Fatigue-free at the Steel-Mill
Vision System Monitors Strip Steel Production
Smart Cameras cover a broad range of applications implemented in a diverse field of industries. Image processing expert Bi-Ber, e.g., has implemented a control system for the manufacturing of profiled strip steel based on a VC camera. Installed adjacent to a grinding machine, the high-capacity vision system continuously provides real-time data, thus allowing for optimal tool adjustment.
The strip steel band, which has a trapezoid profile, travels through the machine at 500 mm/min. The system monitors the top and the bottom width and the width of the band's flanks. The measurements must be displayed on the control monitor and must be made available for the tool position adjustment in real time.
An intelligent camera from Vision Components, which features a 400 MHz processor with a 3,200 MIPS computing power, executes the measurements. The camera, suitable for rugged industrial environments, is mounted vertically to realize downward vision. LED lights above and below the strip steel make the measurements detectable by the camera: the outer edge is discernable due to transmitted light from below, and the surface is made visible by reflected light. The camera is fitted with a telecentric lens, reproducing the measurements true to scale independent from the distance to the object. It transmits the readings to a connected monitor, which displays them.
Signal Analysis and Operation
The system software has been customized by Bi-Ber to suit this specific control application. If the measurements deviate from the defined tolerance, a warning signal is issued. The monitor displays the current values along with the average values of a freely selectable number of previous runs. Measurements outside of the tolerance level are displayed in red, yellow figures exceed the warning level, green figures are correct. The system is operated by means of a clearly laid-out keyboard and the monitor. Users can configure different types of strip steel via an operating menu. Target values and tolerances can be individually specified and saved. The strip steel type can be selected either via the menu or automatically via the digital inputs of the smart camera.
Solution with Staying Power
The camera is ready to operate approximately one second after voltage is applied.
It automatically starts the control program and continuously takes measurements until a different function is activated. The system executes up to five measurements per second. The readings are very stable and the measurement error is less than 10 µm.
Featuring a 400 MHz processor from Texas Instruments, the smart camera VC4038 has a 3,200 MIPS computing power. Its 1/3" sensor with a 640 x 480 pixel resolution provides a maximum frame rate of 63 fps (126 fps in binning mode). The VC4038 comes with 32 MB DRAM and 4 MB Flash EPROM for program and data storage. The flash capacity can be extended by 128 MB with an optional SD card. Standard equipment includes an SVGA video output, four digital inputs, four digital outputs, and a high-speed trigger input that enables jitter-free image recording even at high reading frequencies. The camera features both, an RS232 interface and an Ethernet interface, allowing for an easy integration into existing automation environments. The real-time operating system VCRT enables multitasking. The freely programmable, compact units are stand-alone image processing systems that can be integrated into a wide range of applications.
Strip Steel Production
Roll forming machines are employed to manufacture metal sheets of any thickness from steel slabs. The sheets can then be cut and shaped as required. EN norms define width and straightness tolerances. To suit the various possible applications, manufacturers and users may set down narrower tolerances. Further quality requirements on strip steel include breaking strength, even coating (to ensure, amongst other things, complete corrosion protection and color fastness), and resistance to environmental influences. Depending on the material and the measured data, different methods can be used. Coating thickness, for instance, is measured contact-free so as not to destroy the surface. In addition to mechanical testing and vision systems, sensors are employed to measure thermal and radiometric performance. Since all production steps are characterized by high throughput speed, the measuring results must be recorded and processed in real time. Vision solutions have the advantage of being suitable for industrial applications, fast and flexible: they enable exact measurements at some distance from the test piece.