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Perfectly Positioning Individual Parts

Wherever error prevention is the top priority, the Local Positioning System from Sarissa guarantees that manufacturing processes run smoothly. The PositionBox position detection system ensures that assembly processes always run smoothly – even if they always demand a very high level of concentration from the production staff. In the BMW Group’s engine manufacturing facility, bearing shells of different thicknesses are used for optimum crankshaft bearing support, but the shells are difficult to differentiate visually. The Sarissa system therefore 100% ensures that the respective bearing shell always finds its correct position. The assistance system from Sarissa thus provides valuable support in the error-free assembly process.

The intelligent 3D coordinate sensor PositionBox determines spatial coordinates with millimeter accuracy for quality assurance and provides reliable feedback in real time. Errors are thus avoided before they happen. All applications in which the correct position of an individual part is to be determined can thus be secured smoothly. This mode of operation has been used successfully in the engine manufacturing facility at the BMW Group in Munich since 2017.

The BMW engines for small series vehicles are built on mobile workpiece carriers in the engine factory in Munich. In order to be able to ensure 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. Based on this data, the appropriate bearing shells with the correct thickness can be determined for the respective location in the bearing bracket.

This is precisely where the Sarissa position recognition system comes into its own, because although the bearing shells are different, they can be almost indistinguishable visually from one another by production staff and are therefore easily confused. This must be prevented with an error prevention system during value creation.

No More Mix-Ups

The Local Positioning System is a solution that ensures freedom from errors and saves costs by preventing deviations in production. The fact that the accuracy and precision of the system is in the millimeter range makes it suitable for applications with hand-held tools of all kinds. Sarissa’s position detection system is independent of light sources and audible sound. At the same time, the soundless ultrasonic signals emitted by the system are physiologically harmless. Sarissa GmbH has previously worked successfully with the BMW Group on safeguarding processes using the position detection system. For bearing shell assembly at the BMW Group in Munich, Sarissa developed a perfectly suited solution.

The highlight in this application is that Sarissa’s software does not determine the coordinates of the tool tip, as is usually the case, but the coordinates of the bearing shell. 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.

Double Support From Sarissa

The Sarissa system provides double support – in selecting the right bearing shell and as a final check after it has been fitted. This ensures zero-defect production that meets the highest quality standards and eliminates mix-ups. How does this work? The PositionBox receives from the PLC the motor type currently in the assembly station as well as the bearing classifications to be installed for each bearing bracket. The production employees then see on the screen, by way of a visualization, which bearing shells are required for the specific motor type.

The production staff place the bearing shells, which are marked with a DataMatrix code, in the designated positions in the bearing bracket. In the special application at the BMW Group, a code reader is used with a Sarissa position transmitter attached. The production workers scan the DataMatrix code printed on the bearing shell with the code reader. The code reader’s position transmitter then sends high-frequency ultrasonic signals into the room, which are received by a Sarissa ultrasonic receiver. Based on the QR code and after communicating with the PLC, the PositionBox determines in real time whether the correct bearing shell is in the prescribed mounting position. Although the tool transmitter is located on the code reader, Sarissa’s software always determines the XYZ position of the QR code and thus the bearing shell, and not the position of the code reader. It makes no difference whether the code reader is held at different angles during the reading process or by a right- or left-handed person. A virtual pointer of any adjustable length with a fictitious code reader at its tip is highly innovative and unique in this design.

Effortless Correction of Errors

If a bearing shell has been accidentally mounted in the wrong position, the motor block is directly prevented from leaving the workstation. The error is visualized on the screen and the production staff can correct the work step independently. After the correction, the software confirms on the screen that all bearing shells have finally been mounted correctly. Thanks to the easy-to-use PositionBox user software, a possible mishandling in the sense of Poka-Yoke is effectively prevented. The intelligent sensor technology of PositionBox thus makes a significant contribution to manufacturing quality.

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