Millions of people worldwide own keys manufactured by Wilka. No matter how stringent the production requirements, the keys and lock cylinders produced must be flawless. Lock and key products require highly efficient and precise manufacturing technology, capable of compensating for temperature fluctuations of several degrees Celsius – a truly remarkable feat. Aumat and AST chose to use Beckhoff's PC-based control technology to develop a system that meets these demands, ensuring machining accuracy down to the industry-required 0.01 millimeters, while easily achieving customized special-purpose machinery with minimal engineering effort.
Wilm Schadach , Beckhoff Rhein / Ruhr office; Achim Ihlefeld , Technical Director of Aumat Maschinenbau ; Manuel Krümmel , Key Production Manager and Mark Straka , Electrical Maintenance Manager of Wilka Schließtechnik ; and Wilfried Wengenroth, General Manager of AST (from left to right)
For the key industry, and for Wilka Schliestechnik, a German company specializing in key production in Fairbert, the most typical characteristic is the large number of custom production orders received daily. Technical Director Olaf Witte explains, “In a sense, our mass production and single-piece flow production can be perfectly combined. An order may contain 1,000 products of the same type, but each product is different—until a single order for a spare key.” Wilka's production structure is correspondingly flexible, possessing a variety of specialized machine tools jointly developed by Aumat Maschinenbau in Solingen, Germany, and AST, a systems integrator in Wuppertal.
The key blank is machined in sequence, first the longitudinal section, then the key plate notch.
According to Achim Ihlefeld, Technical Director at Aumat, a fundamental requirement for professional machine tools is high precision when machining key blanks: "The maximum key tolerance is within one-hundredth of a millimeter. To reliably meet this tolerance, mechanical engineering must be an order of magnitude better. This requires the shortest possible control cycle time and extremely high-precision servo axes. Both of these can be well achieved using Beckhoff's PC control technology, thus allowing for a corresponding number of servo axes even with many parallel milling cycles." Tim Themann, a software development engineer at AST, added: "The precision requirements are extremely high; even a few degrees of temperature fluctuation can have a significant impact on the machining results. The PC control system controls this impact by continuously monitoring the temperature."
Modernizing the key production line using two independent machine tools.
The Wilka key production line, comprised of two independent specialized machine tools, showcases the advantages of a PC control system. As AST General Manager Wilfried Wengenroth stated, “An existing key-cutting machine used for cutting key blades has been overhauled and equipped with Beckhoff control and drive technology. In addition, a profile milling machine for milling key edges is also controlled by the PC control system. All keys are processed sequentially, first the longitudinal section, then the notch. Finally, all keys are delivered along with their matching locks.” Achim Ihlefeld added, “Wilka uses two Beckhoff controllers, both with a unified user interface, which brings them many benefits; if necessary, even if one machine tool stops operating, the company can continue operating the second machine tool without interruption.”
The cutting machine has 9 servo axes, while the milling machine has 23 servo axes, both controlled by AX5000 servo drives and AM3000 servo motors. The two machines are interconnected and communicate via two gateways programmed in C#. Both run on cabinet-style industrial PCs (C6930) on their respective machines and communicate using ADS and TwinCAT automation software. Additionally, the industrial PCs are responsible for transmitting data to Wilka's central data server. According to Achim Ihlefeld, each milling spindle on the profile milling machine also has its own tool management system: "This way, each of the four milling spindles manages 12 tools, enabling efficient execution of a variety of longitudinal milling operations: from thin master keys to thicker, specialized keys used in specific door lock systems. Typically, this would require hundreds of tools. However, thanks to the tool management system, which intelligently coordinates these operations, we only need 48 tools." Tim Themann added, "Tool management is implemented through TwinCAT NC I, which not only selects the appropriate tool but also cuts the ideal lines. Therefore, you can achieve fine edge grinding between deep, flat milling notches adjacent to each other and prevent the machined key from being improperly inserted into the lock cylinder."
