Prediction of Springback in CNC Tube Bending Process Based on Forming Parameters

CNC tube bending machines are commonly used in several industries such as automotive, aerospace and shipping. Especially in automotive industry, usage of tube formed geometries is common because they provide weight reduction without loss of strength. Obtaining desired dimensions and geometries is a necessity for design engineers to achieve high quality end-products. One of the easiest ways of having high quality tube formed end- products without the need of welding operations is using CNC tube bending techniques. The most common problems encountered during tube bending operations are thickness reduction, ovalisation, wrinkling and springback. Especially; springback which is defined as the deviation from the predefined bend angle after the bending operation performed is an undesirable condition that causes some difficulties in the assembly process. It depends on various geometrical parameters such as thickness of the tube, bend angle and effect of mandrel type used. Occurrence of springback is also dependent on forming parameters such as friction coefficient between dies and tube, internal pressure that is applied to the tube and axial loading. In the design stage, determination of springback and various parameters affecting springback behavior by experimental methods is quite cumbersome and costly. Therefore, prediction of springback by virtual methods such as finite element method (FEM) would shorten the time and reduces the cost of the pre-determination of springback.