It is a remarkable future platform that the technology leader from Lauffen is now presenting: different gripping modes for one and the same gripper for different handling tasks. Users can parameterize these gripping principles as desired according to specific needs. At the heart of the gripping modes is a new electronics and software platform that SCHUNK is constantly developing; based on field experience, existing gripping methods are improved and further possibilities are developed. In this way, customers using current generation grippers will also benefit from future adaptations and software updates. SCHUNK thus optimally exploits the potential of software in automation components in terms of flexibility, adaptability and ultimately sustainability, making its grippers fit for the future.
SCHUNK launched the two gripper series EGU and EGK in 2022. The electric universal gripper EGU is particularly suitable for flexible loading and unloading of machine tools, and scores as a reliable all-rounder for any handling task. The gripper for small components EGK, meanwhile, is designed for handling delicate workpieces that are susceptible to breakage, and is designed for demanding and varied tasks in the laboratory industry or electronics manufacturing. Together with these two series, SCHUNK has developed a software and electronics platform – both grippers share the same electronics and common software. Here, for example, a user, who uses both grippers benefits from consistent commissioning and programming of both gripper types. This saves time, as the operator no longer has to deal with the control of the new gripper. This cross-series and uniform functional concept provides customers with significant added value.
With the new software platform, SCHUNK has initially created three different gripping modes: BasicGrip, SoftGrip and StrongGrip. These different gripping methods open up a new dimension for users for differentiated handling of different parts adapted to the application. The previously common "normal mode" of BasicGrip is a gripping method with a time-optimized process sequence – this means that the gripping process is as fast as possible and achieves a high throughput. This mode is compatible with both the EGU and the EGK. The motor is permanently energized and the grip is permanently readjusted by the motor, which is particularly important for detecting workpiece loss. In BasicGrip mode, the workpiece is gripped with 50 to 100 percent of the nominal gripping force. The gripping speed is changed automatically by the gripper itself depending on the set gripping force.
However, a force pulse – albeit in the millisecond range – occurs here during the gripping process; this is disadvantageous for sensitive components and can lead to damage. This is particularly relevant in the electronics industry, for example, when handling sensitive electronic components from an assembly machine: During the brief force peak that occurs during gripping, too much gripping force acts on the component, which can cause PCBs to bend, fine hairline cracks to form or even individual conductor tracks to break. Similar sensitive scenarios are conceivable in the laboratory area: If too much gripping force is applied to a test tube or another sensitive medium with delicate contents during the force peak, cracks or even bursting can occur with unforeseeable consequences due to contamination. In order to take these application-specific features into account, SCHUNK has differentiated the gripping modes.
The SoftGrip gripping mode is suitable for handling delicate, fragile workpieces that are susceptible to breakage, such as electronics, glass or ceramic items. Due to the overall lower gripping speed, the force peaks are almost eliminated. Customers can pre-position to within a few tenths of a millimeter in front of the workpiece at maximum speed and then send the gripping command; pre-positioning compensates for a certain amount of cycle time and is relevant for all gripping principles. Even in SoftGrip mode, the grip is permanently readjusted by the motor. This method works in the nominal gripping force range of 50 to 100 percent and is available for the EGK small parts gripper, which is used in fragile handling scenarios.
The EGU universal gripper is used in the industrial handling of heavy, robust and insensitive components – for example in automated machine loading. A lot of gripping force is often needed here. The gripping technology expert has developed the StrongGrip mode for these application scenarios, which gets more power out of the gripper than would appear at first glance. This special feature is based on a special design trick: A brushless DC motor, a magnetic field brake, an encoder system on the central main shaft for position detection and a spur gear interact in the gripper. The SCHUNK designers have now inserted a flexible claw coupling between the upper spur gear and the output pinion. The gripping force maintenance and at the same time the StrongGrip function are realized with this element. For the gripping process, the motor is first briefly exposed to excess current and the workpiece is gripped; a higher gripping force is built up from the relatively high energy input, which is above the nominal gripping force. After this gripping process, the brake engages and freezes the elastic deformation in the claw element. Now the motor is switched off so as not to overload it thermally, and at the same time the high gripping force is stored in the system with virtually no loss.
Thanks to the elastomer module, it is possible to get more force out of the gripping system than would actually be possible according to the rated power. Due to the motor switch-off, no external energy is required after gripping, yet a high gripping force is effective and enables the handling of heavy workpieces. The application of the motor brake can be timed, but must occur after two seconds at the latest in order not to thermally overload the motor. In StrongGrip mode, the maximum gripping force can be called up. The gripping speed remains constant during the process. While it is true that continuous operation in StrongGrip mode can lead to higher wear of the mechanical components, it should also be noted that a pause between two gripping cycles is necessary in this force mode; for example, a pause of ten seconds is recommended for a gripping cycle with maximum gripping force and a post-gripping time of two seconds at an ambient temperature of 25 degrees Celsius.
The new EGU and EGK grippers were launched at the end of 2022 and had already undergone extensive endurance runs and long-term tests before being released for sale. In addition, SCHUNK has gained new insights from further, subsequent investigations in practical continuous operation, and has been able to explore the system limits even further. Thus, with software adjustments, the existing hardware can "catch up" in terms of performance. Thanks to the software release, the achievable gripping forces in StrongGrip mode on the EGU can even be increased once again – from a maximum of 150 percent to 200 percent of the nominal force – except on the EGU 70 model. With a doubling of the gripping force, users benefit from a real performance boost.
The software-based use of all potentials brings users full flexibility for different handling tasks – with one and the same grippe. "The StrongGrip mode can be called up at any time," explains Benjamin Schell, Product Manager at SCHUNK. "The user can specify that after gripping in BasicGrip mode, the brake is applied and the motor current is stopped. This has the advantage that the gripper is now in a kind of eco-mode because power consumption is significantly reduced," continues the product manager. This special feature – high gripping force with an unpowered motor – is a unique function and supports plant operators in implementing energy-saving processes.
In addition to the new flexibility gained through the gripping modes, the common communication interfaces – including PROFINET, EtherNet/IP, EtherCAT and IO-Link, for example – and a consistent control protocol for data exchange are plus points for the user. "No matter which interface is used, the operation is always the same," Benjamin Schell further explains. "Even when implementing a different gripper, users will always finds their way around. In the future, all mechatronic grippers from SCHUNK will be based on this new software platform – making customer systems future-proof, consistent, sustainable and powerful." SCHUNK assures that customer requirements and market feedback will flow into the further development of the software platform.
