PDC Sensor for Label Detection - Ultrasonic Through-Beam Fork Sensors for Transparent Label Detection in Packaging Automation
This technical article explores the ultrasonic through-beam fork sensor technology for label detection in packaging automation, covering the operating principle of ultrasonic attenuation measurement, the calibration and teach-in procedures, the application for transparent and metallized labels, and the integration with labeling machines for precise label placement.
The ultrasonic through-beam fork sensor for label detection operates by measuring the attenuation of an ultrasonic signal as it passes through the label and backing material. The fork sensor has an emitter and receiver arranged as a light barrier in a single housing, detecting even the smallest change in ultrasound attenuation. The attenuation results from the different material thicknesses of the base material with label and the bare base material. An ultrasonic transmitter in the lower leg of the fork beams a fast sequence of pulses through the backing material. The sound pulses cause the backing material to vibrate, generating a greatly attenuated sound wave on the opposite side, which is received by the receiver in the upper leg. The sensor evaluates the signal difference between the backing material and the label to detect the label position. The fork sensor's compact dimensions enable installation in space-constrained labeling machines, while the robust metal housing ensures reliable operation in demanding industrial environments.
PDC Sensor
The calibration and teach-in procedures for label detection sensors are designed for quick and reliable setup. The QuickTeach method simplifies the teach-in process, where the sensor learns the material for the duration that the button is pushed or pin 5 is controlled. The sensor provides three different teach-in methods for different applications: dynamic learning of both backing material and labels, separate teach-in for backing material and labels, and web-only learning for splice detection. The teach-in procedure can be carried out with the button on the top of the housing or with pin 5 on the unit's connector. With LinkControl, the sensor can be parameterized and measured values can be shown graphically. The calibration ensures that the sensor's switching thresholds are optimally set for the specific label and backing material combination, providing reliable detection even for challenging materials.
The application for transparent and metallized labels is where ultrasonic fork sensors excel. Optical sensors struggle with highly transparent labels, as the light beam passes through without sufficient attenuation. Ultrasonic sensors, however, use sound waves that are attenuated by the material regardless of its optical properties. The esf-1 can reliably detect high-transparency, reflective materials as well as metallised labels and labels of any colour. The sensor's ability to detect labels on any label material regardless of color, transparency, or surface finish makes it ideal for applications with diverse label types. The sensor also detects labels with weights from less than 20 g/m² up to over 400 g/m², metal-laminated sheets and films up to 0.2 mm thick, and self-adhesive films, providing versatility for different labeling applications.
The integration with labeling machines for precise label placement requires accurate detection of label position and gap. The sensor's response time of less than 300 µs ensures that the label position is detected with sufficient precision for high-speed labeling. The sensor provides two switching outputs for label/splice detection and web break monitoring, enabling comprehensive control of the labeling process. The IO-Link interface supports remote configuration and diagnostics, and the Smart Sensor Profile enables more transparency between IO-Link devices. The sensor's ability to detect labels with 1 mm gap accuracy enables precise label placement, reducing waste and improving product quality. The sensor's compact design and robust construction ensure reliable operation in the high-speed, high-vibration environment of labeling machines.
The future of ultrasonic label detection is focused on enhanced connectivity and intelligent diagnostics. The integration of IO-Link communication enables remote monitoring of sensor status, signal quality, and diagnostic data, supporting predictive maintenance and reducing downtime. The development of sensors with multiple teach-in memories enables rapid changeover between different label types, reducing setup time. The ongoing advancement in transducer materials and signal processing is improving the resolution and sensitivity of ultrasonic label sensors, enabling detection of even smaller signal differences. The ultrasonic label sensor remains an essential component in modern packaging automation, providing reliable, non-contact label detection for efficient, high-quality labeling operations.
