Comprehensive inspection of automotive solenoid valve filter elements using Cognex line of sight cam

  Schaeffler is a world-renowned automotive parts supplier. It has long been committed to the R&D and production of automotive parts and industrial bearings, and provides key technologies for automotive engines and clutches. Automobile solenoid valves are important components of automobile engines and one of Schaeffler's main products. Among them, the filter is a key component of the automotive solenoid valve, and its quality directly affects the working performance of the automotive solenoid valve.
The automotive solenoid valve filter is made of plastic. In a fully automated line, the filter needs to be automatically installed on the filter element. The mesh size is 0.3mm. Before the use of vision technology, production inspection relied on manual visual inspection. Workers need to use a magnifying glass to carefully inspect various defects on the filter rings one by one, such as broken filter connections, damaged filters, scratches on non-grid areas, etc. This purely manual visual inspection method involves huge risks and consumes a lot of labor costs in the long term.
"In 2011, we had a large production department that was assembling a certain process of automotive cam phase adjusters. Due to manual assembly, workers frequently missed parts," said Schaeffler's production manager. In order to completely avoid this human risk, we began to consider using a vision system to monitor the assembly process."
Based on the leading position of Cognex vision technology in the industry, Schaeffler decided to use its advanced technology after consulting with Cognex's technical experts. vision system to carry out technical modifications to the production line.
At the scene, due to the particularity of solenoid valve filter detection, there are many challenges in applying the vision system. However, Cognex technical engineers and Schaeffler technical personnel worked together to easily overcome these difficulties relying on Cognex's powerful vision technology.
"For example, the solenoid valve filter is distributed in a circle. If you want to obtain its picture, you must use a line scan camera + encoder. We need a very stable mechanical mechanism to fix the solenoid valve filter element, and use motor rotation to obtain the picture," Schaeffler's production director pointed out, "If the filter element vibrates greatly during rotation or the concentricity is not good, the linear effect of the scanned image will be very poor." To address
this problem, technicians from both parties designed and selected a A specific mechanical structure is used to rotate the solenoid valve, and then an effective picture is obtained by scanning its entire circumferential surface using a line scan camera.
"After obtaining good pictures, we found that the grid of the filter is very fine. We require that the pictures taken by the line scan camera can clearly see the grid, so as to ensure that the defects of the filter can be detected. This is very important for the light source and lens. The adjustment is very difficult." Cognex technical engineer said, "In addition, the grid part of the solenoid valve filter is of different sizes. There are three types according to the area size, and they all need to be tested. This also makes it difficult for the camera to detect solved a difficult problem."

Cognex line scan camera IS5604-11 installation location
Therefore, Cognex technical engineers found the smallest grid as the positioning, and then performed image processing and analysis on the five grids in sequence. Not only should the connection parts of the filter be checked for breaks or scratches, but also parts other than the grid should be comprehensively inspected to ensure that the filter is intact.

One of the defects detected: filter defect.
In these types of defect detection, since the defects are relatively small and the requirements for image processing are very high, we have carried out Point Filter and Neighbor Filter on almost every place that needs to be inspected. Image preprocessing. We do all the work that requires customers to adjust in the user-defined interface, which greatly facilitates the operator's adjustment." Cognex technical engineer pointed out, "For the operator, they We don't need to understand the meaning of each step of the procedure. We only need to tell them what graphic ranges need to be set, how to set them, and what parameters need to be adjusted. If other camera systems are used, then the problem arises, the operator It is necessary to understand each tool and the purpose and operation methods of many parameters in the tool in detail, which greatly increases the difficulty of operation.”

Pictures obtained by line scan cameras
In addition, the powerful spreadsheet function in the Cognex vision system greatly simplifies the writing of complex programs. Schaeffler technicians have also used other brands of vision systems, but they found that these systems have no problem when implementing single-function tool inspection, and then once complex programs are written, "the writing is often not very messy and complicated. It is difficult to have clear logic at all, that is, it is impossible to realize the detection function perfectly. Cognex’s powerful spreadsheet interface makes programming infinitely free and infinitely possible. This is what we like about Cognex visual technology. "
The Cognex line-scan camera is the camera system with the best openness, the smallest size, and the most flexible system communication that we have used so far." Schaeffler's production manager said, "The smooth operation of the Cognex line-scan camera has made We thoroughly identified all inspection defects and selected qualified products, thus avoiding the important quality risk of missing parts." The successful
use of Cognex line-scan cameras has greatly enhanced Schaeffler's confidence in the quality of its products , "In the detection of the solenoid valve filter, the camera we use is very advanced. As far as I know, the same industry has not yet used cameras to detect the filter. This is also an important advantage of our products!" Schaeffler's said the production manager.
"Now, as the quality control in the production process becomes more and more stringent and the degree of automation increases, Schaeffler factories have a huge demand for visual technology. They not only need to use cameras to detect the presence and size of workpieces, but also need Effectively read and verify the QR code engraved on the surface of the workpiece, and even detect whether there are cracks and other defects on the surface of the workpiece." He finally pointed out, "This good cooperation with Cognex has expanded The application perspective of cameras used in factories has deepened the understanding of camera systems. In the future, Schaeffler will trust Cognex even more to help us solve more production risks and customer complaints.