Strip thickness profile and flatness after rolling in 20-high cluster type rolling mills are simulated with a segmented model. The model is based on bending and flattening of the roll package and feedback of the residual stresses of the strip. Since the model is derived from physical principles, it has a wide working range of the input data.

The influence of roll profiles, roll shift and saddle displacement can be calculated for any rolling mill and strip geometry. The simulation program, Cluster is developed for PC and is fast enough to allow extensive simulations. Roll pass schedules can be optimised considering the available control equipment. Flatness control strategies can be developed.

Cluster is calculation software for simulations after rolling in a 20-high cluster rolling mill. This type of rolling mill is built and constructed for cold rolling of hard material to thin thickness. In this mills the placement of the rolls are important, you let the working rolls lean against a whole package of rolls, this is illustrated in figure 1.

Cluster let you freely set values for all the rolls, considering their:

• Diameter (mm)
• Young's modules (Gpa)
• Parabolic camber (mm)
• Distance between the centre of the mill and the centre of each roll. (mm)

You can also set up the profiles for the rolls, where you determining the distance from the rolls left or right side depending which roll you working with. The profile give also a variable which tell us how much the diameter of the roll has shrunk from its nominal value for its original position.

Figure 2 - Cluster setting up different variables for the rolls diameter, young's modules, parabolic camber and distances.

Demonstration example of the Simulation program, Cluster. The program includes models for simulations of elastic deformation of the roll cluster during flat rolling in 20-high mills. Powerful control parameters like, taper roll shift, asU roll positioning and roll profiles are all included in the program package. Advanced calculations are made for get a useful result of the simulation. They are:

• Strip profile
• Strip flatness
• Elastic deformations of all rolls
• Force distribution at all roll surfaces
• Reductions and stresses

In the demonstration of Cluster are almost all the models and control parameters available. The only limitations Cluster Demo have in relation to its original program are certain diameter profiles for different rolls. Also the roll body length of the rolling mill and the number of passes are not available to change.