Nondestructive testing relies on X-ray, IR imaging for product integrity
When manufacturers need to verify the structural integrity of a component or measure a specific characteristic of an object, they turn to nondestructive testing (NDT). While more than a dozen NDT techniques exist, machine vision companies are adapting their offerings with two subsurface inspection and evaluation methods in particular—industrial radiography and thermography—to reflect the realities of the modern manufacturing floor.
Diagnosing problems with X-ray
Industrial radiography, which utilizes X-ray imaging, has been employed in NDT applications for more than a century. Although the fundamentals of radiography have remained the same over the years, advances in image resolution, scan speed, and detection of smaller defects are making the technology increasingly attractive across a range of industries such as electronics inspection. The X-ray detector inspects for imperfections in components such as wire bonds inside an integrated circuit package and ball grid arrays, a type of surface-mount packaging that uses solder balls placed on the printed circuit board.
"In general, X-ray is growing as a market because more and more manufacturers are using X-ray inspection as a means of process and quality control," said Thorsten Achterkirchen, vice president of X-ray imaging for Teledyne Dalsa. "In some cases, the market is also shifting from traditional image intensifiers to digital flat-panel detectors."
Teledyne Dalsa has also identified a growing demand for portable X-ray systems, particularly for safety-based inspections. "If you look at the oil and gas market, for example, every weld in their pipeline has to be inspected to ensure it’s structurally sound, or they need to identify something that could cause a rupture down the line," Achterkirchen said.
X-ray plays prominently in the automotive industry for safety-critical applications. Inspection includes aluminum wheels, tires, engine blocks, and air bags. But the industry is expanding its definition of "safety-critical." That means more opportunities for X-ray NDT, said Rahul Alreja, director of global sales and marketing for the industrial division of VJ Technologies. The company’s VJ X-ray division manufactures integrated X-ray sources and high-voltage generators.
"You can’t assess certain things in the lab environment," Alreja said. "It’s only when the car is out in the field do you understand what’s happening. As automotive manufacturers collect more data, they determine which components are more likely to fail and risk injury, and those are deemed as critical components."
Automotive original equipment manufacturers (OEMs) require their suppliers from all tiers to perform 100 percent inspection on the components they provide, Alreja added.
Feeling the heat of failure
Infrared (IR) thermography offers another way for manufacturing and other industrial segments to detect voids, cracks, and delamination in a variety of materials. IR maps or measures surface temperatures as heat flows through, to, or from an object.
"We have been able to continually reduce the cost of advanced thermography, and miniaturization has allowed us to build smaller, portable, lightweight systems," said Markus Tarin, President and CEO of MoviTHERM. In addition to portable systems, MoviTHERM develops laboratory systems for manufacturers who want to test out structural designs, as well as integrates its products into fully robotic automated work cells.
Thermography is emerging as an alternative to ultrasonic testing (UT), especially for NDT inspection of carbon composites commonly used in the automotive and aerospace industries. In solid carbon composite laminate, IR can penetrate about 7 to 8 mm below the material’s surface. UT, which uses high-frequency sound waves to detect flaws, has been the preferred technology for NDT inspection of these composites.
However, manufacturers are "Feeling the pinch in realizing that ultrasound isn’t suitable for parts with very complex shapes due to their radius, making it difficult to pick up the signal from ultrasound," Tarin said. "Or they may have very large structures where it becomes impractical to use ultrasound because the measurement time is too long."
Ultrasonic NDT requires a coupling agent such as water or air to facilitate the transfer of sound energy into the test subject, whereas a high-resolution IR camera "Takes one noncontact shot to get one measurement and therefore obtains much quicker results over a larger area," Tarin said.
Despite the technical advantages and dropping cost of IR imaging systems, thermography providers still face one major barrier to entry. Companies have invested in training and certifying their NDT personnel primarily in UT, but by introducing an alternative method of measurement such as IR technology, "They now have to bear the cost of retraining and recertifying their workforce," Tarin said.
Casting a wider net
X-ray and IR imaging system developers see a few paths forward to put more of these NDT technologies on the factory floor and in the field. Achterkirchen expects broader adoption of digital radiography for NDT as capabilities improve. "One thing I find exciting is the ability to build X-ray systems that can see smaller and smaller features, especially when you get in the area of computed tomography," he said. "Combined with advances in X-ray sources that have tiny focal spots, you can see some amazing fine details at the submicron level that haven’t been imaged before."
When it comes to thermography, the need for speed during the manufacturing process will ultimately drive implementation of the technology, "Because other methods, like ultrasonic testing, can’t keep up with throughput requirements that are ever increasing," Tarin said.
Tarin also pointed out IR imaging is not a one-size-fits-all solution. "Physics limits thermography to certain types of measurements and applications. Sometimes a combination of different NDT methods is required depending on the complexity of the part," he said.
Beyond traditional industry segments currently using NDT, consumer product manufacturers are beginning to look at instilling the process. Alreja attributes this development to social media trends. "Before, it was hard for one or two bad products to make a dent in your reputation," he said. "Now, if one person gets a bad part and they have a strong social media following, they can tweet about it, and then it goes onto the evening news, and all of a sudden the reputation damage done to a firm is massive. NDT can help protect the brand by preventing bad product from hitting the market."
While OEM customers in electronics inspection typically understand their X-ray imaging systems, Achterkirchen cites a lack of knowledge among system integrators in more general applications as a critical challenge in X-ray NDT. "We make the detector, another company makes the X-ray source, and somebody has to have the knowledge and experience to integrate these two together, pick out the right components for the application, put it into radiation safety cabinets, and then add the machine vision software that drives the whole system," Achterkirchen said. "That skill is not easy to find in the market today."
Achterkirchen advised system integrators to learn as much as they can about FDA regulations and other safety requirements, particularly related to the radiation aspect of X-ray imaging. The process of integrating an X-ray system for NDT and other inspection tasks "is more complicated than putting together a traditional machine vision system," Achterkirchen said.
Meanwhile, as manufacturing facilities and processes become more connected and automated while generating and analyzing increasing volumes of data, companies expect NDT equipment and service providers to fit into that mold. To anticipate its customers’ needs, VJ Technologies partners with universities and labs and reaches out to thought leaders "To leverage what each of us brings to the table in order to offer next-generation solutions," Alreja said.
X-ray and IR imaging for NDT may represent a sliver of the market share for machine vision, but makers of these components and systems continue to develop solutions to keep pace with evolving demands from manufacturing and industry for tighter quality control and greater throughput.
Winn Hardin is contributing editor for AIA. This article originally appeared on Vision Online. AIA is a part of the Association for Advancing Automation (A3). A3 is a CFE Media content partner. Edited by Chris Vavra, production editor, CFE Media, firstname.lastname@example.org.