Safety chaining of machines made easy

"Everything from a single source" - a promise you often hear. But with wireless safety, an aluminum safety fence, emergency stop buttons and a safety door locking device, not only was everything supplied from a single source, but in this case also offers a coherent safety concept for the automation of an injection molding cell. The injection molding cell consists of an injection molding machine, two robots and two conveyor belts for feeding and discharging.

Robot behind aluminum safety fence with Safety Simplifier safety controller and tGard as solenoid interlock

Safety linkage of the plants as a challenge

From a safety perspective, the greatest challenge was the safety interconnection of the machines and robots from various manufacturers. "We searched for a long time for a suitable safety system for our application, but no manufacturer was able to deliver a satisfactory solution. The linking of all machines was much easier with the wireless safety controller "Safety Simplifier" from SSP than with conventional systems."

Decentralized Safety PLC with Wireless Safety

Because the Plug & Play solution brings safety to where it is needed. SSP offers the decentralized safety PLC with Wireless Safety with 14 safe, digital inputs and outputs and optionally with two additional, double relay outputs. The user can then configure the 14 I/Os as desired and flexibly as inputs or outputs. For this solution, modules with 14 I/Os were selected for each door unit, and the modules on the control cabinets also have two additional relay outputs for potential-free disconnection of the robot and machine. The door modules are also directly equipped with the necessary operating elements such as emergency stop and illuminated pushbuttons. These can also be freely selected via an online configurator. The integrated LED display provides a quick overview of the inputs and outputs and provides further information about signal strength or number of participants.

Aluminum safety fence

Injection molding machine with Safety Simplifier and an external emergency stop EDI C7

Emergency stop system

If a system is interlinked, the emergency stop buttons must also be interlinked due to normative requirements, since in an emergency all machines or robots must stop by actuating a single emergency stop. The relay outputs of all Safety Simplifiers used switch together or individually, depending on the application, in order to be able to stop the machines safely. The power supply (10-30 VDC) can also be easily disconnected from the power supply of the plant. In this way, individual machines can also be switched off in a linked system without having to cause an emergency stop of all machines. Among other things, this simplifies the installation of emergency stop solutions, since no additional evaluation unit is required for the control system. Via the free software "Simplifier Manager" the modules were programmed with the support of SSP.

Wireless communication

Above all, this new concept also drastically reduced the wiring effort of the system, because the tGard safety interlock from SSP and external emergency stop buttons are simply connected directly to the Safety Simplifier with preconfigured connectors. This eliminates the need for additional safety control or wiring in the control cabinet. The Safety Simplifier now sends the signals wirelessly on a frequency of 2.4 GHz to the other participants in the system. The special feature here is that it is not a simple transmitter and receiver model, but through mutual multi-master communication, a comprehensive network of safety communication is established, in which each Safety Simplifier also serves as a repeater. Thus, even longer distances can be bridged reliably and quickly without the use of cables! If Denk Kunststoff Technik decides to use Safety Simplifiers on additional systems, there are still 15 channels available on the 2.4 GHz frequency so that they do not interfere with each other. In total, up to 16 Safety Simplifiers (256 I/Os) can communicate with each other in one system.

The Safety Simplifiers on the robot control cabinet safely shut down the robots.

Safe control

In addition, the user can benefit from a decentralized security concept at the same time. Simple functions can be easily added to existing as well as new systems. Functions such as "door closing" or "time-delayed opening" can be selected and directly connected to the safety outputs of existing safety systems and machine controls. A control cabinet for the safety technology and a higher-level safety switching device are no longer necessary in this case.

Safety door tumbler tGard

It is self-explanatory that the highest safety requirements are necessary for such an application, which is why SSP solenoid interlocks are used on the access doors. The solenoid interlocks from the Fortress Interlocks - tGard series can be individually adapted to the customer's requirements. tGard thus combines safety and operation. tGard is quick and easy to install because the modules can be mounted directly on flat surfaces, doors or on aluminum profiles without additional mounting plates or brackets. The compact and extremely robust metal housing provides the necessary stability and durability.

The tGard safety gate guard locking device on the safety fence is also connected directly to the Safety Simplifier.