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Siemens: Flexible transmission assembly

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For the installation of the new assembly line, the transmission manufacturer ZF in Friedrichshafen, Germany, needed an automation concept that would take the modular set-up of the plant into account. With integrated Simatic hardware and the new TIA Portal, it was possible to meet the transmission manufacturer’s rigorous requirements concerning the line‘s fail-safety, productivity, and availability.

ZF Friedrichshafen AG is one of the leading automotive supplier companies worldwide in driveline and chassis technology with 121 production companies in 27 countries. The tasks of modern truck transmissions today go way beyond mere power transmission: they also make sure that commercial vehicles are eco-friendly, economic, silent, and comfortable. With TraXon, ZF Friedrichshafen AG developed an automatic transmission system for heavy trucks that lives up to current and future needs and is ready to go into production. It is based on a compact basic transmission and a fl exible modular concept. The TraXon basic transmission can be combined with fi ve modules: single- or dual-disc clutch, dual-clutch module, hybrid module, motor-dependent power take-off module, and torque converter clutch module.

Recently, a new mixed assembly line was put into service in factory 2 in Friedrichshafen to expand the capacity and to implement the new technology required for the TraXon series. The U-shaped conveyor line consists of the main conveyor comprising 34 interlinked conveyor line assembly stations and directly linked preassembly and commissioning areas as well For the installation of the new assembly line, the transmission manufacturer ZF in Friedrichshafen, Germany, needed an automation concept that would take the modular set-up of the plant into account. With integrated Simatic hardware and the new TIA Portal, it was possible to meet the transmission manufacturer’s rigorous requirements concerning the line‘s fail-safety, productivity, and availability.Flexible transmission assemblyas comprehensive tests in the process. The output can be fl exibly clocked between two and eight minutes, depending on customer requirements. Two transmission series are assembled on the new line in 500 different parts-list variations – made to order in batch sizes of one.

Comprehensive requirements

“Our main requirements on the new line were ergonomic design according to the latest ergonomic  fi ndings, a consistent zero-fault strategy in the process, and high output fl exibility without productivity losses. In addition, the utilization rate was to be above 90% and the plant availability above 96%,” explains Rafael Kraja, assembly production planner at ZF.

Rafael Kraja, assembly production planner at ZF.In order to achieve the required optimal ergonomic conditions for the workers, the assembly trolley automatically brings the transmissions to be assembled into the best position for the respective processing step. There is also worker support, including a monitor at every workstation breaking down the task into exactly described and graphically displayed steps. ZF achieves a zero-fault strategy in the  assembly process  by continuously monitoring 100% of all quality-relevant operating processes and material withdrawals in the entire assembly at every workstation and at every step. In addition, the higher IT control system documents which processes were carried out – from torque monitoring, to poka-yoke signals, to material withdrawals. At the end of the assembly line, the assembled transmission is then subjected to a function test and a leak test. The system allows delivery of a transmission only if all the quality features are confi rmed and documented as OK.

Use of proven hardware

Because of the overall positive experience, the production equipment designers at ZF chose automation technology by Siemens for the implementation. In consultation with the manufacturer of the conveyer drive, the Kirchner Solutions GmbH and its electronic partner Graf Automation GmbH, they decided on a Simatic S7-317 PN as the line control in combination with Simatic ET 200S controllers in the assembly trolleys as well as in the workstations and the picking shelves. A total of 120 Simatic ET 200S controllers were installed. Since every assembly trolley is connected to a common emergency stop cycle, fail-safe interface modules are also being used. The communication to the assembly trolleys takes places wirelessly via Profi net with the Profi safe profi le. For this, a radiating cable was installed in the support rails. The workstation PLCs are connected via Industrial Ethernet cables.The project team selected Simatic fl at-panel monitors with all-round IP65 protection as monitors at the assembly stations. They are actuated by several Microbox Simatic IPC427C located in the PLC control cabinets below the ceiling. The web browsers on the PCs can be used for diagnostic purposes in order to access the web servers available on all controllers and thus display the diagnostics data of each CPU on each monitor. This continuity contributes to increased availability – without additional programming effort. A higher control system manages all the order data and parts lists.

Innovative engineering with TIA Portal

In order to effectively realize the modular, local concept, ZF needed a modern engineering system. The  new TIA Portal engineering framework was used for the fi rst time for confi guring a project of this magnitude. Ralf Klews, production equipment designer in electrical engineering, was able to use the support of Siemens in Stuttgart and is convinced that the new solution will serve as a model for other similar projects currently being planned. The global or project- wide storage of library projects or modules is particularly helpful in modular projects of this magnitude. The master templates for hardware confi gurations are also useful in this context. Klews estimates a quite realistic savings potential of about 30 % in the new assembly line. Attilo Graf, working at Graf Automation GmbH, agrees: “I am looking forward to using TIA Portal V12 in the future, since the confi guration of the Sinamics G120 drives used here will be integrated as well. And with Simatic ET 200SP, we will have the space reserves in the control cabinet we have always wanted.

Convincing solution

Günther Stauber, project and assembly manager at ZF, considers the company’s requirements to have been optimally met by the new system: “The new assembly line corresponds to the latest ergonomic fi ndings – even the employees and the work council praise the excellent ergonomics; in addition, it is a logically consistent expansion of proven principles of the ZF production system, such as just-in-time manufacturing, zero faults, standardization, fl exibility, and employee focus.” Klews and Graf agree that the local design, safe communication via Profi safe, and, last but not least, TIA Portal with its possibilities are the keys to this success

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