Tube bending machine modelling for assessing the energy savings of electric drives technology

The aim of the work is to carry out a comprehensive analysis of the energy saving opportunities offered by the introduction of electric drives in the rotary-draw tube bending technology. Although there is a clear industrial trend towards the replacement, especially for low tonnage forming machines, of the traditionally adopted hydraulic drives, there is a lack of scientific research that has studied its implications on energy consumption. For this purpose, an energy model for tube bending machines was developed. The parameters of the model were identified exploiting experimental power measurements performed on both a hybrid hydraulic-electric and a fully electric machine. The energy saving analysis was carried out through the updated energy models. For sake of generality, the analysis was extended considering various tube material-diameter combinations and different machine working conditions. The results showed that relevant energy savings can be obtained and that the improvements are affected by the machine throughput. It was also observed that the minimum achievable energy saving is significantly higher (at least three times) than the energy share for processing the tube. An efficiency analysis of both types of machines was also reported. The introduction of the electric drives allows increasing the machine efficiency up to 50 percentage points. This achievement slightly decreases with the increment of the rotary-draw bending machine throughput.