Testing and Evaluation Improve Product Quality for Manufacturers

When you manufacture aircraft engine parts, product quality is more than just a competitive differentiator—it can be a matter of life and death. Having a real-time testing system that automatically measures product quality parameters and then turns that data into a direct feedback loop that influences production systems can be a tremendous asset.

AV&R Vision & Robotics (www.avr-vr.com) makes industrial automation systems for large original equipment manufacturer (OEM) jet engine companies, including systems designed to help the OEM client ensure substandard parts don’t make it off the shop floor and into the OEM’s engines. One of the Montreal, Canada-based company’s principle offerings is a part finishing and inspection system which uses a six-axis robot and smart camera system from Austin, Texas-based National Instruments (NI) (www.ni.com) to examine turbine airfoils following the deburring process.

“In the past, operators inspected and deburred different complex and high-precision turbine airfoils using deburring tools to finish the parts and then manually inspected the airfoils to ensure the parts were within specified tolerance,” explains Michael Muldoon, business solutions engineer, AV&R Vision & Robotics. “We developed a cell that can automatically perform these two processes, ensuring every part leaves the cell with the desired quality.”

After loading the part into the cell, a robot presents it to a deburring station that removes all of the burrs from the root of each airfoil, breaks each edge, and creates a radius on specific edges as per the drawing specifications. The part is displayed to an NI 1722 Smart Camera for inspection to look for surface defects such as nicks, dents, scratches, and tooling marks on the critical surfaces. The defects are classified according to their shape using particle analysis tools in the NI Vision Development Module. After inspection, properly deburred parts are moved to the next production stage while those that fail inspection are removed. The feedback mechanism is integrated into the workstation and thus has an immediate impact on production.

AV&R developed the unit’s human machine interface (HMI) system with NI’s LabView, which allows the operator to quickly understand the status of the system, the part under inspection, and the statistics of each part—including its serial number—as it is processed.

Testing is critical
According to Mike Lochaas, a marketing manager with industrial platform provider Advantech (www.advantech.com), Milpitas, Calif., measuring, testing and assessing your process is a critical part of any quality control system. In fact, carrying out these activities provides an important underlying foundation that influences not only the quality and consistency of your products, but the efficiency of your production process, your maintenance schedules and your product genealogy programs. Every system that needs production data to function relies on some kind of feedback loop and most of them have some bearing on product quality.

Jan Pingle, a product manager with Milwaukee-based Rockwell Automation (www.rockwellautomation.com) suggests there are two primary ways to inform a product quality feedback loop with the data it needs to influence operations. You can either run in-process data collection with automated devices, or you have to go out of process and take samples that are then tested in a lab.

“The typical in-process approach involves a standard historian,” says Pingle, adding that a historian collects data about your manufacturing process and then makes it accessible and understandable to plant floor operators so they know what decisions to make to ensure the smooth running of the operation and the consistent production of quality goods. “That’s the whole idea behind a historian. You measure what happens in real time. Then you load it into an HMI and people can use that to identify problems and make changes.”

>>Read this application story on how a major nutraceutical manufacturer addressed labeling errors.

The Milan, Italy-headquartered Luxottica Group (www.luxxotica.com) is another case in point supporting the broad impact appropriately collected and utilized product quality data can have on the business. Luxottica designs, manufactures and distributes fashion, luxury, sport and performance eyewear. The company’s house and license brands include Ray-Ban, Oakley, Bvlgari, Burberry, Chanel, Dolce & Gabbana, Donna Karan, Polo Ralph Lauren and Versace. Unlike AV&R’s aerospace clients, lives are not at stake if a sub-par product escapes from the production line, but the damage such an event could have on a company that differentiates itself with the highest quality eyewear on the market (and pricing to match) would be significant.

When Luxottica went looking for a new manufacturing control system that would provide improved visibility into production operations, improved overall equipment efficiency and—ultimately—improved quality, it selected FlexNet from Long Beach, Calif.-based Apriso Corp.

“Quality Control (QC) was being done visually by assembly-line workers, which was time consuming and inefficient,” says Andrea Gallina, plant manager at Luxottica’s Lauriano, Italy facility which produces 70,000 lenses each day and manages more than 350 distinct designs. “We needed to reduce our reject rate to improve our QC process and reduce this cost.”

Getting it right
A pair of Oakleys, which can cost as much as $400, can be highly customized, with plastic lenses offered in a dozen colors. Getting the difference between “Iridium Ice” and “Persimmon” right starts when the raw materials are mixed with a precise combination of pigmented ingredients to produce a specific colored lens for each unique batch. Once the correct color is achieved, plastic is molded to create the required shape. The lenses are then treated with various finishes, subjected to more than 20 quality control examinations, and packaged for shipment to an assembly plant.

Automating and standardizing critical processes—such determining lens color, shape and finish, which is now a fully automated process—has had a tremendous impact on Luxottica’s profitability, says Gallina; in the past, production and waste volumes were estimated. “Not only do we now have complete visibility and control over every stage of production, but we can also see details about our operations for any given phase or time frame,” he says. “We can monitor, trend and analyze specific areas or machines for continuous improvement and best-practice enforcement.”

