Intelligent cameras with an eye for detail
Today's image processing systems are able – even without an image processing PC – to recognize complex errors that could previously only be discerned by the human eye. They also provide data that makes it easier to document and analyze production processes. A high level of integration makes the cameras used in these systems very easy to adapt to new requirements for measurement and inspection. It is therefore not at all surprising that more and more of the world's most innovative machine manufacturers are using integrated image processing systems to gain a clear advantage over their competition.
More than meets the eye – Real-time integrated vision
Incorporating intelligent cameras into a machine's architecture has recently become a whole lot easier. Thanks to the partnership between B&R and image processing specialist Cognex, intelligent Cognex In-Sight 7000 cameras are now available with a POWERLINK interface. The integration of the POWERLINK standard into the Cognex Connect communication package – and of the cameras into the Automation Studio development environment – makes it possible to incorporate image processing systems into POWERLINK networks and connect them to B&R controllers.
Equipped with POWERLINK interfaces, Cognex cameras are a seamlessly connected element of the overall B&R system. This integration reaches so deep that the user sees no difference between B&R components and the Cognex vision system. The camera's firmware and parameters, for example, come directly from the controller. Since standard Ethernet protocols can also just as easily be transferred via POWERLINK without impacting cyclic data traffic and real-time behavior, an extra Ethernet interface is not needed to configure the cameras (this is done with the Cognex's In-Sight Explorer configuration tool) or to call up images for documentation and analytical purposes.
Image processing and automation systems converge
"For us, the clear advantage of this integration is that, since our machines are already fully equipped with B&R controllers, POWERLINK is the only communication bus we need, which allows us to keep wiring to a minimum," says Wolfgang Jahn, manager of control technology at LIBA. "Combined with the fact that the bus is deterministic, this is one of the main reasons we opted to base our image processing system on In-Sight cameras with a POWERLINK interface. Customer recommendations further solidified this decision."
The move has strengthened LIBA's already excellent position among warp knitting machine builders around the world. The company's leadership was recently recognized when its new self-healing Multi Compact woven fabric was awarded the Techtextil Innovation Prize in the category "New technologies". This success did not happen by chance. After all, LIBA's declared goal is to identify industry trends at their earliest stages and offer the advanced solutions necessary to prepare their customers for tomorrow's requirements today.
Earlier detection and prevention of production errors
With the development of three new image processing solutions based on In-Sight 7000 cameras with a POWERLINK interface, LIBA has remained true to its successful strategy. The cameras ensure that production errors are detected earlier, which minimizes their negative effects. At the same time, they also make documentation faster and easier than ever before. One of the first to profit from this new technology is a well-known automobile manufacturer, who uses an enhanced warp knitting machine with multiaxial weft insertion to produce fabric that goes on to be processed into car body panels.
This machine cuts sections of carbon fiber tape from rolls and stacks them with the fibers in each layer aligned in a different direction. Two chains lined with pins hold the ends of the tape sections in place as they transport the 50 to 150-inch wide fabric through the approximately 35-meter long production line. The layers are then stitch-bonded together. Then the edge of the fabric is trimmed off. The final product is wound on a roll, while the waste that remains on the pins is vacuumed away.
Minimized waste for reduced production costs
Each of these transport chains is monitored by an image processing system at the front of the machine that detects not only bent, broken or missing pins, but also contamination. An In-Sight 7200 camera handles all image processing and evaluation tasks. When it detects an error, the machine's central controller is notified and the machine is stopped.
"In the past, machine operators or quality control personnel would find damaged pins more or less by chance," says Rainer Seuss, the engineer in charge of multiaxial technology at LIBA. "By that point, many meters of defective fabric had already been produced."
Vision system increases availability
Now, the image processing system reliably identifies damaged or contaminated pins after no more than a single cycle. This does more than simply reduce waste; it also generates added value. "When an error occurs, the operator no longer has to tediously search 80 meters of chain for the pin that is responsible," explains Jan Märtin, head of design and development at LIBA.
"Since a bent or broken pin is often an indication of a more general problem with the machine, reacting to them faster helps prevent subsequent damage or machine downtime." The bottom line is that the image processing system brings increased machine availability and process reliability.
Further improvements to process reliability
For LIBA's second image processing system, now found on every continuous weft insertion system, process reliability was more than a welcome side effect – it was the top priority. The particular challenge here was that the sum of tolerance values over a very long chain made it difficult to predict the exact position of a particular pin. The image processing system would have to ensure that a thread is inserted in each of the gaps between pins. An intelligent In-Sight 7200 camera measures the entry point of the thread in each gap.
The results are sent via POWERLINK to the machine's central controller. This allows the weft insertion system to correct its positioning in the next cycle to keep the thread within a 10 percent deviation of the center of the gap. "POWERLINK's real-time capabilities were absolutely essential for this type of positioning," says Jahn.
The new image processing system replaces the light sensor measurement system LIBA previously used for the continuous weft insertion systems. "The biggest problem with the old solution was that the contact-dependent light sensor had to sweep between the pins, making accidental collisions virtually inevitable." A collision would destroy the measurement system and result in machine downtime. "Thanks to the no-contact solution based on cameras, these problems are now a thing of the past," explains Märtin, clearly pleased.
Higher availability = Higher productivity
The third image processing system was developed to monitor the carbon fiber tape as it is fed into the machine. Depending on the width of the tape being used, one or more cameras are used to record the length and width of any gaps that appear in the tape. They also use the edges of the tape to calculate its width. If any of the measurements deviate from their specified values, an error message is sent and the machine is stopped.
The operator then decides based on the severity of the deviation whether to allow the machine to continue running or to have the tape automatically removed. smartvision GmbH, commissioned by LIBA to develop the camera software for the three image processing systems, design the lighting and optics and commission these systems on the machine, selected In-Sight 7402 cameras for the task. "These cameras can process images with a resolution of 1280x1024 pixels in just 30 milliseconds," says Jahn. "That's sufficient to provide the necessary measurement performance."
Offering minimum jitter and maximum performance, POWERLINK is the perfect choice for Ethernet-based industrial applications with hard real-time requirements. The POWERLINK approach to communication management prevents collisions and provides uncompromising determinism. This is what has helped establish POWERLINK as the go-to solution for the most demanding applications in a wide range of industries.
Sights set on future developments
LIBA has already made great leaps forward with regard to process reliability, waste reduction and machine availability. Yet the textile innovator sees no reason to rest on its laurels. "The flexibility and performance of these cameras gives us plenty of room for improved functionality and new features," says Seuss.
Recognizing this potential, LIBA has already upgraded the image processing system that monitors the tape infeed with an additional function that allows machine operators to create a log file containing the sizes and positions of gaps in the tape. This data can then be used to create error maps for further analysis by quality control personnel. "And we're not going to stop there," promises Märtin. "We have a lot of very interesting ideas in store for the future."