23 Jul 2024


Safety-certified encoder will protect machine operators

The German sensor-maker Sick has launched a PLd / SIL2-certified incremental encoder that can be used to ensure safety in machinery requiring frequent operator involvement. The DFS60S Pro encoder allows operators to interact safely at slow speeds – for example, to load piece-parts or adjust machining centres – without needing to stop the machine.

The IP65-protected encoder fits directly to the machine’s rotating shaft, monitoring its speed and sending the data to a safe motion monitor. It can provide PLd / SIL2 safety using one encoder, or PLe / SIL3 if two encoders are used. The encoder is designed to be used with Sick’s Flexi Soft FX3-MOC drive monitor. It can be applied to new machinery or retrofitted to equipment where Flexi Soft systems have already been installed to operate other safety sensors and switches.

Although the encoder communicates shaft rotation continuously, it comes into its own after a slow speed phase is signalled – for example, if personnel are detected entering a safe zone. The drive monitor determines the shaft speed from the encoder data, and monitors pre-configured motion characteristics until it receives a clearance signal.

“The DFS60S Pro delivers easily-verified safety for controlled slow operations where production efficiency is key,” explains Sick UK’s encoder specialist, Darren Pratt. “Using non-certified encoders requires substantial investment in validation and verification of the safety function to ensure compliance with the Machinery Directive.

“For many machine types, safely-controlled motion is essential for personnel safety,” he adds, “but it is also increasingly important for machine-builders seeking to improve the productivity of machinery they build. Shutting off the whole machine when someone needs to interact with the machine or gets a little too near, can be very wasteful of energy and production time, especially if the machinery has to be totally re-initialised.”

The encoder’s drive shaft connection uses specially-engineered components, including a keyed drive which is recommended for shafts of all sizes, but is essential for shaft diameters below 10mm.