J. Vizoso

Calibration of thickness measurement instruments based on twin laser sensors. Isoline bilinear look up tables

We present a procedure for the calibration of an instrument for noncontact thickness measurement of stainless steel sheets, based on a pair of triangulation laser sensors. Firstly, we carry out a general review of the architecture of this kind of instrument and of the problems associated with noncontact measurement based on commercial laser sensors in an industrial production environment. Secondly, we introduce a method for the calibration and characterization of this instrument based on the piecewise linear approximation of the isoline curves obtained in the calibration process (isoline bilinear look-up tables). We follow with a description of the searching and calculation of thickness in these types of tables.

Image processing for surface quality control in stainless steel production lines

In this paper we present an image processing algorithm to detect and measure the amount of residual oxide remaining on the surface of stainless steel coils for quality control in a production line. This algorithm processes in real time the images taken by the acquisition system which we have designed for this purpose and which has been installed in the finish line of a stainless steel production factory. We present here a more robust and reliable algorithm than the initial one, which has been adapted to deal with non-ideal conditions such as non-perfect homogeneous lighting, different surface finish, water marks, etc., which usually occur in practice.

Residual oxides detection and measurement in stainless steel production lines

In this paper, we present a system to detect and measure the amount of residual oxide stains remaining in the surface of stainless steel coils after the pickling process in a production line. The system is able to acquire clear images of the stainless steel surface with the appropriate illumination and magnification, while it is being produced. These images are processed and analyzed in real time in order to detect and measure the oxide stains which typically are between 50 and 200 microns in size. We present here an outline of the acquisition system and the image processing algorithm which has been designed to detect this sort of defect.

Filtering of impulse noise from laser sensor signals in the process of non-contact thickness measurement in a stainless steel sheet production line

The filtering of noise in data coming from measuring systems in the production environment is an area worthy of special attention. In this article we will introduce the detection and elimination of impulse noise in a series of time measurements adapting techniques of median based filters. First of all, we will describe the impulse noise phenomenon, more important when a sensor pair is considered, and analysed the problems associated with the application of these techniques in a series of time measurements. Subsequently we will develop and apply a progressive iterative method for the detection and elimination of impulse noise, that obtains more than acceptable results, overcoming problems normally associated with these types of filters.

Supervision model for the annealing process in a stainless steel production line

Annealing is an important process in the production of stainless steel coils. In this paper we present a system for supervising this process in a production line. To implement it, we need to acquire continuously the temperatures along the annealing furnace and the speed of the line and to correlate them with each production units or coils. In order to manage all that information, a simple model of the furnace has been built and simple annealing functions have also been proposed whose integration along a space-time trajectory provides a powerful supervision tool for the quality control engineer.

An Empirical Model of the Decarburization Process in Stainless Steel Production

The argon-oxygen decarburization (AOD) is the refining process of stainless steel to get its final chemical composition through several stages where tons of materials are added and oxygen and inert gas are blown. We present in this paper the design of an empirical model of this process to predict critical values of the decarburization process in order to automate it and enhance the production performance of the AOD. We show that it is possible to build an empirical model, simpler than analytical parameterized models, based on Multilinear Regression or Neural Network Perceptron to predict the amount of oxygen to be blown and the temperature to be reached.

A study of the deviations in thickness as detected by a laser measuring instrument in a stainless steel production line

Continuous, high precision, non-contact measuring of stainless steel flat rolling mill coils at the time of production is an important requirement in quality control. This paper describes the main features of the high precision laser instrument we have developed and installed on the annealing and finishing line of a stainless steel factory. Also presented are some of the results obtained from the studies, which prove the laser-based instruments can offer the robustness and precision required for use in the stainless steel and heavy industries.

An approach to the analysis of thickness deviations in stainless steel coils based on self-organising map neural networks

The aim of this work is to classify the sections of coils produced on a cool rolling mill that have an irregular thickness pattern, in order to achieve a homogeneous thickness in each coil. In order to do this investigation, we have employed a self-organising map (SOM) of neural networks, a new segmentation and clustering algorithm, filters to reduce the noise and, finally, a classification calculated from the difference between the value of each sample taken and the average of them all. We have introduced an alternative approach, with improvements in the segmentation and clustering steps, which has been successfully applied in an industrial production line. Some of our limitations and future areas for investigation are also included.