In a world characterised by growing environmental awareness and limited resources, efficiency in the manufacture of products is becoming increasingly important. The further development of roll forming can make a major contribution to resource efficiency, as this process is used to process approx. 8 – 10 % of the world's annual steel production [1] for a wide range of applications. To increase resource efficiency and further reduce the scrap rate for roll-formed products, this research project is developing a new type of adjustable straightener in collaboration with Tillmann Profil GmbH, which automatically and inline-capably straightens roll-formed profiles by means of partial rolling.

Motivation

A central challenge in the manufacturing of roll-formed products are geometric tolerance deviations that lead to scrap. They result from fluctuations in the strip material, inadequate adjustment processes or unwanted elongation caused by the process. Longitudinal defects such as bowing and twisting are particularly challenging, as they have so far mainly been corrected manually and iteratively based on experience.

The motivation for this research project is to improve this inefficient and resource-intensive procedure for straightening profiles. By developing an analytical model, previous research projects were able to demonstrate a direct correlation between existing longitudinal defects and the causal longitudinal strain distribution. Understanding this correlation makes it possible to implement a knowledge-based approach for the automated straightening of profiles. For this purpose, the novel partial rolling process is to be used, which directly manipulates the longitudinal strain distribution and can eliminate profile defects.

Approach

The aim of the project is to be able to straighten roll-formed profiles reliably, in-line and automatically using the innovative, knowledge-based “partial rolling” straightening process. Therefore, the profile geometry is to be measured at the outlet of the roll forming line and the longitudinal strain distribution in the profile cross-section is to be deduced from the profile's longitudinal geometry using an analytical model that has already been developed. Based on the longitudinal strain distribution determined, the roll gaps of a partial rolling stand are adjusted locally so that the additional longitudinal strain required to homogenise the longitudinal strain distribution is introduced into the profile. The homogenisation of the longitudinal strain distribution leads to a reduction of bow and twist in the profile. The procedure is shown in Figure 1.

In order to realise the concept described, the project must first develop inline-capable measurement technology for recording the profile's longitudinal geometry. With the support of the project partner Tillmann Profil GmbH, a new type of straightener is also being developed with which roll-formed profiles can be rolled out locally. The control system for the rolling stand is then developed and implemented. Profiles that have been straightened by partial rolling will be analysed afterwards with regard to their product properties such as geometry, surface quality and residual stresses. Finally, an inline-capable control of the straightener is developed and implemented in order to be able to automatically straighten roll-formed products.

Acknowledgement

The presented research project is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 537842522. Furthermore, we thank our project partner Tillmann Profil GmbH.

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