Shapely glass bottles pass inspectionShapely glass bottles pass inspection
March 11, 2015
It's only logical that packaged goods like fragrances and cosmetics, designed to make users look and feel more attractive, have to be especially attractive themselves. The emphasis on appearance can be a tall order for the glass bottle manufacturer, called upon not only to produce attention-getting shapes that reflect the individuality of the contents but also to make sure each container shipped is absolutely flawless.
So when glass manufacturer Saint-Gobain noticed occasional dark smudges on the surface of glass vials emerging from a production line in La Granja, Spain, plant director Antonio Jiménez-Heras knew it was time to take action. The COSMOS,™ a multi-camera cosmetic defect-inspection system developed specifically for the glass container market by AGR International, Inc., was the right solution for inconspicuous bottle defects. The inspection system combines machine vision and defect identification know-how with new (patent pending) proprietary, light-filtering technology to craft a system that spots both visible and hard-to-see surface defects in glass containers?flaws that traditional vision systems typically overlook.
"Customers today are much more demanding than they were even ten years ago," Jiménez observes. Not only is there zero tolerance for critical defects that could cause breakage, but the aspect quality level has to be much higher. This is especially true in the fragrance, cosmetics, and nutraceutical markets, where design and packaging add value to the product."
Difficult defect detection
Saint-Gobain produces more than 30 billion bottles and jars per year for the food, perfume, and pharmacy sectors worldwide. With five furnaces running around-the-clock, Saint-Gobain's La Granja plant supplies roughly 15,000 tons of cosmetic and perfume bottles annually to some of the biggest names in the beauty business, from designers like Carolina Herrera, Paco Rabane, and Spain's own Agatha Ruiz de la Prada to mass market companies like L'Oréal and Coty.
It was to satisfy this last customer, Coty, that La Granja first encountered the need for additional inspection. In the summer of '01, the plant was working on a large order for nail polish bottles?30 million per year?to be marketed in the Far East under Coty's Margaret Astor brand when occasional traces of mold dope, the lubricant that helps newly formed bottles slip out of their molds, started to appear on the 11-mL containers.
"The challenge with this nail polish bottle is that it is very sharp around the shoulders," says Sonia Herguedas de Diego, who heads development on the glass line's cold end. The angular edges mean that the corners of the mold must be heavily greased to facilitate the release of the molten glass. "The mold dope defect is directly related to how smoothly the gob?molten glass?transfers in and out of the blank side of the mold," Herguedas adds.
The mold dope stain, although miniscule and appearing on perhaps just one in 350 bottles, constitutes an unacceptable flaw, especially in view of the notoriously stringent standards of the Japanese market. This defect is so serious, according to Herguedas, that if at the end of the line one or two containers sport traces of mold dope, it's enough to turn a pallet of 60,000 bottles back into cullet; crushed glass that gets recycled into new bottles.
The bottle manufacturing line has two other inspections systems, besides the COSMOS. Bottles first pass through a custom-built inspection system, which looks for tiny cracks in the finish area. Then, an Emhart-Powers dual head gager verifies that the bottle opening is the right size and functions correctly.
Finding the flaws
In the search for a machine to sort out unacceptable bottles, Saint-Gobain found AGR's new inspection system especially well-suited to the job. "Typically, vision-based sidewall inspection targets non-surface defects," explains Marta de la Torre, the AGR's regional sales manager who supports the La Granja facility. "Our system does the reverse, emphasizing surface defects, whether they are mold dope stains or things like lap marks, washboards, or orange peel defects." The inspection unit can check up to 300 bottles/min, PD is informed.
The Windows NT™-based inspection system allows operators to view and select menu options through a keyboard.
The core of the inspection system is newly developed, proprietary illumination technology, which manipulates light to bring out the defects that are surface-oriented?as opposed to those embedded in the product. A combination of special filters and lighting techniques checks for flaws that render bottles unacceptable.
"Nail polish bottles are small," Jiménez comments. "We found no other equipment on the market that could inspect for such small defects in this size container while being versatile enough to do big containers, too. Many of these defects are not visible to the naked eye."
La Granja installed the inspection system on one leg of a perfume bottle production line in September '01 and the second unit arrived, and was set up on a parallel segment in May '02. "We told Coty about our machine purchase and the new inspection capability," says Herguedas. "Since then, we have had no reported claims or problems." The system's inspection results have even become a benchmark for a new warranty agreement with customer L'Oréal.
