User report Stroke precisely monitored to one-hundredth of a millimeter
Pressing is a joining procedure that has traditionally been used in the manufacture of gear unit components and it is still the leading process today. Because the force applied allows a variety of different components to be durably joined, pressing applications are found in almost every sector of industry. This also applies to door drive system manufacturer GfA ELEKTROMATEN GmbH & Co. KG in Düsseldorf. The company uses presses to join worm gears and ball bearings to the hollow shafts of gear units for about 5,000 different types of drive system.
The joining process is started by scanning a barcode. An entirely new type of press then calls up the parameters required for the component concerned. As soon as the manually preassembled components have been positioned in the working area of the spindle, which is protected by a light curtain, the operator only needs to press a button to start the high-precision pressing process. The pressing of worm gears and bearings onto the shaft is a key step in assembly. GfA would have needed a considerable amount of retooling and retrofitting work to adapt its previous hydraulic presses to its new requirements.
Instead of transforming its previous hydraulic machines into networked press systems capable of data processing with additional measurement systems and special software, Hanen opted for a “dynamic solution with the DNA of modern tightening systems”. The Düsseldorf company started by trialing a PST unit from Atlas Copco Tools as an alternative to its hydraulic presses. The new unit promised greater accuracy, higher process security and fast, economical operation, with press spindle travel speeds of up to 500 mm/s. The Head of Assembly is also pleased to report that “the new tools are all-electric and no longer need any oil or filter changes. This reduces the environmental impact of production.”
The heart of the PST is a modified electric nutrunner spindle from the QST series which has been tried and tested in many thousands of assembly systems for safety-critical joints with mandatory documentation. The difference between the press and the nutrunner spindle is that the PST spindles convert rotation into linear motion which is then transferred in the axial direction via a planetary roller screw gear unit. The Swedish manufacturer has transferred the mode of operation of an electric nutrunner system with precise control and monitoring of torque and tightening angle to a linear system with control and monitoring of travel and force.
Sturdy and sensitive
Willi Hanen emphasizes that a PST can control the press force extremely precisely. He says that compliance with depth parameters is equally important for the optimum functioning of the gear units. This is where the user-friendly alternative to hydraulic presses comes into its own: “The pressing depth of the PST can be set precisely to one-hundredth of a millimeter and the measurement sensors of the electric spindle are extremely sensitive.” This provides valuable added benefits for production at GfA. For example, if an incorrect part were to be inserted in the press, the specified travel would not be reached even at maximum press force. “On the basis of our practical experience, the sensitive electronics detect such deviations absolutely reliably and stop the joining process.”
The component is only released following appropriate correction and inspection by the press system itself. Only then is the component, which has been unambiguously documented, inserted into the gear housing and transferred to the next processing step with the bearings and worm gears which have been joined to the hollow shaft in the optimum way. At the same time, the next component is scanned to initiate the next pressing process.
Smart connected assembly
During the pressing process itself, the PowerMACS 4000 controller of the PST acquires the joining data, documents them in a traceable way and transfers them to GfA’s Enterprise Resource Planning System (ERP) via Open Protocol. “We acquire all the quality-relevant information for further analysis and utilization via this closed data acquisition chain,” the Assembly Manager emphasizes. “There were no problems with establishing a link and we needed no additional hardware or software whatsoever for integrating the presses in our existing system,” Hanen reports. Furthermore, the system is fully compatible with Atlas Copco’s ToolsNet diagnosis program, which means that the data can also be used for additional detailed reports and diagnoses as well as for analyzing pressing results.
Better quality through traceability of all press data
“By combining the data with the serial numbers and photos of the components joined, we can demonstrate that our gear units have been assembled in accordance with the specifications across all assembly steps. However, Hanen believes that the evaluation of the assembly data gained via the PST system is just as important. “Thanks to these evaluations, we can further optimize our processes and exclude reworking. Our investment in the PST units has been rapidly recouped.”
“The PST presses are genuine Industry 4.0 solutions for our gear unit production. They perform high-precision joining operations, document all the quality-relevant information and actively avoid errors.”
- Willi Hanen, production manager with Gfa ELEKTROMATEN GmbH & Co. KG in Düsseldorf -
In Hanen’s opinion, the modular PST systems have further benefits for the assembly process: “These flexible units can cover our extremely wide range of gear units in its entirety. At the same time, the PST presses provide our assembly line workers with information on the process status at all times by optical signals and guide them through the entire joining process. Furthermore, the PSTs are extremely quiet, with 70 db(A), and up to 90 percent more energy-efficient than their hydraulic predecessors. This is another reason why we have now equipped all four gear unit assembly lines with these presses, which are designed for forces up to 100 kN (corresponding to about 10 metric tons).