Vision system
for the inspection of plastic bottle stoppers

Disadvantages of corks in the production of bottled products

Our key task was to inspect the corks for cracks and eliminate them from the production line. Also inspected were irregularities in cork closure and tightening, colour inconsistencies, and missing corks on the production line.

What have we come up with? A vision system for the inspection of bottle stoppers

In the case of our client, the control of the production line was partly automated. In the first stage, a pneumatic reject system eliminated only those bottles that were incorrectly filled. The verification of cork defects took place at a further stage of the line and consisted of an employee visually assessing each produced bottle and manually removing it from the production process. Such distributed quality control was not efficient because the employee observed the bottles from a distance, which made it impossible to spot minor defects, had to manually remove non-conforming pieces (NOK) that were detected, and due to the high throughput of the production line was not able to work efficiently on a continuous basis. The state-of-the-art vision system we proposed ensured that every bottle produced was checked and human error was eliminated without slowing down the production process.

What was subject to a vision inspection?

The machine vision covered different types and capacities of bottles (7 formats), as well as several types of plastic stoppers in different colours (5 references). Bottles classified as defective by our vision system were removed using a pneumatic ejector.

How did we do it? Description of the vision system in detail

• In order to eliminate cracked corks from production, we used a camera to image the course of the laser beam projected onto the cork. A defect, such as a vertical gap at the base of the cork, was visible in the images as a break in the continuity of the laser line. We used a four-camera system to fully image the cork (360 degrees). The imaging took into account the speed of the conveyor belt, the distance of the bottles relative to each other on the production line, as well as sudden stops and shifts of the bottles.
• The colour of the cork was verified thanks to a dedicated colour sensor, which compared what it ‘sees’ at the top of each cork with a reference colour entered into the system.
• To check the level of liquid in the bottle, we used a camera with a telecentric lens to eliminate curvature of the bottle. By positioning the camera at a 90-degree angle to the bottle’s axis of movement, we were able to verify the fluid level, assuming vibration on the production line. From the photograph verifying the level of liquid in the bottle, we also checked the presence of the stopper, its tightness (in relation to the bottle collar) and the closure of the top flap.
• The processing and analysis of the images taken was done using a computer with sufficient computing power, which ran continuously without buffering. If a defective bottle was detected, the controller sent a signal to reject such a bottle from the production process.

What does the hardware architecture look like?

The vision inspection software was embedded on an industrial computer in a stainless steel control cabinet. An operator panel was placed next to the inspection station, which allows changes to be made, e.g. from a higher to a lower bottle, as well as the selection of the correct stopper for the product being inspected. The panel also provides production statistics such as the total number of bottles inspected, the number of defective bottles by type of defect and the percentage of rejects. The system allows data to be archived along with photos and type of defects. Multi-level access for technologists, operators and service is also possible to the operator panel. The possibilities of installing vision inspection were determined after an on-site visit to the customer’s production facility.

Visible change, real benefit

Our vision measurement systems were able to detect any cracks in the cork over its entire surface (360 degrees) with an accuracy of 99.9%. We measured the level of liquid in the bottle with an accuracy of +/- 12.5 mm, the correct application of the cork (adhesion) with an accuracy of 2 mm, and the tightening of the top flap of the cork with an accuracy of 0.4 mm. Our system was able to control production around the clock, with a production line capacity of approximately 25,200 bottles per hour. We adapted to the degree of automation of the production facility and thus managed to use the pneumatic rejector we already had. All of this enabled full collaboration and synchronisation of tasks: the vision system detects a defect – the rejector reacts immediately, and everything happens in real time, without delays or production downtime – zero compromise between productivity and quality. This comprehensive quality control fully eliminates the impact of worker fatigue, enabling more efficient use of staff resources. In addition, thanks to a system that records detailed information about every rejected product, the company’s quality department can analyse trends and improve the entire production process. All of this makes investing in modern vision systems a step forward, allowing you to stay ahead of the competition and strengthen your brand’s position in the market.