No profile - fans off!

The apt Hiller Group (apt Hiller GmbH) in Monheim, Germany, makes aluminium semifinished products for markets in Europe. The custom profile solutions are produced on the most modern systems with fully automated process technology. In run-out lengths of up to 60 metres, the profiles are transported via giant cross conveyors to a cold saw roller table. At the same time, the cross conveyors function as refrigerated tables on which the roughly 500°C profiles from the press are cooled down to 30-40°C. Ventilators which blow air from below through the conveying belts accelerate this process.

The refrigerated table is equipped with four rows of 45 fans. Each fan has a diameter of 500 mm. “All in all, that amounts to a power consumption of around 80 kW, which, depending on the process, runs through from Sunday evening to Saturday after the last shift,” says Hans-Joachim Hopf from apt Hiller. However, since the flexible production of different profiles means the refrigerated table is not always equally full, he wanted to find a solution to control the rows of fans if necessary, to find a way to switch off the fans above which no profile is currently located.

In contrast to light scanners, light section sensors do not create punctual light spots. Instead, they project a divergent light beam by means of line illumination. This allows the height profiles of objects to be determined with an inclined setting angle. In this way, the light section technology offers a large array of functions with regard to safe object detection and a large detection range at the same time. Furthermore, both the transmitter and the receiver are integrated in a single housing. The sensor determines depth and width information and enables the detection of objects on the basis of preconfiguration. To do this, 16 analysis windows and 16 inspection tasks are available which can be set by means of a PC via an ethernet interface.

In addition to the measuring variants of the Line Profile Sensors (LPS), which measure object profiles and supply 3D information, switching Line Range Sensors (LRS), as they are used at apt Hiller in Monheim, make completely new functionality possible. Comparable to a laser scanner, the devices detect the presence of objects - even in undefined object positions. With its large detection range of up to 800 millimetres, the LRS opens new application fields without complex sensor solutions, sensor combinations or additional evaluation units.

Since the line range sensors can detect the profiles independent of their position throughout the total detection range, a single sensor per fan row is enough. The profiles, however, are manufactured in differing lengths of at least 20 m and, depending on the profile type, arches can develop due to normal heat expansion, or the profiles can be inclined. This is why a second row of light section sensors is installed at a distance of 18 m from the first. This ensures that profiles are detected by at least one sensor even in the worst case. When neither sensor detects a profile, the fan row is switched off after a short time delay.

“With this energy-saving measure, we have reduced the operating time of the fans by about 25%. What that means monetarily for 80 kW of power can be easily calculated,” says Hopf, who has since put his worries about the contamination of the optics to rest and confirms that the function is reliable.