC. The production employees can then see which bearing shells are required for the specific motor type on the screen using a visualization.

The employees in production place the bearing shells with a DataMatrix code in the designated positions in the storage rack. In the special application at the BMW Group, a code reader is used to which a Sarissa position transmitter has been attached. The production employees scan the DataMatrix code printed on the storage tray with the code reader. The code reader's position transmitter then sends high-frequency ultrasonic signals into the room, which are picked up by an ultrasonic receiver. Using the QR code and after communicating with the PLC, the PositionBox determines in real time whether the correct bearing shell is in the specified mounting position. Although the tool transmitter is located on the code reader, the software always determines the XYZ position of the QR code and therefore of the bearing shell and not the position of the code reader. It is irrelevant whether the code reader is held at different angles or by a right or left-handed person during the reading process. A virtual pointer of any adjustable length with a fictitious code reader at its tip is innovative in this design.

Effortless error correction

If a bearing shell is accidentally fitted in the wrong position, the engine block is immediately prevented from leaving the workstation. The error is visualized on the screen and the employees can correct the work step independently. After the correction, the software confirms on the screen that all bearing shells have finally been fitted correctly. The easy-to-use PositionBox user software effectively prevents any possible incorrect action in terms of poka-yoke. The intelligent sensor technology of the PositionBox therefore makes a major contribution to production quality.