Machine vision is of increasing importance in the sphere of quality assurance and process optimisation. Flexible, economical and reliable inspection systems are key requirements for suppliers to the automotive industry. ˜While vision applications range from simple checking functions to complex tasks, quality control applications often challenge vision system suppliers as well as their system integrators. German integrator, Fuetec GmbH mastered a challenging quality assurance task using high-performance vision systems providing an important fuel injector supplier with a reliable inspection solution using In-Sight vision systems.
Fuel injectors for automotive engines have stringent precision requirements during production requiring a fully-automated quality control system. This mass produced item can only be checked economically if the visual inspection cell guarantees a high level of reliable inspection precision plus flexibility for the different types of engine at a high throughput.
The challenge
The engineers at a notable automotive industry supplier of fuel injectors in Homburg were facing this situation in production. They needed to detect a wide range of references for the different fuel injectors with reliability. They also needed to incorporate the solution into their quality management system to ensure complete product traceability through part identification by data matrix code. High demands were also to be made of the reliability of the visual inspection cell, as a three-shift operation, including weekends, had to be guaranteed.
Unified vision solution
Quotations were obtained from various system integrators for a new, fully-automatic visual inspection cell capable of handling the company's requirements. The concept proposed by German vision integrator Fuetec GmbH and their demonstration of its viability regarding the application requirements convinced the decision makers and the first of three visual inspection cells was installed in March 2006. As of October 2007, further expansion is in progress.
The visual inspection solution is based on vision systems from the Cognex In-Sight family including the 5100, 5110 and 5403. Five different In-Sight vision systems perform different aspects of the overall task within the inspection cell. For example, the high resolution In-Sight 5403 is used for maximum image resolution and the In-Sight 5110 for verifying and reading data matrix codes. As opposed to a purely PC-based solution, this is more flexible and reliable because each of the independent In-Sight systems can be replaced immediately on a 1:1 basis ensuring rapid reaction to any problems. The 5 In-Sights fitted to the inspection cell are all mounted on special precision mechanisms allowing them to be adapted to new tasks at any point with minimal set-up time. Some 32 different types of injection nozzle currently pass through two inspection stations, each containing five In-Sights. Within half a second, 25 different characteristics are detected and the results sent directly to the central control server. The parts are guided through the inspection station in a cycle of about 11 seconds. This means 1500 to 3000 parts per shift in 3-shift operation including weekends.
What does In-Sight do?
* Ensures that the groove on the nozzle tensioning nut has been formed exactly. With low camera resolution, the edge appears blurred giving inaccurate results. With the high resolution In-Sight 5403, results are reliable.
* Guarantees the angle position of the electrical connectors to an accuracy of 0,5°.
* Ensures the correct sealing of the protective cap and copper sealing disc.
* Verifies the presence of the correct nozzle tensioning nut.
* Vision tools from Cognex were a key factor in the solution proposed by Fuetec. In-Sight vision systems are equipped with the high-performance PatMax, a geometry-based vision tool for part recognition and localisation. As well as this, IDMax software can tolerate distortion and manage the most difficult contrasts allowing the task of reliable verification and reading of data matrix codes to be mastered, even in difficult inspection conditions such as oily surfaces, which can lead to reflections on the code.
Complete part traceability
Each part being inspected has an identifying code. These data matrix codes are permanently engraved in the metal using laser-etching, a DPM (direct part mark) method and measure just 4,5 x 4,5 mm. For 100% quality, read after write verification is required. This verification checks code quality using high-performance vision algorithms that are much more demanding than simple code-reading. A high read rate was a prerequisite for the vision solution. With high quantities of expensive parts, a difference in read rate between 98,8% and 100%, as in this case, represents a considerable cost saving. The data matrix codes also guarantee complete traceability of manufactured parts and the vision solution is fully integrated into the company's quality management system. Another plus is that the user friendly development environment in In-Sight Explorer proved beneficial, allowing a convenient user interface for programming vision tasks.
For this automotive industry supplier, the concept and structure of this complete vision solution from a single source has the additional benefit of standardised hardware and software components considerably simplifying the stocking of spare parts, improving reaction times and cutting costs.
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