Operation of the SmartTurn index table at the Mercedes Benz plant in Ludwigsfelde

Rotary tables with defined indexing are widely known in the automotive industry. In the past, rotary tables were deactivated by means of cam lobes and mechanic end switches or initiators. The motor is controlled via SPC. The variety of relevantly re-quired switches is subject to the design of the index table and the application, they therefore need an adequate amount of space and thus form an interfering edge in the operation of turntables. The cam lobes and end switches are often surrounded by installed tools and, as a consequence, difficult to access, making adjustment and maintenance work complicated. Cycle time and fluctuations in the running time lead to positioning variation of the rotary table due to the signal processing of the end switches by the SPC.

Expert-Tünkers have now developed an entirely new concept for index table control in collaboration with Pepperl+Fuchs, which renders end switches and cam lobes ob-solete. This development resulted in the design of the intelligent SmartTurn index table control. The concept consists of an inductive sensor and an evaluation unit. The functionality of the rotary table is based on a set program; only 2 switches have to be adjusted in correspondence with the design and relevant application. There is no longer a need for complex adjustments of the cam lobes and the switch-off posi-tion is continuously adjusted ensuring that the index table stops optimally in initial position. Thus, the start-up of the rotary table only takes up a fraction of the usual time. The motor is directly switched off without SPC rerouting. The SPC receives in-formation as to initial position and any disturbance. An interface allows for detailed analysis of statistic data and disturbances. The control is suitable for rotary tables of any size. Optional position sensors and transponder technology complete the sys-tem. These are available with or without safety function.

SmartTurn was initially operated at a production plant. The existent end switches of the rotary table at station 1208, assembly group side member NCV3, were removed and replaced by the SmartTurn system at the Mercedes Benz plant in Ludwigsfelde on 2 August 2008. Since then the SmartTurn unit reliably controls the index table. As the rotary table was retrofitted, modifications of the electric installation, the SPC pro-gram and the mechanical connection of the sensor became necessary. Due to the fact that sensor and evaluation unit are pluggable, retrofitting was completed within a short time. The following start-up proved to be child’s play, as expected. Two forward and to backward turns in manual operation mode: done. The index table was ready to resume operation. In the next step, the two tool position sensors were installed.

Mercedes Benz were more than satisfied with the retrofit. A proper innovative, opti-mally adjusted solution for a rotary table with set indexing. Easy integration into the entire installation, strongly reduced start-up time, minimised interference contours, enhanced plant availability and the diagnostic facility form only the most distinctive advantages of the SmartTurn index table control, which convinced immediately.

Thus, it is only logic that Mercedes Benz in Ludwigsfelde are now planning to retrofit other index tables and bank on SmartTurn for future projects.

Pictures of field report (PDF, 217 KB)