Schunk has developed the EGK small parts gripper for handling delicate and fragile workpieces. It scores points for demanding and varied tasks in the laboratory industry or electronics production. The SoftGrip gripping mode ensures reliable parts handling. © Schunk

However, a force impulse occurs during the gripping process - in the millisecond range - which is detrimental to sensitive components and can lead to damage. This is particularly relevant in the electronics industry, for example, when handling sensitive electronic components from a pick-and-place machine, and sensitive scenarios are also conceivable in the laboratory. Schunk has differentiated the gripping modes to take these application-specific features into account.

Softgrip mode for gentle handling

The Softgrip gripping mode is suitable for handling sensitive, fragile or breakable workpieces, such as electronics, glass or ceramics. The overall lower gripping speed virtually eliminates force peaks. Customers can pre-position up to 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 constantly 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.

Handling heavy parts with Stronggrip

The EGU universal gripper is used for industrial handling of heavy, robust and insensitive components - for example in automated machine loading. A lot of gripping force is often required here. The gripping technology expert has developed the Stronggrip mode for these application scenarios, which gets more force out of the gripper than is apparent 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 all work together in the gripper. The Schunk designers have now inserted a flexible claw coupling between the upper spur gear and the output pinion. This element is used to maintain the gripping force and at the same time implement the Stronggrip function. For the gripping process, the motor is first briefly overcurrent and the workpiece is gripped; the relatively high energy input is used to build up a higher gripping force, which is greater than the nominal gripping force. After this gripping process, the brake is applied and freezes the elastic deformation in the claw element. The motor is now switched off so as not to overload it thermally; at the same time, the high gripping force is stored in the system with virtually no loss.

The new EGU and EGK products were launched at the end of 2022 and had already completed extensive endurance runs and long-term tests before being released for sale. In addition, Schunk was able to gain new insights from further, subsequent tests in practical continuous operation and explore the system limits even further. This means that software adaptations can be made to the existing hardware in terms of performance. With the software release, the achievable gripping forces in Stronggrip mode on the EGU can even be increased once again - from the previous maximum of 150 percent to 200 percent of the nominal force - except for the EGU 70 model.

The use of all potentials on the software side gives users full flexibility for different handling tasks - with one and the same gripper. "Stronggrip mode can be called up at any time," explains Benjamin Schell, Product Manager at Schunk. "The user can specify that the brake is applied and the motor current is stopped after gripping in basic grip mode. This has the advantage that the gripper is now in a kind of eco mode because the power consumption is significantly reduced," continues the product manager.

In addition to the new flexibility provided by the gripping modes, the standard communication interfaces - including Profinet, EtherNet/IP, EtherCAT and IO-Link - 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," continues Benjamin Schell. "In future, all mechatronic grippers from Schunk will be based on this new software platform - making customer systems future-proof, consistent, sustainable and powerful."

This article appeared in issue 10/23