Metal detection and vision inspection: The last defense
April 1, 2013
by Shane Whitaker
Today, bakers and snack manufactures rely more than ever before on automated systems to perform quality inspections. Manual inspections can be extremely expensive because of labor costs, and because quality checks can be subjective, rejected product can vary from operator to operator.
Guaranteeing all defects are detected, especially when it comes to food safety, is the biggest issue, noted Joe Crompton, director of software and controls, BluePrint Automation, Colonial Heights, VA. “Traceability, liability and company reputation all factor in when it comes to food safety,” he said.
Quality assurance equipment must be dependable, increase efficiency, adapt to changes and completely eliminate manual inspections and intervention, according to John Keane, executive product manager, post packaging and automation, AMF Bakery Systems, Richmond, VA. “These systems must consistently inspect every product made at full line speeds and reliably compare each and every product against a list of variables in their established minimum standards,” he said.
New school approaches
Metal detectors have been used in baking and snack processing longer than automated vision inspection. Their primary role is to ensure that no foreign metallic material is in products that reach consumers. Until recently, their primary role was at the end of the lines or as close to the end as possible. “It was seen as a sorting machine that would just remove the product that had metal, and you just kept making your product all day long,” said Steve Gidman, president of Fortress Technology, Toronto, ON.
However, he termed this the “old-school approach,” noting that processors today also install metal detectors upstream in the process after identifying hazards within their facilities. Employing metal detection systems earlier in the line allows processors to possibly prevent machinery damage. “This is a very big cost savings and is a way metal detectors can make you money,” he explained. “You can save thousands of dollars on maintenance.”
Mr. Keane pointed out that he has seen metal detection used to inspect raw material right out of the mixer, prior to packaging, after packaging and prior to loading into a shipping container.
Nonetheless, end-of-line inspection remains perhaps the greatest need, and the Food Safety Modernization Act (FSMA), which requires food processors to implement HACCP-like programs, has identified metal detection as an area of great importance, according to Geri Foley, metal detection sales manager, Mettler Toledo Safeline, Tampa, FL. “The ability to detect and confirm rejection of a contaminated product is a critical component,” she said.
TNA North America, Coppell, TX, partnered with Safeline for the new Intelli-detect 5 metal detectors used on its high-speed vertical form/fill/seal machines, capable of making up to 135 1-oz bags per minute, according to Mark Lozano, sales manager. The machine matches the chute configuration of the bagger to improve product transfer and speeds through the system, he said.
Because of new food safety requirements, Mr. Lozano said, the company increased the sensitivity of the units so they can pick up smaller nonferrous or ferrous metal particles. The company offers several options for actions when metal is detected. For example, the bagger can make a double-long bag so it is easily identified and removed. It also installs automated systems to blow off the rejected bag. It can set off an alarm or halt the bagger, but most operations don’t want to have to stop the machine during the middle of production, he added.
False rejects and reliability are primary concerns. Therefore, when inspecting items such as tortillas, product effect losses and delays because of their moisture levels can result in significant unnecessary costs, noted Todd Grube, manager of inspection systems, Heat and Control, Hayward, CA. Thus, he said, CEIA invented multi-spectrum technology to eliminate product effect rejects while maintaining the highest sensitivity levels.
Testing made simple
Metal detectors and vision systems must be useable and maintainable by typical operators, Mr. Crompton said. “Easy to teach, calibrate and operate are often challenges with some of the newer technologies,” he added.
Because meeting stringent detection levels for all metals is increasingly important, Mr. Grube said CEIA 21-series detectors feature continuous auto-testing and self-calibration to ensure optimal detection accuracy.
Fortress offers automated testing and record keeping of results, which is especially beneficial in snack manufacturing plants, Mr. Gidman said. This allows processors to more frequently test metal detectors with little or no cost involved. “A manual test, depending on access to the detector, can be quite expensive, and if you have a lot of them in your plant, it starts to multiply quickly,”
The company also offers HACCP- and FSMA-compliant software on its Stealth metal detection systems, with plug-and-play application. Reports can be generated by production line, time period or type of event and are easily exported to Excel or PDF files.
EyePro Systems, Kansas City, MO, will integrate metal detectors with its vision systems to give companies two levels of control, according to Andrew McGhie, business manager. Yet these will often include two different rejection systems so that bakers can reuse product rejected for being visually unacceptable but permanently reject product contaminated with metal.
