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Current Thoughts on Machine Vision Applications in the Container Industry
by Nello Zuech, Contributing Editor - AIA Posted 02/21/2005
The container industry was one of the first to embrace machine vision or its predecessor non-contact, electro-optical technologies. When the US made wide use of refillable bottles (during my lifetime maybe not yours), there was a need to assure that the returned bottles were clean and had no residue in the base before they were filled again. As far back as 1948 there were systems using scanning optics with a photomultiplier that assured the bottles were empty before being refilled. In the early 70s companies that supplied the bottles themselves like Ball and Owens Illinois developed some analog television-based approaches that essentially looked at changes from a referenced image for sidewall inspection. Powers (now part of Emhart) offered a finish inspection system.
Today there are machine vision systems that address the needs of all container manufacturers as well as fillers. In the case of glass there are systems that can monitor the hot end as well as the finished product to cull out any reject conditions: cavity identification, finish concerns, empty bottle state, sidewall, neck and heel concerns, birdswing, etc. At the fillers there are systems for pre-fill inspection to assure quality of bottle and overall condition in the case of refillable bottles especially (scuff marks, empty bottle, finish concerns, etc.) as well as post-fill to assure the container is filled to the proper level, a cap is present, a label is present, it is the correct label and that it is registered positionally.
In the case of plastic bottles one finds systems that can inspect the preform for dimensions, thread presence, etc. as well as the finished bottle for finish, neck, sidewall and heel properties. As with glass, post filled plastic bottles can also be inspected for fill height, label presence, correctness and registration as well as cap presence.
In the case of metal containers, vision systems can inspect can lids as well as the cans themselves for irregularities or unwanted appearance conditions inside and outside, dimensions, or to verify the presence and integrity of features such as coatings, seal compound. Systems are also available to inspect the deco on cans for graphics and color correctness. In the case of all post-filled containers one can find machine vision systems verifying the presence and correctness of date and lot codes. Vision systems are also employed to verify container count at the shipping container level.
An attempt was made to solicit input for this article from all known suppliers of machine vision systems addressing applications in the container industry. The following responded to our questions and what follows are their responses.
Dave Dineff – AGR International
Frank Mann – Insight Controls
1. What are some specific applications in the container industry that your company addresses with machine vision technology?
[Dave Dineff, AGR International]
- Our systems inspecting Glass Containers on-line include: sidewall and base for particulate and inclusions, sidewall and finish dimensions, sealing surface defects, cosmetic and subtle visual defects (mostly for pharmaceutical applications). We have vision-based systems in both the Hot End (Forming) and Cold End of Glass manufacturing plants.
- Our systems inspecting Glass and Plastic Containers offline in a laboratory include: Body and finish high-resolution dimensional measurements.
- Our systems inspecting Plastic Containers on-line include: sealing surface, neck and base defects and inclusions. These systems operate inside a Blow molding system and on an external conveyor.
[Frank Mann – Insight Controls]
- For Glass containers we produce a multi-purpose system that automatically measures beer and wine bottles for Flange, Knock-out, dimensions, thickness, mold code identification, and pressure. The system also measures corkage and push up for wine bottles. This system is called ‘‘ISIS’‘ and is sold to Glass manufacturing plants. It is placed between two lehrs at the Cold End and performs several dimensional tests automatically that were previously done manually every hour reducing labor and increasing productivity and efficiency. The system also feeds all of its statistical data back to the ‘‘Hot End’‘ for process control adjustments.
- For the Pharmaceutical Industry we provide a high-speed inline inspection system that detects micro-cracks in glass vials providing a 360-degree view of each vial with a system speed of approximately 2000 parts per minute. It also detects contamination and wrinkles in the label. This system meets all of the FDA Part 21 requirements.
- For the Plastic Container industry, we produce an inline high speed inspection system that detects the thickness and presence of Barrier Material inside a multi layer preform immediately after coming out of the injection system. This patented process does not require destructive testing or contact with the preform. It is capable of running at production speeds in excess of that required to be used with a new 144 cavity plastic preform press, and is designed to be mounted directly after the press. This system can also be adapted to provide additional inspections on the preform finish area.
- ICS has designed and produced a new high-speed multi-line print inspection system for plastic closures that fits inside the existing print system from Desco, Kase or Tampo. This system uses no additional production floor space and can view and reject each of the four separate print lanes coming out of the various print machines.
- ICS has for many years produced a high-speed in-line inspection system for plastic closures and metal crowns capable of inspecting the liner area and consumer side for defects in excess of 3400 parts per minute.
2. What are critical machine vision system performance criteria for each of the applications that you address?
- For the glass industry, dimensional measurements are critical or the glass bottle will not stand up under the pressure of its carbonated contents. Looking for Flange and Knock Out are also important. This is caused when excess glass forms outside the mold edges causing rough areas preventing the bottle from sealing and in some cases risks of injury to the consumer. Because these things are inspected at the cold end of a glass plant it is important to get this information back to the hot end for process control changes before too many defects are produced.
- For the Pharmaceutical Vial application I mentioned, cracks in the glass container were going un-noticed because of their small size, but worsening as time goes by. Since the vial contained a controlled substance that was soy based it was 1) dangerous to the touch when it leaked, and 2) would spoil when exposed to air.
