Liebherr-Verzahntechnik has been manufacturing gear cutting machines and automation systems for seven decades. However, the increasing individualization of the machines, the ever smaller batch sizes and the shortest possible throughput times presented Liebherr with major challenges. Under the premise of process reliability, the Kempten-based company has therefore implemented consistent digitalization and automation and is facing up to the competition with quality and flexibility.

Liebherr has been supplying turnkey production cells and lines since the 1970s. And the company's own production is also highly automated. "Flexibility and automation go hand in hand," says Matthias Dodel, CAM programmer and system supervisor for production lines at Liebherr. As small series up to batch size 1 with a large part variance are manufactured in Kempten, automation is achieved using a pallet handling system, among other things. The component to be processed is clamped onto a uniform carrier plate by an operator outside the machine and temporarily stored in the integrated high-bay warehouse until it is processed. When the master computer issues the order for processing, the carrier plate with the component is transferred to the processing center by the rack vehicle and then picked up again. All travel and storage/retrieval movements are carried out in unmanned automatic mode. The Soflex PCS (Production Control Software) ensures a long service life. It controls the entire production process and plans the entire sequence on the basis of data from the ERP system. In conjunction with the TDM tool management system, this enables "highly flexible, reliable and efficient production around the clock," says Dodel.

Replacement of outdated software solutions

With the decision for an automated milling and turning center, the systems involved were also put to the test and the entire process chain was reconsidered. In particular, the tool management system previously used was no longer suitable for the new challenges: "It was a proprietary stand-alone solution that was tailored to our previous CAM software and therefore not compatible with the new solution." Adapting it accordingly would have been very time-consuming and costly. "Because the interfaces were missing, continuing to use the software would have been a constant challenge for us," says Dodel.

Predictive tool provision at the machine. © Liebherr/TDM

Liebherr was therefore looking for a solution partner "for whom there are no technical limits in the interfaces to all possible applications in production". Because they repeatedly encountered highly satisfied TDM users during their reference visits to numerous CAM manufacturers, Liebherr opted for the tool management solution from TDM Systems in 2018. "TDM is a software that offers us all the freedom we need thanks to its variety of interfaces and enables us to implement our digitalization concept efficiently," says Dodel, summarizing the management decision. This decision also secures Liebherr's investments in the long term - because the neutrality and openness of the TDM system means that they are not tied to specific software providers in production.

Error rate zero

The implementation of the software was problem-free and the data transfer also ran as desired. "The elimination of manual data entry reduced the error rate to zero," says Dodel. Liebherr uses TDM not only for traditional tool management, but also as a document management system for CAM documents, NC programs and set-up instructions. All tool and fixture requirements for the machining centers are handled by the storage and fixture management system. The interfaces to the Esprit CAM system, Soflex production control system and Zoller presetting system enable automated data flow.

For small batches up to batch size 1, NC programming quickly becomes a bottleneck in production. If you cannot or do not want to hire additional employees, you have to rely on optimizing your processes. Liebherr created around 5,000 NC programs within four years with the same team - despite expanding its machine park. "That would have taken us ten years in the past," says Dodel happily. At the same time, this team digitized the tool inventory, i.e. set up the entire tool database and also took over further data maintenance. The fact that the NC programmers are so efficient thanks to TDM is due to the modules for data and graphics generation as well as the CAM interface from TDM-Esprit. This is because the permanently defined complete tools are consistent and can therefore also be used as digital twins for simulation.

Presetting based on data from TDM

3,800 complete tools and 7,000 fixtures are managed at Liebherr. When the production control system plans an order, the complete tools required are determined and the demand is compared with the tools available on the machines and the respective tool life. If tools are missing, they are assembled, preset and measured using a requirements list from Soflex. The presetting also works with data from TDM and automatically accesses the created target data. The tools are changed fully automatically if required. "Without TDM, it would not be possible to keep track of 3,800 complete tools and deliver them to the machine at the right time and in consistent quality. Without the software, tool supply would simply not be possible and automation would not be possible," emphasizes Dodel. "In summary, we can say that we always work with process-reliable data thanks to the automated data transfer from and to the TDM software," says Dodel.