Details

Autor(en) / Beteiligte

• Ferreira, Pedro Barbieri Figueiredo

Titel

Roll Forming - A Study on Machine Deflection by Means of Experimental Analysis and Numerical Developments

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2016

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Process control of roll forming is of paramount importance in today’s highly competitive market. This is due to the high productivity of the process (sheet speeds are traditionally in the range of 5-150 m/min), which leads to high costs due to downtime or due to part defects. Process setup and control, especially in the case of tight tolerance profiles, is key to stable and trouble-free manufacturing. In this context, the deflection of the roll stands during the forming process was investigated, both experimentally and numerically. This phenomenon happens due to the forming forces occurring when the sheet is being bent. This can lead to higher springback angles, part distortions and accelerated tool wear if not accounted for.A simulation model of the deflection of roll forming stands was developed, in order to investigate both the magnitude and the effects of the increase in roll gap due to deflection on the final profile and on the simulation data collected. Futhermore, an experimental roll forming line was designed and built, with which experiments were carried out to evaluate the machine behaviour during roll forming and subsequently validate the data from the numerical simulations of the process. Data collected from the experimental line included the forming load on the top roll and the displacement of different components during the process. An investigation was performed on the influence of the deflection modelling on the overall computational time and simulation stability. A simulation model is proposed which combines deflection calculation with position controlled fixed roll surfaces. The proposed model can, in certain cases, improve simulation stability and lower computation time while, at the same time, providing a better approximation to experimental conditions.It was concluded that simulations with deformable tooling considerably improve the prediction of the forming loads. As the calculated force remains approximately constant with different machine stiffnesses, modelling deflection in a simulation even when the machine stiffness is not accurately known can still be beneficial. A good match with experimental data was achieved and the numerical model was proven to be stable, further proving that the developed model is a step forward in roll forming simulation. The data collected were not enough for a conclusive evaluation of the effect of roll deflection in profile accuracy, but theoretical investigations and roll forming experience indicate that modelling of deflection in industrial roll forming simulations can lead to a better prediction of defects, and thus appropriate actions can be taken to correct these defects.