Automated inspection of glass bottles using a profile scanner
The scanCONTROL laser profile scanner from Micro-Epsilon can be used in factory automation applications such as presence monitoring systems. Typical uses have previously been the detection of the empty containers at bottlers and breweries. A system based on the laser triangulation principle is installed for carrying out this presence monitoring operation, which is used when the bottle crates are received.
In a brewery or bottler, the main challenge with performing measurements on glass bottles is the reflective properties of the bottles. These properties vary due to different glass colours — such as green and brown — and also because bottles come with or without a lid. Performing measurements on bottles can also be very difficult due to the constant vibration and shaking of the bottles while they are being transported on the conveyor belt. The scanCONTROL 2900-50 offers a real-time surface compensation feature in which the exposure time and the threshold of reflection detection are adapted in real time in order to generate stable measurement results.
The scanCONTROL 2900-50 laser scanner features a special line-scanning optical system that ensures a uniform exposure of the measuring field. It operates according to the principle of optical triangulation. A laser light is projected onto the target surface via a linear optical system — the diffuse reflected light from the laser line is then replicated on a sensor array by a high-quality optical system, which then evaluates the image in two dimensions. It offers precision measurement even in harsh environments.
Crates with empty bottles are sent for inspection to determine whether the correct type of bottle is in the crate, if the height of the bottles is appropriate and if any bottle is missing from the crate. To perform this automated inspection, the inline monitoring system is equipped with five scanCONTROL 2900-50 laser line triangulation sensors, and the crates on the conveyor belt are scanned from above. The laser scanners are located in such a way that each scanner measures a row of bottles in the crates. The monitoring is carried out at speeds of up to 850 mm/s. The scanners measure the height of the bottles in the crate based to detect any that are not fitted correctly. While doing so, they ensure that the height of the bottles does not deviate more than 3 mm from the target height for the respective bottle type.
In addition to the high-speed measurement, the system also provides access to logged data for subsequent statistics, evaluation and process optimisation. The measured values are evaluated directly inline via a GigE Vision interface that integrates the raw data into the image processing software and then further evaluates it. The final result of the presence monitoring is received by PLC as an ‘OK’ or ‘not OK’ value, whereby any faulty crates can be removed directly. The results can also be displayed via an integrated display on the control unit.
Other factory automation applications
Automated inspection has become particularly important in production lines in the manufacturing of steel, plastic, fabric, paper, coated board, chip packaging and the food and beverages industries. The typical applications of laser profile scanners in factory automation are in measuring diameter, thickness profiles, and edge defects of pizzas, measuring the size and weight of biscuits, inspecting labels on cans, assessment of fruits, vegetables, cheese, noodles and meat. The scanCONTROL laser scanners are available in different laser types and with a comprehensive range of accessories so that numerous measurement tasks can be solved for different industries.
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