Automatic control roller and gag press straightening operations for sections

This report contains the joint contributions of the collaborative ECSC project between Corus UK Limited (co-ordinator), Betriebsforschunginstitut (BFI) and Bohler Edelstahl GmbH. The aim of this project was to investigate methods for automatic control of gag-press and roller straightening operations. The investigation into gag-presses was undertaken by BFI and Bohler Edelstahl in Germany and Austria. The investigation into roller straightening was undertaken by Corus at Teesside Beam Mill. In both cases, straightness data was required, and this was provided by Laser Straightness Meters that view the finished product and determine a straightness value. The system has been developed and extended under this project with extensive software programming to enable the system to be used in production at Teesside Beam Mill. The system logs straightness data to a database for future use. A control program has been written which builds on a basic 1 s t order approximation to the straightening process. Extensive use of the 1 s t order model has shown that straightness is very sensitive to the setting of the last roll on the Roller Straightening Machine (RSM). It has also identified a number of straightening regimes resulting from different combinations of straightening parameters. During use of this model, it was found that it would be extremely difficult to provide a low stress product with the current set up of the RSM. In general terms, a 7 roll RSM can get a product straight, but more rolls are required to achieve a straight product with a low residual stress. A prediction algorithm has been added to the first order model to guide the user as to which roll to alter the penetration of and in which direction. This forms part of the feedback loop, with the LSM as the input, the first order model as the calculation and the output of this model the recommendation. It is possible to automate the pressing procedure in a gag press. This was shown for two different gag presses and for various sections. The information about the deviation from straightness is necessary. If it is possible to produce sections with a defined curvature, e.g. a 'homogeneous bow', the press strategy and the computer algorithm can be simplified. Mostly it will be necessary to check the curvature by a straightness measurement. Section geometry, machine parameters, material properties and more importantly customer requirements are additional values to be taken into account. Especially the mechanical equipment has to work very precisely, otherwise additional monitoring in the gag press has to be installed.