Optimization of Machining Parameters for Improving Accuracy of Dimension and Shape of Bent Part in Rotary Draw Bending

This study dealt with the rotary draw bending method most used for tube bending and investigates how applied bending such as normal bending, using mandrels or pressing with booster have an effect on machining accuracy, focusing on dimensional defects due to springback and flat deformation to the transverse plane. The study used particle swarm optimization (PSO) algorithms to investigate the optimal machining conditions for improving the accuracy of dimension and shape of a bent part. The following findings were obtained: The springback during applied machining using a mandrel, or using a mandrel and booster together, is almost the same as during normal processing; The flattening near the center of the bend in applied processing using a mandrel, or a mandrel and booster together, decreases more than with normal processing at mandrel protrusion L ≥ 4 mm, and the maximum can be suppressed to approximately 0.15%; When the sum of the springback and the flattening is taken as the objective function and the minimum value is obtained, the optimal solution is around L = 7 mm.

Endotracheal Tubes Design: The Role of Tube Bending

Endotracheal tubes (ETT) passed inside the human trachea witness tube bending at different angles, affecting the ocal fluid flow dynamics. This induces a variable mechanical ventilation performance across patients’ comfortability evels. Our understanding of the ocal fluid flow dynamics phenomena is thus crucial to enhance the maneuverability of ETT under operation. For the first time to our knowledge, we shed ight on ETT through computational fluid dynamics (CFD) to investigate the bending effect of ETT on the ocal airflow in volume-controlled mechanical ventilation. We considered an ETT with 180° arc bend configuration, including Murphy’s eye. We identified several flow phenomena associated with the bending, such as flow asymmetries, secondary flows, and vortex dynamics throughout the tube.

Experimental Investigation of the Effects of Irradiating Schemes in Laser Tube Bending Process

The laser tube bending process (LTBP) process is a thermal non-contact process for bending tubes with less springback and less thinning of the tube. In this paper, the laser tube bending process will be studied experimentally. The length of irradiation and irradiation scheme are two main affecting process parameters in the LTBP process. For this purpose, different samples according to two main irradiation schemes (Circular irradiating scheme (CIS) and axial irradiating scheme (AIS)) and different lengths of laser beam irradiation (from 4.7 to 28.2 mm) are fabricated. The main bending angle of laser-bent tube, lateral bending angle, ovality, and thickness variations is measured experimentally, and the effects of the irradiating scheme and the length of irradiation are investigated. An 18 mm diameter, 1 mm thick mild steel tube was bent with 1100 Watts laser beam. The results show that for both irradiating schemes, by increasing the irradiating length of the main and lateral bending angle, the ovality and thickness variation ratio of the bent tube are increased. In addition, for a similar irradiating length, the main bending angle with AIS is considerably higher than CIS. The lateral bending angle by AIS is much less than the lateral bending angle with CIS. The results demonstrate that the ovality percentage and the thickness variation ratio for the laser-bent tube obtained by CIS are much more than the values associated with by AIS laser-bent tube.

INFLUENCE OF THE PRESSURE DIE GEOMETRY ON THE BENT TUBE OVALITY

The paper deal with analysis and optimization of the pressure bar geometry in the case of the tube bending. The bending process is realized on Wafios RBV 60 ST CNC bending machine using rotary draw bending system. The processed semi-finished product is a tube, which is made of 24MnB5 steel. Currently, after tube bending by an angle of 120°, an unacceptable ovality occurs on its body. Therefore, the article presents the optimization of the pressure bar geometry, which helps to prevent the occurrence of the mentioned defect. Due to the least possible intervention in the bending process, only the change in the pressure bar geometry is tested. For this reason, a numerical simulation in ANSYS software is performed. Before the actual optimization, an accuracy of the simulation is verified by comparing the real initial state with simulation results.

Wall thinning behaviors of high strength 0Cr21Ni6Mn9N tube in numerical control bending considering variation of elastic modulus

Wall thinning, as one of the key defects in tube bending determined the forming quality and limit, is more easily to occur due to the specific properties of high strength 0Cr21Ni6Mn9N stainless steel tube (0Cr21Ni6Mn9N-HS tube). To achieve tube accuracy numerical control (NC) bending forming, the wall thinning characteristics of the 0Cr21Ni6Mn9N-HS tube should be clarified. An analytical model was proposed to reveal the essential relation between tube parameters and wall thickness distribution. Considering the varied elastic modulus, a finite element (FE) model was applied to explore the wall thinning under different geometrical and process parameters. Using the modified multi-parameter sensitivity analysis method combined with FE simulation, the sensitivity of the wall thinning to geometrical and process parameters was carried out. The experiments of NC tube bending were conducted to validate the analytical and simulate results. The results show that the varied elastic modulus can enhance the wall thinning degree, but has no obvious effect on wall thinning characteristics. The wall thinning characteristics under different geometrical and process parameters are revealed and the reasonable parameters ranges for the 0Cr21Ni6Mn9N-HS tube in NC bending are obtained. The most sensitive parameter on wall thinning is the relative bending radius, while the bending angle is the least one.