Automated Quality Control: Within Spec
May 01, 2009
by Shane Whitaker
Processors can be assured the baked foods and snacks they ship should be free of contaminants, are within product specifications and consistent in appearance because of today’s automated quality control (QC) equipment. For many years, nearly every bakery relied upon human interaction with the product to ensure that its foods were of high enough quality to be shipped to customers, but now they can remove that subjectivity of individual inspection and rely on a variety of equipment to provide peace of mind.
Metal detectors, X-ray machines, checkweighers and vision inspection systems are more commonly found in all kinds of bakery and snack food plants to perform quality control checks on products at various stages in production. More companies are using automated QC systems nowadays, according to Vincent Feix, vicepresident and North American sales manager, De La Ballina, Pointe Clair, QC. “Some are using them just as information gathering devices,” he said. “Others are using them as integral parts of the quality control process to accept or reject a product.”
Terry Woolford, vice-president of sales and marketing, Smiths Detection, Alcoa, TN, observed, “Many of the major retailers are writing detection requirements into their quality and hazard analysis and critical control point (HAACP) programs. In order to sell products to most major retailers, some level of quality assurance is required, and many of the larger retailers are starting to want X-ray inspection of their products.”
Much of the growth in automated quality control systems has been with small food manufacturers that desire to grow and sell their products to large chain stores, according to Steve Mason, national sales manager of Fortress Technology, Toronto, ON, adding that the company’s metal detection systems comply with the quality expectations of the store’s potential customers.
Metal detection and checkweighers are the oldest and most common automated QC systems found in food manufacturing plants. Very few food processors today are willing to take the risk of operating without metal detection or other inspection systems, according to Kevin Jesch, manager of inspection systems, Heat and Control, Inc., Hayward, CA.
“In a bakery operation, for example, a processor might use metal detection for raw materials prior to introduction of the process to ensure the safety of a batch being prepared,” he said. “Metal detection might be used prior to key pieces of equipment such as a slicer, for example, to avoid potential damage to equipment. Finally, metal detection after packaging is essential as the last opportunity for contamination of the product.”
Heat and Control offers a full line of metal detectors, X-ray inspection systems and checkweighers. Its CEIA metal detectors are available as horizontal metal detectors for bulk or packaged products, a free-fall system with automatic reject valve for powdered or granular products, systems for pumped products and gravity metal detectors for mounting above form/fill/seal baggers for snack foods and other products.
CEIA introduced a new generation of metal detectors, the THS/ MS21 series. “In addition to offering the highest sensitivity possible, these detectors are self-monitoring and self-calibrating to make them more robust and reliable than anything else on the market,” Mr. Jesch said.
The CEIA THS/MS21 is continuously self-calibrating. “Special electronic stimuli are sent to the transmission and receiving chain of the metal detector,” he explained. “This causes variations in the detection signal that are transparent to the user but provide checks on the detection characteristics analogous to those obtained with manual transits of test samples. These are then compared with the reference values stored by the factory at the time of calibration to ensure accuracy.”
The new metal detector series also provides Bluetooth connectivity as a standard feature, which allows connection to a laptop for programming and monitoring, according to Mr. Jesch.
Fortress Technology’s Vector conveyor metal detector system can be built to customer specifications and provides an “all in one” solution for customers, according to Mr. Mason. The company’s latest technological advances are for the customer’s metal detector to act as a critical control point for HACCP applications, he noted. “This is accomplished by the use of Fortress’ CONTACT software,” Mr. Mason explained. “Data logging and wireless Ethernet capability make it easy to stay in contact.”
Whereas metal detectors are great at finding product contaminated with ferrous and nonferrous metals, they are not able to detect materials such as stones, pieces of glass or agglomerates. And if this is a concern for the processor, an X-ray machine can be added to its lines. X-ray inspection offers many advanced features including portion control, missing product detection, weight analysis and contamination detection all rolled into one system, according to Mr. Woolford.
Smiths Detection offers a broad product line of conveyorized X-ray systems to automatically handle, inspect and reject defective products. “Many snack food companies are using X-ray inspection as their endof-line inspection system for cartoned or cased product as a replacement, and upgrade, to metal detectors on their vertical form/fill/seal systems,” Mr. Woolford said. “X-ray inspection has a distinct advantage in this instance because it is not affected by most forms of packaging including metalized films and foils. By inspecting sealed product, a company can be assured the product cannot gain additional contamination as it travels down the production line and ultimately to customers.”