Vision-based inspection systems continue to become more sophisticated with expanded capabilities. For example, EyePro provides vision systems to detect multiple toppings on a product such as a pizza. Such systems also can ensure pepperoni, mushrooms and peppers are uniformly distributed while counting the slices of pepperoni so that the product also meets consumer expectations, Mr. McGhie said.
Because of pizza’s high value, manufacturers also can perform inspections at multiple points on a line. So rather than rejecting a completed pizza because it has an out-of-spec base crust, a processor might have an inspection point set up after the crust is formed. A second camera can monitor it after the sauce has been applied and yet another after topping with cheese, meat and vegetables.
Decreasing costs and increasing performance of vision represent the biggest advances with these systems, allowing bakers to invest in technologies that were cost-prohibitive just a few years ago. “Things such as X-ray, multiple cameras including color and other types of imaging allow better inspection of products,” Mr. Crompton noted.
Vision inspection today offers higher precision and keeps up with faster line speeds, said Stephen Dyer, product manager, Mettler Toledo CI-Vision, Aurora, IL. “Every year new capabilities get added, similar to the way that PCs and processing power has increased,” he added.
CI-Vision’s primary focus relates to packaging, ensuring that codes are printed on individual packages correctly and are readable. “This can assist with a recall, if needed,” Mr. Dyer said. “It also gives consumers the information they need to know whether or not what they are consuming is safe and ensures labels are consistent for allergens.”
De La Ballina Industry, Lachine, QC, offers vision inspections for process as well as final quality control. Its process systems can collect comprehensive control data and statistics on makeup lines for example, noted Vincent Feix, vice-president and North America sales manager. “These data would mostly be used to reactively adjust process parameters and limit product waste in case of process drift,” he explained, noting that it could also be used in a closed-loop to correct process parameters in real time.
Final product quality inspection systems, Mr. Feix said, will communicate and pilot a system to reject “bad product” based on criteria such as dimensions, shape, dissymmetry, toping presence and coverage, baking color and other baking default such as dark or light points.
Generally, bakeries invest in vision inspection and rejection equipment to eliminate waste and labor, noted Patrick Goche, general manager, Forpak, Burnsville, MN. The company recently added a vision reject system that can be used prior to its stacking equipment to remove products that are not in spec. “Everybody is trying to find a way to cut their costs.” Mr. Goche said.
Bakers and snack manufacturers can use vision inspection to detect color, size and shape of post-baked product as well as cripples, Mr. Keane noted. Vision systems can correct product orientation, spacing or alignment prior to a process that requires consistent presentation or even distribution. They also can be used to divert product flow from one main feel line to multiple lines prior to packaging, he noted.
In the post-packaging area, vision inspection can determine if the correct loaf count was loaded into a shipping container. It also can verify bags are being placed in the correct shipping container. “In a vision application, we used a vision sensor to read the bar code on the bag prior to loading into a container,” Mr. Keane explained. “The data gathered can also verify the number of filled bags produced for a specific bar code/bag type.”
To further reduce labor, EyePro can establish vision systems with feedback loops to automatically adjust oven burners to ensure products such as cookies are kept with acceptable color ranges, Mr. McGhie said. The technology has been applied in automated feedback loops to adjust tortilla presses. The system can be set up immediately following the press to ensure tortillas are at an acceptable diameter, and if not, it can signal adjustments before too many products are made that fall out of spec.
Because the tortilla inspection system only looks at the diameter size, it can employ less expensive black and white cameras. The feedback algorithms used to keep products consistent represent the most critical parts of these vision systems, Mr. McGhie added.
EyePro also can integrate its inspection systems into pick-and-place technology, and out-of-spec products simply are not picked up by the packaging robots.
Eyeing the future
The future of metal detection, according to Mr. Gidman, includes smaller systems that fit into tight spaces as detectors move further into process monitoring. “We are going to see applications that we never saw before,” he said. “We are not compromising performance but focusing on the detector becoming more of an indicating device, guarding the health of the process rather than acting as the policeman at the end of the line.”
Today is an exciting time for process integrators and developers because of all the new metal detection and vision equipment. “Implementing these technologies in a cost-effective and robust manner will provide many challenges but also many rewards for those willing to take it on,” he added.
Looking ahead, Mr. Keane pointed out that challenges with vision inspection, metal detection and X-ray systems will be to perform at higher production rates, to be flexible enough to handle a greater variety of products and to achieve a higher level of detection capability based on increased standards.
Mr. Dyer said the future is about greater automation, and machine vision is well-positioned to assist bakeries and snack food manufacturers to meet production and quality needs.