Vision-inspection system directs rolled-steel production
To optimize the process of cutting lengths of rolled steel, improve yield, and reduce scrap, British Steel (Scunthorpe, England) has installed Centurion camera-vision systems from Image Inspection (Epsom, England). These inspection systems are installed on large machinery that produces steel girders of various cross sections for the construction industry.
To produce the girders, a shear machine first cuts the 40-m billets at intervals of 5 or 8 m for subsequent processing in a rolling mill. To control the automated cutting process, the shear machine is outfitted with seven cameras: three on the feed side, one on the shear machine, and three on the output side that leads to the rolling mill.
Because the large machinery cannot ensure that each billet cut is sheared consistently at the same length, the rolling mill rolls each billet to a different length. To obtain minimum waste, the billets are measured and cut automatically under the control of a VAX computer from Digital Equipment Corp. (Maynard, MA). To image the billets before cutting, four cameras are positioned to view different sections of an 80-m sampling area on each billet.
In theory, a steel section 100 m long could be cut into five lengths of 20 m each. In practice, however, waste material is produced by the tapering of the ends of the steel sections; therefore, the cuts are made at shorter intervals. The amount of waste is logged by the VAX computer, and the data are used to control the cutting process, improve yield, and reduce scrap. A fifth camera positioned after the saw machine allows the cutting system to automatically remove offcuts for quality-control and loss-allocation purposes.
In addition to the hot and harsh factory environments that the cutting and inspection systems have to endure, the temperatures of the rolled sections vary from dull gray, through bright red, to white hot. Consequently, the cameras must capture images of varying contrast even when the ambient lighting changes. Using IMC2 cameras with external shutter controls, the inspection system is self-adaptive. Accordingly, vision-system calibration can be performed in ambient light, making installation and operation easier. In addition, camera area coverage can be increased to allow viewing of the mill area, even when there is no hot steel being processed.
