Automation expert SCHUNK has expanded its mechatronic gripper portfolio with the EZU three-finger gripper. There was a good and highly topical reason behind this: it was urgently needed! "We had a challenging handling task to solve," reports Peter Liebal, design team leader at WEKAL Maschinenbau in Fritzlar. "And this was where SCHUNK came in, supplying us with a custom-fit electric gripper." The mechanical engineering company had several robot cells for different loading, transfer and feeding processes in the works. The customer, a well-known automotive company, is successively integrating these cells into its existing production line with a view to improving defined processes through automation. "We have been working with the automotive company for a long time and have already supplied several line modules," explains Peter Liebal. "Our reliability and quality are well-known there."
WEKAL specializes in manufacturing customer-specific feeding and robot solutions, however, the designers encountered a problem with a tricky handling task in a linking cell. In this cell, axle drive wheels are fed to the robot as raw parts via blister stacks. It automatically picks up the blanks from the blister layers and feeds them to the linking system; subsequent processing stations in the line might be, for example, a washing system, a deburring station or a milling machine for the serration. "The handling challenge in this cell incorporates several aspects," explains the design manager. "The axle drive wheel for an electric motor, which weighs around six kilograms, has a very smooth surface. That's why we need a high gripping force here. The next aspect is the 'misalignment' of the components," says Liebal, describing the challenge: "The axle drive wheels are not always exactly centered in the blister grid and can be somewhat misaligned. "For example, the components can slip in the blister mold due to transport between different process stations and vibrations in the environment," explains Peter Liebal. "In addition to this slightly eccentric position, the stacked blisters bend under their own weight and the components tilt slightly in the blister grid." The gripper masters this special position by compensating for horizontal displacement, and can still handle the axle wheel safely and reliably. "The EZU manages to compensate for both the horizontal displacement of the component and the slight tilting when gripping. This is a special feature of this gripper," highlights Liebal.
In their attempt to solve this particular problem, the WEKAL design team had also tested a competitor's product - but with this product, although several individual solutions were tried, the gripper lost the component during the process. "This has once again proven that SCHUNK is the right partner for us when it comes to gripping technology," says Liebal. His team was already familiar with the EGU electric two-finger gripper, which is installed elsewhere in the line. "We liked it a lot," confirms Liebal. The design engineers at SCHUNK thus registered the need for a corresponding three-finger module for this special handling solution. "And SCHUNK delivered," says Peter Liebal. "SCHUNK did everything it could to provide us with an electric three-finger gripper in the shortest possible time, exactly as we needed it - compact in design and with a high power density, which was exactly what we required for this process."
It is not a matter of course that a supplier will respond so promptly to a customer requirement, the team leader points out. "The newly developed EZU from SCHUNK was a perfect fit for our requirements, and I can well imagine that other users will also like the features of this gripper." Christian Glatzer, who is responsible for robotics and programming at WEKAL, is also convinced of this: "The synergy between the EGU and the EZU is very valuable to us," affirms Glatzer: "We have the same interface, the same software platform, which makes everything very simple. We can put it into operation without any problems and can switch flexibly via plug and play. This user-friendliness saves a lot of time."
An integrated absolute position measuring system detects the diameter of the workpiece and ensures permanent referencing even in the event of an emergency stop or power failure. "Another advantage is the PROFINET communication interface integrated into the gripper. It does not require an additional gateway; the connection is seamlessly integrated into the control system network. This is also very convenient for our customer, who will ultimately operate the system," explains Glatzer. The high gripping force of the EZU is also impressive. "SCHUNK has done a fine job with the re-gripping function," emphasizes Glatzer. The spur gear ensures that the gripping force is generated particularly reliably without a minimum approach distance. The permanent re-gripping ensures maximum process reliability and compensates for the positioning inaccuracies that occur in everyday production. In addition to the normal BasicGrip mode, users can get even more power out of the gripping process - in StrongGrip mode, the gripping force can be increased by up to 200 percent. This would enable WEKAL to handle even heavier workpieces without having to change the gripper. Like the EGU, the EZU is also equipped with integrated gripping force maintenance with workpiece loss detection.
With the expansion of its mechatronic gripper portfolio, SCHUNK is supporting the process of electrification that can be observed everywhere you look. This also falls in line with WEKAL customer's objectives. "Even if we supply the car manufacturer with a turnkey handling cell for integration into the production line, they still have to keep an eye on which components are installed. Electrical modules also had to be installed, especially in the production of electric motors," Peter Liebal points out. "The customer was delighted with this solution with the EZU." Four automation cells have already been delivered. Four more cells are to follow - including a cell in which EGU and EZU work together efficiently during the handling process, thanks to synergies.
SCHUNK has provided three sizes of the EZU centric gripper, thus enabling WEKAL to grip all rotationally symmetrical components in the application. "We have installed various pieces of gripping technology from SCHUNK in many gantry solutions and robot cells, as SCHUNK has been an established supplier of professional gripping technology for many years," confirms Peter Liebal. "But we were particularly impressed by this solution. Thanks to the individual approach to resolving this particular issue and the close collaboration, we were able to reach the optimum goal through joint discussion."