E-Grippers Deliver Benefits For Automated Assembly Applications

Recognised as experts in automation and handling technology, Zimmer Group now offer a series of highly functional and easy to control electrically driven grippers. Designed primarily for assembly tasks and for handling small parts, these latest generation products deliver a number of distinct advantages for automated assembly operations.

Electrically operated grippers from Zimmer’s GEP2000 series offer a number of advantages for small parts handling including: adjustable gripping forces of between 80 N and 400 N and jaw strokes of between 10mm and 16mm. Another important feature of this range of grippers is their mechanical self-locking mechanism, which prevents the loss of the workpiece in the event of a power failure.

All grippers within the range feature an integrated control system and are available in three control versions: With IO-Link, digital I/O and digital I/O plus an analogue output to set or interrogate the jaw positions. With the IO-Link version, the gripper offers all the system-specific advantages of that interface, which includes not only simple handling and operation, but also easy integration. By connecting a single cable, the gripper can receive data from and transmit data to the master controller. Parameters such as gripping force and gripping speed are set centrally. The gripper uses IODD (IO Device Description) to send signals to the higher-level control system.

The resultant benefits include considerable time savings during initial setup or when replacing the gripper. IO-Link also sets new horizons for advanced diagnostic functions and predictive maintenance, which in turn enhance machine availability. No additional hardware, in the form of other controllers is required thanks to this highly sophisticated control system. The IO-Link master is all that is needed to act as a link between the gripper and the fieldbus, and no additional software needs to be installed on any PLC being used.

Zimmer Group also provides its own Human Machine Interface (HMI) for easy operation. This tool, which has a special gripper- adjustment user interface, is able to store parameters for up to 32 different workpieces.

In the I/O version, the grippers operate as simply as a conventional pneumatic valve. The gripper opens when it receives a control signal, and the jaws are closed when it receives another one. In this cost-effective version, a four-pole cable that supplies the gripper with both electrical energy and control data is all that is required. A commercially available central distributor can be used to control several grippers at the same time. Should gripper position information be required, this can be achieved using magnetic field sensors, which can be accommodated in the two grooves incorporated within the gripper.

The gripper is able to use these sensors to send a signal as soon as a set query position is reached in just the same way as a traditional pneumatic gripper.

Zimmer Group has developed a simple solution for adjusting the maximum gripping force, which can be set directly on the gripper using a potentiometer with four separate positions. This is not only quick and easy, but also offers the advantage of the setting being easily visible, even if the power has failed or if the gripper has been removed.

For applications where more precise information relating to the position of the gripper jaws is required, Zimmer Group offers a digital I/O version together with analogue sensing. An analogue sensor, which outputs a voltage of between 0 and 10 volts, depending on the jaw position, is integrated into the gripper as standard. This voltage can be evaluated using an analogue card in a higher-level control system, making it possible to determine the position of the gripper jaws with an accuracy of less than 0.05 mm.

Robust Mechanical Design Delivers Longevity In Service

Zimmer Group’s GEP2000 series electrically powered grippers feature an industry leading mechanical configuration. The hard anodised aluminium housing is at the heart of the grippers’ robust construction and reliability, and the field proven flat guide design will allow the gripper to perform 10 million part handling or assembly cycles without requiring maintenance.

All versions in the range offer a mechanical emergency release, which is an important safety feature. Should there be a need for the gripper to be opened manually, in exceptional circumstances, the screw on the self-locking gearbox can be turned using a separate screw which is easily accessible externally. As a result, the gripper can still be opened, even in the event of a power failure when for example, a workpiece needs to be removed.

All grippers are sealed to IP40 standard, and their high accuracy allows for rapid replacement minimising any interruption of production. The grippers in the GEP2000 series are powered by 24 VDC, and the gripper jaws are able to operate with a current draw of less than 500 mA. The current draw only increases to 2 A, a current that all conventional IO-Link masters can supply, for a few milliseconds at the moment of start-up, when the mechanical self-locking mechanism is released, and the motor is being brought up to speed.