Pilz Launches New Controllers to Promote Safe Motion Monitoring
What is safe motion monitoring and why is it important to protect your machine?
As machine safety becomes more complex with advancing technology, so do the safety controllers. Typically on a small machine, you might have a door and an emergency stop. These simple inputs would be connected to a safety relay that monitors signals and uses dual redundancy outputs to make sure the system is safe.
Once you start adding more than three safety devices, it’s time to look into using a safety PLC. Automation manufacturer, Pilz, recently launched both small and medium safety PLCs with expandable inputs and outputs.
The PONZmulti resides in the small PLC category but still has expandable I/O. The PONZmulti allows an engineer or technician to configure and program a complex safety system using graphical configurator software.
The PNOZmulti Configurator. Image used courtesy of Pilz GmbH & Co. KG
The configuration software uses simple flow chart-style graphical programming to monitor safety signals and condition safety outputs. The software contains standard safety components that can be dragged and dropped into the program and configure settings like switch type and which signals are wired to which inputs and reset functions.
Safe Servo Axis Monitoring
Pilz has added to the expansion modules for the PONZmulti 2 by adding a servo drive axis monitoring module that can monitor up to 8 different axes at one time. The advantage of monitoring an axis in the safety controller is to provide safe axis functions like (STOP FUNCTIONS);
- Safe Stop: A stop command is issued, and the axis comes to a controlled stop before STO is removed (safe torque off)
- Safe Operating Stop: The axis is commanded to a position before a stop command is issued then STO is removed
- Safe Speed Limiting: The speed or velocity of the axis is limited in certain scenarios. If the axis goes over the limited velocity a safe stop command can be issued
The PNOZmulti PLC. Image used courtesy of Pilz GmbH & Co. KG
An additional feature of the PONZ m EF 1MM2DO module is “cascading output.” This feature allows the user to configure delayed shutdown of other linked modules and controllers. The advantage is to allow other axes that are linked time to come to a stop and reduce damage to other tooling on the machine.
Typically, a safety controller doesn’t have access to the axis, so when an operator presses the emergency stop button, all axes connected to that safety system come to an uncontrolled stop. This kind of stop is hard on the axis breaks. Servo axes are becoming more common use in machine building because of accuracy, speed, and availability. Using a servo axis in an unconventional manner requires unconventional control of the axis safety.
Servo drives are just now hitting the market with safety functions, but they are expensive and require PLC programming skills. With the PONZ m EF 1MM2DO and the PONZmulti 2, a technician or engineer can implement the safety functions into virtually any servo axis on the market and integrate it into any machine control system. When designing a servo drive system with multiple or single axes, the PONZmulti 2 may help reduce time to market and provide a safer system.