QMT Features: November 2011
Error-free vision
Ensuring it always has a clear view across all manufacturing processes, German engine block manufacturer Fritz Winter Eisengiesserei uses a vision system for product traceability.

One of the absolute key factors in supplying components to the automotive industry is traceability. In virtually no other industry is so much value placed on being able to trace supplied parts all the way back to their source. High product expectations are reflected in the high demands of the quality assurance process.

That is a major reason why engine block manufacturer Fritz Winter Eisengiesserei GmbH of Stadtallendorf, Germany recently procured an intelligent vision system from Visolution GmbH to ensure it always has a clear view across all its processes. Using Cognex VisionPro vision software, serial numbers are detected without error and the company ensures complete product traceability.

On the factory floor, robot arms the height of a man lift engine blocks through the air as if they were made of polystyrene, moving the 60 kilogram (132.3 lb.) gray-cast components at a rate of one per minute. Sparks fly as high-tech milling machines cut the four-cylinder blanks into to shape in a matter of seconds. The result is a perfectly machined product for the car manufacturer to install in its high-tech power unit. Sixty kilogram steel engine blocks are light compared with those produced in prior years, yet the global automotive industry is demanding even lighter and more technically advanced castings. State-of-the-art engines made of high-performance steel have long since overtaken aluminium blocks in terms of weight, power, and low noise.

Precise component traceability
As so often happens in modern-day industry, customer requirements are steadily changing the manufacturing methods employed at the Fritz Winter plant. In response to demands for lighter weight engine blocks, the engineers at Fritz Winter Eisengiesserei need to be continually devising more intelligent technical solutions, both in terms of products and production processes. New innovations routinely increase requirements in terms of product quality. Limits and allowable tolerances are becoming tighter. Quality testing networks are becoming more integrated. Over recent years, this has helped minimize component defect rates.

For this long-established business it was therefore especially important to integrate a complete track-and-trace solution into the new engine block finishing line it installed in 2009. At first, this seemed like a straightforward task, but upon more careful review new challenges to the optical checking systems were identified and needed to be addressed.

To maintain the ability to identify the engine blocks from the foundry through to the final machining stage, each one is assigned a serial number. Engraved into the negative moulds, a three-dimensional identifier is created in casting based on ten different alphanumeric characters. The serial number can also be used subsequently to trace the individual gray-cast component back to the original casting process. If quality issues arise, the specific product can be analyzed accordingly. Among other benefits, this means that in the highly unusual, but not impossible case of recalls being necessary, entire product batches do not have to be classed as suspect. This offers great benefits in terms of saved time and expense.

More accurate than the human eye
The greatest challenge in detecting the serial numbers is posed by possible wearing-off due to sanding and polishing after the casting process. Sanding and polishing removes residues such as minor ore deposits, but if an operator has been a little too enthusiastic in the grinding shop, it can also turn a  number "1" into what looks to the untrained eye like a number "7”. To meet this challenge Fritz Winter opted to install a state-of-the-art vision system for quality control purposes. The interaction of the camera, the red spotlighting illumination and VisionPro software provides fast, error-free visual checking of serial numbers.

The innovative Visolution GmbH company, based in Kandel, Germany installed a small but high-precision vision system capable of checking several hundred engine blocks a day, with no maintenance requirement. The Visolution inspection station is based on a 3D system with variable threshold values. This greatly enhances the character recognition accuracy. Even if the distance and position of the engine blocks varies slightly, the vision system registers the serial numbers quickly and reliably.

After scanning and image pre-processing by the Visolution software which visually enhances the image and automatically calculates the threshold values, Cognex's SearchMax vision tool then plays a key role. It enables the intelligent vision system to handle even the finest of final variance. SearchMax is a component of the VisionPro vision software suite of library tools, which are recognized and used globally in hundreds of thousands of applications.  This add-on enhances VisionPro's capability for dealing with particularly complex demands. The tool is of special benefit for applications in which geometric data is insufficient to detect small or extremely out-of-focus patterns and coloured objects clearly and reliably.l


You can now view all QMT Magazine issues on your favourite tablet or smart phone.
Download the free Quality Manufacturing Today App from the Apple iTunes App Store or from QMT Magazine on Google Play.

Rob Tremain Photographer
Click above to see full page display and links to QMT articles.
Hexagon Logo 2
Nikon logo
Control logo