Integrated PC control system: the ideal foundation for Industry 4.0
“Aumat’s specialized machine tools have been using Beckhoff’s PC-based control technology since 2005,” said Wilfried Wengenroth. “We’ve been working with AST since 2004. In this context, EtherCAT is also a significant advantage, especially due to its ability to automatically scan the system, particularly during initial commissioning. Furthermore, EtherCAT allows for quick and easy diagnostics of all bus devices.” Mark Straka, Electrical Maintenance Manager at Wilka, added, “We used to employ a very diverse range of controller brands, and it took us about seven years to gradually adopt Beckhoff controllers exclusively. Besides high computing power, the system’s openness is also crucial for us. We can integrate legacy control technologies without incurring exorbitant costs, and we can easily connect to higher-level enterprise networks. The latter is becoming increasingly important, as it ensures access to the entire production infrastructure layer through a standard network: from order entry to production, all the way to maintenance services.”
The interconnected key production line, jointly designed by Aumat and AST , consists of a key cutting machine and a profile milling machine, enabling high-precision single-piece flow processing of key blanks.
Thus, the ideal prerequisite is the realization of the Industry 4.0 concept. Olaf Witte believes that one key issue cannot be ignored in this regard: "The more production relies on the network, the more severe the potential damage in the event of a failure. What are the benefits of highly flexible single-piece flow production when the system is paralyzed? This is why system availability and control technology services are a higher priority for us. With Beckhoff's technology, single-piece flow production runs both quickly and well." Mark Straka also confirms this: "Quick response to inquiries is often very important to us. After all, downtime costs can be very high, not only when repairing or replacing production parts. Speed is equally crucial, and to achieve this high speed, Beckhoff has been committed to technological innovation for many years, while providing various project support. It can be said that there is currently no application need that PC control technology cannot meet. In addition, compared with traditional PLC technology, the compact modular system helps us save up to 50% of control cabinet space and about 20% of hardware costs. Moreover, new needs, such as subsequent temperature compensation, can be responded to quickly and flexibly through EtherCAT terminal modules or terminal boxes."
Automation technologies that can meet the needs of various applications
In the key production line, the PC control system handles all automation tasks: machine tool operation control, HMI for setup and automated operation, fault information display and data archiving, data processing via a gateway, and NC control of the three-axis milling gantry. Five three-axis stations controlled by TwinCAT NC I are used for the profile milling machine, and another three stations are used for the key cutting machine. Key transport is achieved by 15 transport stations, and key blank feeding uses 32 servo axes driven by AX5000 drivers with integrated safety functions.
Each machine tool is controlled by a C6930 cabinet-type industrial PC, and each machine tool is connected to a 15-inch control panel CP6902 suitable for cabinet mounting, enabling visual programming using a TwinCAT PLC HMI. Wilfried Wengenroth believes it even provides sufficient performance for future system expansion: "High computing power and high-speed control tasks allow us to solve very challenging tasks, such as high-precision drilling control, or tool breakage monitoring in broaching applications by acquiring motor current. The TwinCAT Database Server also allows us to gain more benefits from PC control technology. It can be used to handle huge amounts of data without shortening PLC cycle time." EtherCAT-based universal data acquisition—which can be centralized or distributed as required—offers further advantages through the use of EtherCAT terminal modules in the control cabinet or directly through EtherCAT valve islands and EP1008 or EP2028 EtherCAT terminal boxes during field processes.
During the manufacturing process, the direct distributed acquisition of I/O data in the field via EtherCAT terminal boxes, EP1008 , and EP2028 can significantly reduce the required control cabinet space.
Single-cable technology helps save significant expenses
Since 2014, Aumat machine tools have relied on Beckhoff's Single Cable Technology (OCT) in its drive products. This technology integrates the power and feedback systems into a single standard motor cable, significantly reducing hardware and debugging costs. Mark Straka stated, "OCT technology offers us a huge advantage when building systems, especially because it greatly reduces labor costs and error rates. Additionally, the amount of cable used is reduced by half, and the cable routing is more compact and scalable, which in itself saves nearly 30% in costs." Wilfried Wengenroth also saw two other advantages: "Because data transmission in OCT technology is very stable, electromagnetic compatibility is no longer an issue. Another advantage is the ease and speed of parameter setting in OCT technology. The significant savings in working time and raw materials greatly reduce the engineering requirements for programmers."
More information: www.beckhoff.com.cn
