MSW Research

 
 

MSW Publications
Some of the principal staff at Metrology Systems Wales have been engaged in Roll Measurement since the early 1970's.  The following is a selection of published papers which give an indication of how the roll measuring equipment has evolved into the present state of the art CADNO system.

 
 


"The metrology of large cylinders - exploiting the geometry ", Armstrong D.A., Thomas R.H., Chartered Mechanical Engineer, Sept 1987 pp41-4.

"The inspection of ground rolls - theory into practice ", Armstrong D.A., Thomas R.H., Murray-Shelley R., Chartered Mechanical Engineer, Nov 1987 pp44-7.

"Optimising roll life in wide strip rolling ", Steel Times International, Nov 1989 p33.Electronic roll profile measurement, Display and Analysis, Paper Technology Vol. 35 No. 10, Dec 1994 pp30-34.

"Accurate measurement and analysis of roll profiles ", Mike Walters, Steel Times, Vol.224 No. 6, June 1996, p230. High accuracy roll inspection - a new concept in roll measurement, D.A. Armstrong, Steel Times International, Vol. 13 No. 5, Nov 1989 p40.

"Accurate measurement and analysis of roll profiles ", D.A. Armstrong et al., Conference proceedings Rolls 2000, Birmingham UK, 28-29th March, 1996.

"Optimisation of Roll Profiles in the Hot Rolling of Wide Steel Strip" , Nolle, Armstrong, Ware, Biegler-König, GALESIA'97, 2-4 September 1997, Glasgow, UK, IEE Conference Publication Number 446, pp 133-138

 

 

MSW Research Projects

Optimisation of Roll Profiles in the Hot Rolling of Steel

Acknowledgement
This research is a collaborative project between The Open University, The University of Glamorgan, Fachhochschule Bielefeld, and Metrology Systems Wales.

Background
There is a world-wide over-capacity for wide steel strip. In such a buyers’ market, producers need to offer a high quality product at a competitive price in order to retain existing customers and win new ones. Producers are therefore under pressure to improve their productivity by automating as many task as possible and by optimising their process parameters to maximum efficiency and quality. One of the critical processes is the hot rolling of the steel strip.

Aim of Project
The aim of the project is to develop software to assist in the optimisation of the ingoing ground profiles of the work rolls of a hot rolling finishing mill, in order to improve the physical parameter ‘flatness’ of the strip (Figure 1). Initially the project concentrates on the hot rolling of steel, however it is hoped that the findings can be used in other rolling processes, for example cold rolling of steel or rolling of aluminium.

Figure 1 - Flat steel strip.

The flatness of the steel strip depends on a number of factors, but particularly on the profiles of the work rolls. Usually these profiles are initially specified by the mill stand producer, and are subsequently improved, usually empirically, by the rolling mill technical personnel. A system which could assist in optimising the roll profiles would clearly be of benefit.

The Rolling Operation

In a rolling mill the thickness of a steel slab is reduced by rolling between two work rolls in a mill stand (Figure 2).

Figure 2 - Principal Rolling Operation.

Figure 3 - Real Roll Stand.

As a consequence of the high forces employed, the work rolls bend during the rolling process. To compensate for the bending and thermal expansion, work rolls are usually ground to a convex or concave camber, which is sinusoidal in shape (Figure 4). Due to roll wear, the rolls need to be periodically reground after a specified duty cycle (which is normally in the order of four hours).

Because there is no suitable process model for a complete mill train, the problem is to find suitable work roll profiles - for each rolling programme - capable of producing strip-flatness to the specified tolerances.

Figure 4 - Initially ground profile with 70° - sine curve segment shape ( not to scale!)

Figure 5 - Pair of Work Rolls.

 

Figure 6 shows how the initially ground camber can ideally compensate for the effects of bending and expansion.

 

Fig 6(a) Unloaded Rolls

Fig 6(b) Loaded Rolls

IRoPOS
The "Intelligent Roll Profile Optimisation System" should be able to suggest optimum profiles for all the work rolls in a hot strip finishing mill while minimising the number of different profiles required.

Traditional optimisation methods are local in scope, i.e. they tend to find only local optimas. They depend on the existence of derivatives of the error function, this existence cannot be ensured in this real-world-problem: The error function of the technical systems "mill train" is disturbed from noise and is not smooth, i.e. a derivation may not exist for all points of function. This class of problems cannot be solved by mathematical methods. Genetic Algorithms are here an alternative. Due to a lack of access to real hot rolling mill trains for experimenting, the use of a process model would seem to be unavoidable. Due to the absence of a suitable analytical process model the transfer function of a particular finishing train should be learned by a neural network (Figure 7).

Figure 7 - The suggested system for roll profile optimisation

It seems likely, that the approach presented can be used not only for the optimisation of the initial ground work rolls in a hot strip mill, but also in a wide range of real-live combinatorial optimisation problems where experiments are impractical on the real process and no analytical knowledge of the process - and hence no process model - is available.

References
Nolle, Armstrong, Ware, Biegler-König: "Optimisation of Roll Profiles in the Hot Rolling of Wide Steel Strip", GALESIA'97, 2-4 September 1997, Glasgow, UK, IEE Conference Publication Number 446, pp 133-138

Contacts

Dr. L. Nolle
Senior Lecturer in Computing
Nottingham Trent University
email: lars.nolle@ntu.ac.uk

Dr. D. A. Armstrong
The Open University in Wales,
Faculty of Technology
Cardiff, CF1 9SA, UK
email: d.a.armstorng@open.ac.uk

Dr. J. A. Ware
The University of Glamorgan,
Division of Mathematics and Computing
Pontypridd, CF37 1DL, UK
email: j.a.ware@glam.ac.uk

Prof. Dr. F. Biegler-König
Fachhochschule Bielefeld,
Fachbereich Mathematik und Technik
33609 Bielefeld, Germany
email: biegler@fh7serv1.fh-bielefeld.de


 
 
 
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