Safety in all its variations

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2015-07-25 15:18:45

One year ago, SCHUNK presented the world’s first certified safety gripping system. Now the competence leader for clamping technology and gripping systems is taking the next step by providing safety concepts for each of its three mechatronic pillars. The goal: an efficient method for uninterrupted collaboration between human beings and handling systems.

Mr Ralf Steinmann, director business unit for gripping systems at SCHUNK, is convinced that human-robot cooperation will extend throughout the entire production process in the medium and long term. "Instead of working next to each other in mechanically separated spaces as at present, man and robot will cooperate in a barrier-free environment in the future. Especially in assembly, there will be a drastic increase in the number of collaborating systems," Steinmann explains. While present-day systems generally have to be switched to a safe position in order to remove defective parts, to supply new parts or for troubleshooting, in the future the respective system components will only have to be temporarily slowed down or stopped for the duration of the human intervention. As soon as the safety zone is free, the system will automatically return to regular operating mode.

SLS, SOS, and STO

With the EGN and EZN safety gripping systems certified in accordance with DIN EN ISO 13849 SCHUNK already established a benchmark in 2014. In combination with the SCHUNK ECM controller and the SCHUNK ECS safety module, the ready-to-use modules enable SLS, SOS, and STO functions.

They fulfill performance level d and SIL 3. When used together with pressure mats, door switches, light curtains or 3D cameras for room monitoring it is possible to define different safety zones, without having to completely interrupt the production process by means of emergency shut-downs in case the contact between man and machine is too close. Instead, the grippers either switch to a safe limited speed or a safe operating stop, depending on the activated safety zone.

As opposed to existing solutions on the market the two safety gripping systems are supplied with power continuously in case of a safe operating stop, so that gripped parts are held reliably even without mechanical gripping force maintenance. As soon as the safety zone is released, the grippers switch directly back to regular operating mode without delay and without having to restart the system. This will allow new scenarios of direct man-machine cooperation. The gripping force, speed, and finger position of the modules can be adjusted and controlled flexibly during the handling process. A resolver which is connected directly to the motor, continuously monitors the position of the servo motor and enables exact positioning of the gripper fingers.

The EGN/EZN is controlled by the SCHUNK ECM controller, which features standard connection technology, either via Profibus (up to 12 Mbit/s) or CAN-Bus (up to 1 Mbit/s). This facilitates commissioning and parameterization via a PC, USB drive or rotary code switch. In order to use the certified SLS, SOS, and STO functions, the gripper and the controller are supplemented by the SCHUNK ECS safety module, which in turn monitors the resolver. No modifications to the gripper are necessary for this purpose. Due to the modular design the safety functions can be retrofitted at any time. Depending on the size, gripping forces of up to 1,000 N are possible.

Safety gripper for small components

With the SCHUNK EGP Safety, the world’s first performance-level d/SIL3-certified electric small component gripper on the market with omnidirectional gripping force safety, the innovative family-owned company now offers a ground-breaking solution for the handling of small components. Especially in complex assembly systems, the goal for the future is to minimize the necessity of complete system shut-downs. Instead, single stations switch to safe operating stop (SOS) in case of manual intervention. Reliable gripping of the parts is maintained, whether from the inside or outside. Ideally, other redundant stations will be activated in the meantime to perform the necessary tasks. As soon as the safety zone is released, the gripper switches back to regular operating mode without delay and without having to restart the system. The SCHUNK EGP Safety is controlled by a PNOZmulti safety controller from PILZ.

Monitoring is achieved by four inductive proximity switches. With this patent pending solution SCHUNK once again sets standards, because the combination of redundant monitoring with the safety module effectively fulfills the conditions for reliable gripping and safe stop functions. The EGP Safety therefore completely fits into the pillar of "alternative" mechatronic modules from SCHUNK, which can easily be used as a 1:1 pneumatic replacement. The safety version of the SCHUNK EGP likewise requires no internal or external controller. The safety controller is simply placed in the control cabinet and connected to the sensor distributor.

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