TPT January 2009

The catalogue contains all standard types of roll tooling – from forming stations down to the calibration passes. The user can also modify each station according to specific requirements and even include auxiliary tools like drawing dies or additional ‘forming shoes’. The proper forming strategy is defined by the design of the ‘flower sequence’. This is nothing other than the actual knowhow of tube making. At this stage all the angles, radii, length compensations, dependencies, and additions for welding, calibration, and strip guiding have to be defined. In addition, certain company specific strategies or rules like ovalities have to be taken into account and defined at this stage. In the Copra software respective values are either calculated or taken from a number of tables. The user defines both methods so every company can develop specific strategies and store knowledge in the database for future use. The definition of the tube welding line (machine) and respective roll tooling method operate in the same way. Descriptive parameters such as diameters, dependencies, relieve angles, and gaps, are taken either from company specific tables or are calculated by integrated formulas (picture 5).

 Picture 5 : Machine- and roll tool definition based on company specific standards or from built-in formulas

chosen forming strategy. The decision whether to make use of the single arc forming method or a double radius forming strategy can be undertaken by a single mouse click. The user can also compare the influence of different forming methods in the break down stations like standard edge bending versus W-forming – just by the press of a button (see pictures 6 and 7). What is a cage forming system? A comparatively new feature of Copra is the possibility to design and model any type of rolling cage – often referred to as the straight edge forming method. A cage forming system is a continuous forming process by groups (beams) of single simple rolls and additional supporting outer and inner roll tools. This linear forming method can virtually be compared with ‘forming a tube by pulling a sheet of paper through a funnel’, based on a scenario where there is no entry and exit. Of course, steel does not behave like paper. It is necessary to enter a somewhat pre-formed tube into the ‘cage’ and retrieve the round but so far non-welded tube segment from the cage and enter it into fin passes and welding stations. As a cage forming system is no ‘funnel’, the number, size and position of all the forming and supporting rolls have to be optimized as well. Copra allows for a modeling of various types of straight edge forming systems due to its parametric structure. The lineal beams are either predefined or – if there are single mounted rolls – each roll and respective position is defined in specific data base tables. In order to achieve a proper forming result it is important to have a smooth strip entry into the forming cage. Therefore it is important to optimize both entry passes and the position of forming- and guiding rolls in the forming line. Such tasks have to be undertaken by ‘trial and error’ and are usually quite time consuming and pretty costly. A straight edge forming cage for a large diameter mill can easily reach a length of 12m or more – holding 4.5 to 10 tons of material. A new way to determine the correct setup parameters for a cage mill

Simple investigation of various forming strategies

Both flower and rolls can be easily adapted by the parametric system of the Copra tube mill design software. The user simply changes either the values of respective forming angles or even the

 Picture 3 : Selection of fine- or welding station during the definition of tube mill stations (Copra tube mill software module)

 Picture 4 : Definition of the so-called ‘flower pattern’

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J anuary 2009

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