An X-ray system adds value to processors’ lines, and Mr. Woolford provided an example of its machines used on a line inspecting cereal products. “During the manufacture of most youth-marketed cereals, a sugar slurry coating will be applied to the cereal flakes or puffs. This sugar slurry can build-up quickly on manufacturing equipment and conveyors and form what looks and has the properties of a jaw breaker or sugar ball, also know as an agglomerate,” he explained. “Such agglomerates can cause damage to teeth and in general are a nuisance and source of customer complaints. The Smiths X-ray system detects and rejects the agglomerates, helping the customer to optimize its equipment cleaning schedules to minimize agglomerates produced.”
Heat and Control offers X-ray systems from Ishida, which has recently introduced two new models in response to market demands — the EA series for entry-level customers and the DK washdown series. “Sensitivity requirements are tending to require elimination of smaller and smaller contaminants for enhanced food safety,” Mr. Jesch said. “This trend will increase the implementation of X-ray inspection systems.”
LeMatic, Inc., Jackson, MI, uses a variety of automated QC equipment on its lines except X-ray machines at this time. LeMatic has developed the Auto-Eye vision inspection systems and has used these in combination with checkweighers and metal detectors to ensure its customers ship safe and high-quality buns and muffins.
In fact, LeMatic designed a line for a major customer that has two different types of vision inspection, according to Ray Anater, the company’s vice-president, new product development. The customer is using a vision system to inspect product as it exits the oven, removing product that could be problematic to downstream processing and packaging equipment.
Farther down the line, LeMatic implemented another vision system that performs three different inspections on each muffin. A top camera inspects the overall color of the product and also looks at the diameter and shape of the product, measuring precisely within a millimeter of accuracy, according to Mr. Anater. A 3D measurement is taken using a laser and cameras that look at the height and slope of the product to ensure it is within specification. Finally, the bottom of the product is inspected to make sure there are not any burn marks or blemishes, and all this happens at speeds in excess of 300 pieces per minute. If a product is out of spec, multiple air blow-off systems can remove the offending product; however, not all products rejected at this point are waste. The system uses multiple air blow-offs, so baked foods that may be within specifications but are upside down can be reintroduced to the line later by an operator, he explained.
The LeMatic-designed line also includes two checkweighers from Mettler-Toledo Hi-Speed and a Mettler-Toledo Safeline metal detector. The first checkweigher inspects product after the initial vision system, and the second weighs the product after it is grouped and packaged to ensure no product is missing in the final stage. The metal detector is also employed after packaging.
All of the QC systems are linked via an integrated communication network with a global recipe setting. All the operator has to do is let it know that its running a particular product, and it automatically selects or downloads the appropriate parameters at all the inspection equipment, according to Mr. Anater. These systems also collect data, which can later be analyzed and trended to improve the production processes.
Montrose Technologies, which acquired the Dipix product lines and business in 2008, has successfully implemented a wide range of automated vision inspection systems within the baking industry during the past 12 years that analyze object geometry and color characteristics in both the second and third dimensions, according to Geoff Evans, director of sales and marketing, Montrose, Ottawa, ON.
The success of a vision system is in taking advantage of its inherent ability to identify downward trends, according to Mr. Evans. “Our customers recognize that to be successful, plant personnel need to interpret real time or historic data and use the results to optimize the lines performance,” he said.
De La Ballina’s vision inspection systems are generally used for two purposes. First, they can be employed for processing, where the main goal is to collect comprehensive control data and statistics on makeup line, for example, and the data would mostly be used to adjust reactively process parameters and limit product waste in case of process drift. “If global line supervision software is in place, data collected from our vision inspection system can be used in a closed-loop principle to correct process parameters in real time,” Mr. Feix said.
Second, vision systems control final product quality. “In 95% of cases, these quality inspection systems will communicate and pilot a system to reject bad product based on criteria such as dimensions, shape, dissymmetry, topping presence and coverage, baking color and other baking defaults such as dark or light points, blisters, etc.,” he observed. “Numerous options for rejecting devices are possible, depending on product size, weight, fragility and density. Rejection criteria and tolerances are fully and easily parametered and come from customers specifications.”
EyePro Systems, Trento, Italy, can help processors to more easily analyze the large amounts of data being collected by its Q-Bake vision systems, according to Andrew McGhie, the company’s North American business manager. Many processors use these systems and their data to improve their processes. For example, he said if a company wants to have rounder tortillas, they can make changes to the formula and/or process and then objectively measure the results using a truly representative sample size of either 100% or at least a significantly larger sample size that is more representative than 12 tortillas every half hour. “I can really tell whether I have made the desired improvement,” Mr. McGhie said.
EyePro also added counting features to its vision systems. “Using the vision capabilities of the system to not only inspect and reject but also to count or align product will save labor in the process and help to create a direct payback for the vision system,” Mr. McGhie said.
QC in bakeries today should be greater than ever before, thanks in part to automated systems that can find and reject out-of-spec products faster and more accurately than possible by human intervention. These systems are bound to only improve and become less expensive for processing plants in the near future.