Key performance indicators (KPIs) such as waste are monitored and reported by machine and operator, identifying trouble spots on the line that can be addressed before they become significant issues. “Our production processes are now done in a more controlled environment, helping to reduce the likelihood of rejecting work in process,” explains Gallina. “QC is still done by the workers, but now those workers have fresh eyes and vastly simplified jobs. Best of all, our QC is now cross-referenced with production and scrap reports, ensuring 100 percent accuracy of products leaving the plant.”

The impact of embracing this type of QC program has been felt beyond the wall of the Lauriano facility. With the increased reliability of product quality coming in the door, assembly plants have been able to eliminate their own QC inspections and reduce overall time to market. “(Today), we can clearly see and manage our production and quality processes in real-time, which have resulted in improved productivity and greater manufacturing excellence. We estimate our production volume has doubled with higher quality and less waste,” Gallina boasted.

Quality issues in the food industry which affects consumer health are different from, yet quite similar to, the world of sport and fashion, although perhaps not quite as dramatically as you would see with a defective aircraft engine.

Watching milk dry
The Murray Goulburn Co-operative (www.mgc.com.au) is Australia’s largest milk processor and one of the country’s largest exporters of processed foods, turning 35 percent of the nation’s milk supply into products.

Powdered milk is a core ingredient in a wide variety of staple foods—from chocolate to bread to baby food—but there is more to powdered milk production than merely letting the liquid content evaporate. The process has to be precisely managed to maintain product quality parameters such as color, flavor, solubility and nutrition. In 2009 Murray Goulburn installed a system to automatically monitor and control the most critical and delicate part in the manufacture of powdered milk—the final drying stage.

Murray Goulburn’s facility near the village of Koroit uses four dryers to process skim milk and whole (full cream) milk into a variety of dairy-based powders. Each dryer consists of a steel chamber standing up to six stories high and 20 meters in diameter. The milk—which has already gone through an evaporation process—is sprayed through the top of the dryer as a fine mist. Swirling air, which can reach up to 220 degrees C, removes the remaining moisture leaving a small particle of milk powder about the size of a dust particle. As the droplets fall, the air cools to about 65 degrees C. The powder accumulates on a static fluid bed and then exits onto a series of vibrating fluid beds. Powder from the fluid beds is sifted in a funnel-shaped hopper from which it is conveyed to the packaging area. Approximately 13 kilograms of whole milk powder or 9 kilograms of skim milk powder can be made from 100 liters of whole milk.

According to Geoff Rome, an automation and utilities engineer for Murray Goulburn, one of the crucial variables that affects the quality of the powder is its moisture content. Depending on its end use, the powder should contain between approximately 3 to 6 percent moisture. The key to achieving the right moisture level is to control the temperatures of the air entering the tower, the static fluid bed, and the vibrating fluid beds.

In the past, Murray Goulburn operators took hourly moisture samples and manually changed the temperature setpoints to control throughput and moisture content. However, the hourly interval was too long, especially given the importance of the moisture balance in the powder. Tests showed the moisture would often vary by as much as 0.3 percent, which not only had a negative impact on product quality, but caused equipment problems such as blocked dryers. When these would shut down, the result was wasted resources and reduced yields.

“We knew we needed an automated system to reduce the moisture variability of the powder,” said Rome. “Our goal was to find a solution that would help us maintain consistent quality while increasing final product throughput.” Murray Goulburn opted for a solution from Rockwell Automation which continually collects data from each dryer and utilizes predictive models to calculate optimum temperature setpoints for controlling and maintaining the desired moisture level during production.

Specifically, the system uses sensors to provide in-line, inferential quality measurements and facilitates real-time and frequent control feedback. Several factors that affect drying efficiency are tracked and managed, including variations in the milk solids concentrate as well as incoming air and humidity. Rather than requiring an operator to manually check the drying process every few minutes, the system automatically collects data inputs every 15 seconds, resulting in a significant reduction of moisture content variation. Once every hour, a physical sample of the powder is analysed with an infrared spectrophotometer to confirm the model. The results are sent to the modeling system where adjustments are automatically made if necessary.

Impact beyond goals
Like Muldoon and Gallina, Rome credits his new system with making a impact that goes beyond the product quality issues initially targeted. Lower moisture variability means the average moisture target can be increased without compromising product quality. This translates to higher yields produced from the same milk solids, increased dryer capacity and reduced energy usage.

The new system made it possible to reduce moisture variability levels in each dryer by an average of 52 percent—exceeding Murray Goulburn’s 35 percent goal and resulting in the production of an extra tonne of powdered milk product per day across its four dryers. “Those extra tonnes of powdered milk out the door made the investment in the solution well worth it,” Rome said. “Our reduction in energy costs has also contributed to the ROI [return on investment] of five to 10 percent.”

AV&R Vision & Robotics (www.avr-vr.com)

Luxxotica Group (www.luxxotica.com)

Murray Goulburn Co-operative (www.mgc.com.au)