Along with solving the mold dope problem, the inspection system has other capabilities that make it interesting to Saint-Gobain, chief among them its versatility. One of the major challenges with fragrance and cosmetic containers is the plethora of unique shapes and unusual decoration. For instance, with a storehouse of 1,500 molds, Saint-Gobain churns out a wide assortment of glass bottles, and a single line can easily produce two or three different containers a week.
This lack of standardization makes it very difficult to develop a common inspection routine to cover the almost-infinite variety of container configurations. In addition, because the market places a premium on inventive design, the conventional squares and circles typically used by vision systems to define an inspection region can limit the available inspection area, preventing a comprehensive examination of most bottles.
But these constraints are not an issue with this inspection system. Aware of the market's rigorous quality criteria and penchant for novelty, AGR responded by devising adaptive inspection regions, a new feature that allows inspection to conform automatically to the shape of the container or targeted region-of-interest. This approach to viewing container shape permits inspections to be refined for specific applications or recurring defects unique to a specific bottle design.
The region-of-interest feature is further enhanced by incorporating adjustable sensitivity controls. Different defect sensitivity zones within a single container can be set up to provide the appropriate level of defect detection according to the application or the customer. These multiple, operator-configurable zones can be adjusted independently for maximum defect identification, allowing inspection to the finest detail to meet the most discriminating requirements of the cosmetic market.
Another technique used to enhance the inspection system's viewing accuracy for complex bottle shapes is edge-shadow compensation. The combination of thick walls and non-traditional design can produce shadows around the edges of some containers, triggering sensors to register a flaw, PD is told. The system is equipped with an imaging algorithm that distinguishes the shadows from actual faults within the inspection area, preventing false defects.
Changeover is a regular event at La Granja, with each line scheduled to produce several different container styles per week. "In the short runs of the perfume business, just one to two days per mold, you can't spend half a day on a job change or you'll lose money," says Jiménez.
Saint-Gobain has found that the inspection system actually helps smooth out the changeover process and accelerate the collection of good ware. On starting a new job, it takes a few hours before molds warm up thoroughly and production of acceptable bottles becomes consistent, says Herguedas. The ratio of bad ware to good right after start up can run as high as 80 percent, typically sending both perfect and imperfect bottles to cullet. By filtering out and rejecting only defective product, the inspection system allows good ware to accumulate much earlier in the manufacturing process. "We figure the inspection system saves two pallets with each new job," says Herguedas. "Plus it saves time. We get good ware one and one-half to two hours sooner than we did without it."
Also a significant energy savings accompanies this productivity boost. "Even though defective containers are recycled, every reject represents a waste of resources," says Teofilo Gangoso, production manager at La Granja. "The fewer bottles sent to cullet, the more efficient La Granja's energy use becomes."
Actual changeover entails no more than 15 to 20 minutes of mechanical and software adjustments. Once a job has been run, all the inspection parameters can be stored in the system and recalled for the next run.
A keyboard and monitor screen built into the face of the inspection unit make it easy for operators to view and select basic menu options. Statistical data can be displayed to provide process feedback, enabling factory personnel to respond proactively to malfunctions on the hot end. As a security measure, access to other levels of software control is password-protected, so setups and inspection parameters can not be inadvertently changed.
The inspection system is Windows NT™-based and facilitates remote diagnostics and troubleshooting. "If we have problems, AGR headquarters in the States can tie in to the machine by modem to check the light levels, the region of interest, and so on," Herguedas concludes.
At La Granja, glass container production for the cosmetic and fragrance markets run at a rate of 400 bottles/min for one line; altogether, the plant has 5 production lines. A container is shaped in a two-step process known as narrow-neck press-and-blow, which involves both a blank for preliminary forming and a final mold to give the bottle its exact contour and decorative pattern, if any.
After shaping, the new containers spend about 90 minutes on an annealing lehr, where their temperature is brought back up close to the melting point and then reduced gradually to, approximately, 100 degrees F. The reheating and slow cooling eliminate the stress in the containers, making them stronger and shock resistant.
Once the cooling process is finished, the bottles are transported on an overhead conveyor that splits into two parallel segments, each of which is equipped with instruments for check detection and finish inspection. The COSMOS inspection system is installed on both segments of the line, and rejected containers are recycled back into the furnace.
The true beauty of these bottles is finally evidenced on retail shelves. The unique shapes prod retail buyers' curiosity and with these bottles, no surprises (bottle defects) should go undetected.
More information is available:
Glass bottles: Saint Gobain, 212/223-7100. Circle No. 414.
Bottle Inspection System: AGR Intl., 724/482-2163. Circle No. 415.
Bottle Inspection System: Emhart-Powers, 607/734-3671. Circle No. 416.
About the Author(s)
You May Also Like