Fast assembly error ID

Friday 4th May 2012
Some seem to have cracked it! 50 million assemblies built in each year. Error rate of < 0.5% PCBs with over 2,000 components Smallest component processing quantity: 0201. Courtesy: Lenzing.com

The custom build requirement in much high value goods manufacturing as cars or aircraft has raised the need for reliable and economic testing technology, even for one-off production runs. Accordingly Fraunhofer Institute for Factory Operation and Automation has come up with a solution which id in on show at Control, Stuttgart next week.

Below: Parts not installed properly are highlighted on the monitor screen. Credit: Fraunhofer IFF

Cars are increasingly custom-built customers wanting electric windows, heated door mirrors and steering-wheel-mounted stereo controls, another satisfied with the minimum basic equipment. Aircraft also have to cater for each airline looking for different interiors, lighting, ventilation, seating and monitors that are different.

Yet the customer's freedom dictates is the manufacturer's challenge: because individual parts and mountings have to be installed in different locations along the fuselage, automated assembly is often not economic. For many assembly steps, manufacturers rely on manual labor instead.

But if errors creep in, as a bracket mounted backwards or in the wrong place it  is expensive to correct later on. Today, employees use design drawings to determine whether the individual parts have been attached properly, or manufacturers use rigid and inflexible testing systems to check the part against comparison photos. This calls for an identical part for the template photo – and that can be difficult where one-offs are concerned.

Accordingly the Fraunhofer Institute for Factory Operation and Automation researchers IFF, Magdeburg have developed a reliable and economic testing technology even for one-off production runs.  

"The automated visual testing system generates a digital template and uses it to compare with the assembled components. It reliably identifies any errors," points out Steffen Sauer (left) , project manager for measuring and testing technology at IFF.

First, an automated camera system takes hundreds of photos of individually assembled holders, load-bearing elements and parts on the inside of the fuselage shell.  For every picture taken, the system determines the exact position of the camera relative to the fuselage shell. Simultaneously, the software generates the same shots again – this time using a "virtual" camera.

Essentially it creates "photos" using the data of the digital design model. The system compares the photos of real parts with the "virtual" images. If the system detects any deviations – if, say, a bracket is backwards – it issues a warning.

Parts that have not been installed properly are highlighted on the monitor screen. These steps are completely automatic. In addition to a 2-D check using the photos, the system can also check a completed aircraft fuselage in 3D: and uses design data to generate 3D data that it then compares with measurements on the real assembly.

"What's new about this system is that we convert specifications from the design models into images and 3-D data that the system can then compare this with the real images," explains Sauer.

The system also automatically draws up the testing plan: first, it identifies the best measuring position for every part to be tested. What is the best location from which to test the component in question? The system forwards the results to the robot. It in turn travels to the identified position, and shoots the two or three-dimensional images.

The other advantage to this approach is the system reacts quickly and flexibly giving a continuous process, from design to finished and assembled parts.

ESSENTIAL: DESIGN DATA 

Main challenges for researchers was to set up the virtual camera that uses design models to"photograph" the as yet non-existent component; to quickly and automatically locate the interesting areas from among the 

many millions of points in the 3D images; to locate in the mass of points tiny components, as brackets and holders to see whether they are properly fitted.

The testing technology application fields are diverse. It can be used wherever flexibility is required and individual parts are changed frequently. The only essential condition is design data must be available.

On show next week in Stuttgart Hall, the process will be ready for use in the summer. 

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