- Plastic containers are making major in roads where only glass and cans once were used. However there exists a problem when bottling carbonated drinks in small single use plastic containers. Their shelf life is greatly reduced. One process to prevent this is, is to add a barrier material inside the multi-layer preform that resists carbonization leakage and the ultraviolet of sunlight. Unfortunately the material is clear in color and very difficult to verify that it is present and in the thickness required to provide adequate protection. The new ICS system can do this at production speeds making this new process viable and allowing cost effective single serving plastic containers to enter the market.
- While printing and color issues have long plagued the plastic closure market, adding an in line inspection system on the end of an already large printing machine in most production environments was very difficult. There was simply no space available. This new system provides the needed inspection and process control statistics and requires no additional floor space.
- If the liner in a plastic closure is cut, deformed, wrinkled or contaminated, it will not provide an effective seal on carbonated drinks. The newer single piece liner-less closures must have strictly controlled dimensions in order to produce a good seal since they no longer can rely on the liner to cover up defects in the preform finish area.
- On-line it tends to be a relationship between throughput and defect size. Requirements for smaller defects while not exceeding specific false reject criteria are common. Laboratory is based on repeatability, reproducibility and the precision of the measurement.
3. What changes have been taking place in the technologies that are the basis of the machine vision systems used in the container industry that has resulted in improved performance?
- Higher resolution cameras at pricing that meets the industry cost targets. In addition, smarter vision components at speeds that permit in-line capability.
- Laser micrometers were used to make dimensional measurements, and are used today, but improvements in telecentric lenses and digital cameras now make it easier and faster to do the same measurements with machine vision-based techniques.
4. Where do you see breakthroughs coming in the specific technologies that are the basis of machine vision systems used in the container industry that will result in further improvements in the near future - next three years?
- With the improvements in cameras, lenses, and lighting techniques available today, the many complex and repetitive inspection tasks can now only be performed by a machine vision system. However, with the production speeds required, improvements in the product handling area have lagged behind. Methods of singulation, product rotation, and minimal contact are required but cannot sacrifice production speed.
- Unclear at this time -- costs are definitely a driver here. Mostly a low-end price market. Vision has almost become a commodity market where price is king. Very few opportunities to differentiate.
5. Are there market changes in the container industry that are driving the adoption of machine vision?
- Speed of production grows so does the need. Human components cannot keep up with the faster rates demanded and statistical control misses too many. Also, automation in all forms continues to be the demand to help lower production costs.
- The introduction of single serving plastic containers for carbonated drinks and beer will continue to convert many can and glass applications and open up new markets that are emerging. These new containers require some sort of inspection for the barrier or coating material that is used to extend their shelf life.
- Lower costs for single serving drinks in plastic are driving closure manufacturers to develop single piece liner-less caps at lower costs. This puts greater importance on a good sealing surface of the bottle preform requiring inspection for uniformity.
6. How will machine vision systems have to change to meet emerging applications in the container industry?
- They will have to keep pace with the production speed on newer plastic presses that offer 144 cavities or more.
- They will have to be fully automated contributing to labor reduction.
- As they proliferate, multiple systems must be linked together providing a complete statistical picture of how a production plant is operating. They should also, in conjunction with the plants data acquisition system, provide real time process control data.
- Price and capability in an inverse proportion. Price must fall while capability goes up.
7. As a supplier of machine vision systems for the container industry what are some challenges you face in marketing machine vision systems?
- As low-end systems tout solutions many customers rush towards the price. However, almost all of these applications fail (or fail to meet expectations) and the bad taste left in the customer’s mouth lingers. The more fully developed solution with support becomes more difficult to market. We have to look for product differentiation. If none can be achieved then we have walked away from applications.
- Providing complete system solutions that include handling, vision, and statistical data control loops. Some companies conclude that with the recent advances in digital cameras talked about in trade publications, this alone is the solution to their problem. Acquiring the image in a vision system is only a part of a complete machine vision system solution. Again as production requirements go up in speed it is now the handling aspect of a vision system that is the limiting factor.
8. What are your thoughts on the future of machine vision in the container industry?
- As companies face competitive issues and growing demand for new container applications, tireless, consistent, and accurate vision inspection will increasingly become a part of the production environment.
- It will continue to become a more commodity-based market with limited success in these low-end segments. This mentality will also put pressure on higher-end applications and may cause some segments of the industry to reduce their efforts because reasonable margins cannot be maintained.
9. What advice would you give to a company investigating the purchase of a machine vision system for a container industry application?
- Look at the supplier closely. What level of support and engineering capability do they bring to your needs? Do they understand your process? Have they worked in your industry before? Can they meet the needs of an entire organization or are they just a local or regional supplier? Also, do not be fooled by magazine ads for low price. What costs will you internally have to absorb to make you application successful? These are often hidden costs and if the personnel in the plant change then it usually means the application will suffer.
- Select a company that can provide a total vision system, one that includes all of the handling, vision, lighting, reject, and measurement capabilities. Also look for a company that develops its own adaptable software rather than relying on limited canned solutions, and finally, look for a company who has the ability to provide the after sale technical service.
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