Advantage through encoderless safety
What is the goal of functional safety? To keep the risks posed by technical equipment to humans and the environment as low as possible. Machining or machine tools can endanger operators or technicians, e.g. with tools that rotate at high speed. Drive technology that ensures the required safety functions without encoders offers the user various advantages.
To avoid dangerous operating conditions, safety functions limit the speeds, directions of rotation or axis positions. The objective of the drive controllers with integrated safety functions and the safety PLC in the KEB portfolio is to realize this particularly economically. Compared to previous solutions with classic, safe encoder feedback, the new development COMBIVERT S6/F6 PRO provides many functions even without an external encoder. This minimizes the wiring effort and simplifies the safety concept. In some applications with compact motors or high-frequency spindle motors, encoder mounting is not possible for safe monitoring functions. Since, for example, speed monitoring is usually dependent on encoder signals, new concepts for safety functions without sensors are necessary. In addition to more individual machine concepts, encoderless safety functions in the drive offer cost-efficient options for simple drive monitoring. Furthermore, maintenance and repair costs are reduced.
Encoderless safety functions can be used in various applications. One example is machine tools in the form of CNC machining centers, with which several machining steps can be carried out on one workpiece. They include functions of turning, milling and drilling machines and are suitable, for example, for complete machining of materials such as wood, plastic, glass or metal.
Safe functions are exemplary for precessing machines:
- SLS (Safe Limited Speed)
With the SLS function, the drive reliably monitors the speed. If the set speed limit is exceeded, an error reaction occurs, which was defined during project planning. The SLS function protects tools from overspeed.
- SLA (Safe Limited Acceleration)
For this purpose, the SLA function monitors the acceleration ramps. It prevents the motor from exceeding the defined limits during acceleration.
- SS1 (Safe Stop 1)
The shutdown of the drive is safely monitored by the SS1 function. The torque is then switched off (safety function STO is activated).
- SDLC (Safe Door-Lock Control)
The SDLC function can be used to lock the hood of the machine. This function only opens the hood when the motor has come to a safe standstill (e.g. for tool change).
- SSM (Safe Speed Monitor) and SMS (Safe Maximum Speed)
SSM provides a secure digital signal for speed monitoring with which other plant components can be controlled. SMS permanently monitors a maximum speed without having to activate monitoring.