TPT January 2009

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101 January 2009 ›
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
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 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)
Picture 8 : The principle
of cage forming (or linear
forming) system. Pictures
courtesy of SMS Meer
(SMS Group) and its
modelling in Copra
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