TPT January 2009

has been defined in the software database it can be re-used in any other design project. The finite element simulation model is created automatically by means of Copra FEA RF, taking into account the boundary conditions already defined during the design and layout process. What happens in the forming cage? Copra FEA RF allows the verification of the forming process and especially the evaluation of what happens with the material inside the cage. In the straight edge forming method, the material is normally guided at its strip edge and at the lower rolls only. The remaining portion is formed by a kind of ‘air bending’ with the target to get the tube shape formed in the most natural manner. The aim is to avoid any unnecessary forces working on the coil that may cause disruption to the process. The inner rolls are the only way to form from ‘inside’ the tube. They usually exist at a limited number of positions and determine whether the tube is leaving the forming lineal in a high- or flat oval shape.

 Picture 6 : The parametric roll design on Copra ® . It is possible to switch from the W-forming method (upper roll stand) to the standard edge bending method (lower roll stand) by changing the inner arc from 15° to 0° (see also picture 7)

Picture 8 : The principle of cage forming (or linear forming) system. Pictures courtesy of SMS Meer (SMS Group) and its modelling in Copra

 

 Picture 7 : Changing the inner arc (number 2) of station No 1 from 15° to 0° results in a different forming method (see also picture 6)

In other words, every setup tryout costs at least several tons of material and keeps the mill out of production until the final adjustment parameters of the cage rolls have been determined. In some cases the optimum is never achieved due to time restriction. Copra ® FEA RF software technology offers a total new way to determine an optimum setup of a cage mill by means of finite element analysis of the forming process. It offers the positioning of the cage tools based on the flower design or forming shape. There are easy input dialogue boxes for designing the cage tools and references for proper positioning. There is also a 3D collision check available where the user can verify if roll tooling and sheet strip match. There are some obvious advantages to perform a mill setup on the computer rather than on the mill by practical trials: • The software allows checking of existing mill setups for possibilities to improve the whole process • There is a substantial time and cost saving by offline simulation and verification. The mill does not need to be out of operation during these investigations. • There is improvement of quality and forming stability during the tube making process because FE analysis helps to understand the forming process. By using the software, it is possible to add, edit or remove any cage station (straight edge forming system) into the current tube mill roll tool layout using the built-in tool browser, where the forming lineal can be positioned between the existing forming stations. The cage beams are defined in a spreadsheet-like manner where every cage beam is treated as an independent part. Once such a forming lineal

101

www.read-tpt.com

J anuary 2009

›