Product category:
Vision and scanning systems
News Release from: Cognex UK | Subject: Checkpoint 900 vision system
Edited by the Manufacturingtalk Editorial
Team on 22 July 2003
Machine vision gets 'Best-In-Class'
bottle quality
50ml bottles presented some special challenges in eliminating all manufacturing irregularities until machine vision systems were used to automate the inspection process.
Machine vision achieves 'Best-In-Class' bottle quality As a leading supplier of plastic packaging to the pharmaceutical, cosmetic, food and beverage industries, Algroup Wheaton has long been known for its "best in class" pledge to quality with a relentless passion for performance improvements Among many of the packaging products produced at Wheaton are 50ml polyethylene terephthalate (PET) miniature plastic alcohol bottle, which are currently manufactured at three Wheaton facilities in North America
This article was originally published on Manufacturingtalk on 17 Sep 2001 at 8.00am (UK)
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When it was discovered that the 50ml bottles presented some special challenges in eliminating all manufacturing irregularities, the Wheaton plastic operations vision and automation team initiated an effort to maintain Wheaton's uncompromising standard of quality.
Realising that achieving defect levels measured in parts per million, can only be achieved through a combination of process control and 100% vision inspection, Wheaton initiated a pilot program for the automated inspection of bottles produced at the New Jersey facility.
The Wheaton team, having pioneered the use of vision technology with numerous implementations since 1980, was familiar with the added value of vision inspection.
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Cognex have introduced the In-Sight 2000, an entirely new type of industrial machine vision sensor at a cost usually associated with "smart cameras"
With this knowledge they looked to install a state of the art vision system that could inspect for a variety of imperfections not tolerated by high-speed lines and filling equipment.
For example, the 50ml's shoulder strength is extremely important and must withstand significant head pressure and torque in the capping and filling operation.
Any defect that could compromise the integrity of this area is an inspection attribute for the vision system.
Other challenges included skewed label placement, which could compromise the aesthetic quality of the bottles, and improperly formed bottle tops, which could cause leakage.
In addition to performing reliable and repeatable inspections, the vision system chosen would need to inspect at a high-speed rate of three bottles per second to accommodate Wheatons' high production requirements.
After evaluating several systems, Wheaton chose to install a Checkpoint 900 vision system from Cognex.
The system, which combines a PC plug-in vision processing card and a library of vision software tools for analysing images, works in conjunction with a Pentium 166MHz PC in an industrial cabinet six feet from the line.
After bottles have been blow-molded and labeled, they travel on a conveyor downstream to the inspection station, where three video cameras sequentially inspect the bottles.
The first camera, mounted above the conveyor, performs the bottle top inspection.
As a bottle comes into the camera's field of view, overhead lighting reflects off the bottle top and an image is acquired.
The image is then sent to the Checkpoint system, which analyses the image and determines whether or not the overhead illumination has formed a bright ring around the bottle top, suggesting that a good part is present.
A fail signal is elicited in the event that dark spots appear in the ring of light.
The second camera, positioned directly parallel to the neck region of the bottle, looks for minor indentations in the bottle shoulder over a 360 degree radius.
During this inspection, a pattern of lines is projected across the bottle's neck, and the vision system is used to detect any deformity in the lines.
The third camera looks directly at the label area to determine that the label has been applied in the right spot and without skew.
To do this, the vision system uses specialised edge detection software tools to measure and verify the X, Y, and theta position of each label.
If a bottle fails any of the inspections, the vision system sends a reject signal to a PLC.
The PLC then triggers a reject mechanism, which removes bottles from the line upon reaching the reject station.
Bottles that pass the inspection continue to move downstream, eventually falling into large plastic bags that are boxed up and sent to the customer for filling.
In addition to performing the inspections reliably at very high line speeds, the vision system has helped Wheaton improve their process control.
If the system detects three bottle imperfections in a row, an alarm is signaled, alerting operators that the production line has an irregularity and may need to be adjusted.
For example, a succession of skewed labels may suggest that tiny vacuum holes, which are used inside the blow-molding machine to hold labels in place before they are applied, are dirty and need to be cleaned out.
In this case, an operator could simply clean out the vacuum holes to restore vacuum strength, thereby fixing the problem and preventing additional labeling defects from occurring.
The vision system also records pass/fail data for each bottle as it inspects, including data about which types of defects are found, providing Wheaton quality assurance engineers with more information about their process.
Perhaps most importantly, the vision system has ensured that every bottle leaving the Mays Landing plant is entirely free of imperfections.
In doing so, the Cognex system has not only met Wheaton's expectations, but has enabled them to adhere to their best-in-class pledge to quality.
With the New Jersey effort a success, the company is currently looking ahead to the possibility of adding Cognex Checkpoint 900 vision systems to its other 50ml production lines throughout North America. Request a free brochure from Cognex UK ...
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