Total quality inspection of bottle products after filling process

Citation

(2005), "Total quality inspection of bottle products after filling process", Sensor Review, Vol. 25 No. 4. https://doi.org/10.1108/sr.2005.08725daf.002

Total quality inspection of bottle products after filling process

Total quality inspection of bottle products after filling process

Keywords: Machine vision, Image sensors

Original Juice Co. found itself with a challenge when it came to achieving consistent results in the placement of a bottle cap onto a product bottle after the filling stage. It wanted every bottle cap that gets twisted onto all of their different product bottles to be applied fully, to be applied straight and not skewed, and ensure that the tamper- band is not broken on those particular products that require one. The company looked to install a state-of-the-art vision system that could inspect a variety of imperfections not tolerated on high-speed lines and filling equipment. The shoulder strength of the various bottles is very important and must withstand significant head pressure and torque in capping and filling stages of operation. Any defect that could compromise the integrity of this area is an inspection attribute of the vision system. In addition to performing reliable and repetitive applications, the vision system chosen would need to inspect at a high-speed rate of up to 300 bottles per minute to accommodate the high production requirements of Original Juice Co.

To address this, Original Juice Co. began working with SciTech Pty Ltd, which has a long history of machine vision experience as a Cognex Integrator.

The process began with SciTech performing an on-site trial. The results met the satisfaction requirements of all involved and proved that this project was feasible and would be of enormous benefit in ensuring that every bottle leaving the Original Juice Co. plant is entirely free of imperfections. The trial focused on one bottle product only. On conclusion of the trial period, work began on implementing a full system that would cater to all current bottle products and also be scalable in order to accommodate any new bottle and cap types in the future.

SciTech chose to use the Cognex In-Sight^® range of industrial machine vision cameras (Plate 3). In-Sight 5100 and 5400 machine vision sensors are the highest performance models of the industry-leading family of In-Sight vision sensors. SciTech was confident in choosing the In-Sight 5100 to satisfy the inspection requirements involved. The In-Sight 5100 incorporates a die- cast aluminum housing and sealed industrial M12 connectors and achieves an IP67 rating for dust and wash-down protection on the factory floor. These environmental attributes would prove to be crucial in withstanding the wet, citric-acid environment of the inspection site as a result of the juices produced as well as the cleaning chemicals used in the area. This also required that the fixtures and fitting to be built using only stainless steel material.

Plate 3 Two Cognex In-Sights, two red LED backlights

The overall system consists of a touch-screen industrial PC incorporated into a stainless steel enclosure. The enclosure also houses the ethernet hub, the digital power supply of the lights, a PLC and various power distribution components. After bottles have been filled and capped they travel down the conveyor line, where two cameras sequentially inspect the bottles (Plate 4). The first camera looks directly at one side of the bottle and inspects the bottle cap at this side only. A red LED backlight provides the camera with a silhouette image of the bottle. Back lighting provides maximum contrast between the product outline and its background and is ideal for measuring external part edges. This results in images that work extremely well for the vision sensor's measurement and inspection tools. When the bottle comes within the camera's field of view, a sensor is triggered and an image is taken. The Cognex In-Sight software tools then analyse the image for defects and determine whether a bottle is defective or not. In the event of a failure being detected, a fail signal is sent via one of the camera's outputs to the PLC. The PLC then triggers a reject mechanism, which removes the bottle from the line. After passing the first camera, the bottle will travel a little further before the second camera acquires another image of it.

Plate 4 Camera inspecting 600ml wedge cap bottles

The second camera, mounted similarly to the first camera except at the opposite side of the conveyor, focuses on the other side of the bottle cap. The same inspection criteria apply equally to this camera. All defective parts are knocked off the conveyor line into a reject bin. A red beacon also becomes illuminated for 5 s when a bottle defect is noticed, notifying the operator. Good parts are simply allowed to continue unhindered on the production line. During this inspection a pattern of lines is projected onto the bottle cap and bottle, and the vision system is used to detect any deformity in cap height on the bottle, cap presence or absence, tamper-band presence and quality, and cap skew. To complete these tasks the vision system uses edge detection and histogram software to measure the cap, analyse the angle of the cap and determine cap presence.

Operator-friendly

Because of the number and variation of bottles involved, the system would need to be able to accommodate easy product changeover. The mechanical fixturing was designed with this specific requirement in mind. The cameras, backlights and sensors were mounted onto one fixed bracket that could be moved vertically via a turn wheel by the operator to accommodate the different height requirements of the bottles involved. The changeover procedure requires a height- determining tool to be temporarily attached to the fixture. Using a turn-wheel, the operator screws the tool down to a position whereby the tool rests gently on top of the bottle lip. When the tool rests on top of the bottle lip, the correct camera/light/sensor position for that product has been set. On completion, the operator removes the height- determining tool from its slot.

The final step in the changeover procedure is the operator makes a selection, via a custom application, using touch commands on the computer's screen. This screen uses a tab-style interface to segregate the different bottle types appropriately. Each tab has a descriptive name indicating the different bottle categories. On selecting the appropriate tab to the bottle type being run, a corresponding button appears that when pressed loads the correct vision file associated with the new product being run on the line. On successful completion of this step, the main software interface screen will contain the descriptive name of the bottle type selected. The changeover procedure is now complete and the line is ready to run.

When the line is running, a custom application on the VGA touch-screen monitor shows the last failed image acquired from each camera. The cameras also FTP their data back to the PC which is stored in text files. This provides Original Juice Co. quality engineers with more information about their process.

Plate 5 Bottles passing vision inspection station

The vision system's key asset is preventing defectively sealed bottles from being shipped to customers (Plate 5). Most importantly, the vision system has ensured that every bottle leaving the Original Juice Co. plant is free of imperfections. This has allowed Original Juice Co, to adhere to their pledge in high-quality products.

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