BMW is using a high-performance imaging system employing 26 digital cameras at its factory in Landshut, Germany. The system is designed to test instrument panel carrier frames for the Mini Countryman.
Ziemann and Urban, a testing and automation specialist located in Moosinning (Bavaria), developed the self-contained test chamber for inspection of the carrier’s geometry, utilising FireWire cameras from Allied Vision Technologies (AVT).
The testing system provides 100 per cent measurement of the frame’s dimensional accuracy during production and within the production environment. The position of attachment points – such as those for airbags and steering columns – are measured in 3D. Moreover, the system monitors the presence and absence of burr on bore holes and openings for the assembly of interiors and other components. The measurement occurs within five seconds, and the installation is able to inspect two product varieties – left- and right-hand drive models.
The instrument panel carrier is positioned and clamped in a customised apparatus to avoid inaccuracies. For 3D measurements, two sets of eight AVT Guppy F-033 cameras with VGA resolution are used — one set each for the left- and right-hand drive versions. With the aid of several laser line projectors, the object’s geometry is highlighted in the image. Measurement points are illuminated with LED spotlights as well as by surface background lighting.
For presence detection of bore holes and openings, six AVT Stingray cameras with 1.25 to 5 Megapixel resolution inspect the component from top to bottom. Bore holes are highlighted by the light box integrated into the fixture, which illuminates the frame from below. Four more AVT Guppy F-036 cameras with VGA resolution inspect angular test points that are undetectable from above.
In that all cameras, laser emitters and lighting units are permanently mounted and the test object is not moved, Ziemann and Urban fulfils all of the BMW Group’s precision requirements. Even deviations caused by temperature are compensated for by special decoupling devices on the cameras as well as continuous monitoring of the temperatures of the component, the measurement device, and the environment. The result is a measurement precision of approximately 25µm, which normally is only achieved in air-conditioned inspection rooms.
‘We chose AVT cameras for a number of reasons,’ Urban explained. ‘Due to its very compact dimensions, the Guppy integrates wonderfully into an installation where 26 cameras have to be housed. Its FireWire interface is especially well suited for such a multi-camera system; with one cable, the camera can be supplied with power and controlled via software trigger, and its image data can be transmitted as well. Beyond that, we’ve been working together with Allied Vision Technologies for many years. The quality and reliability of their cameras have proven themselves.’
