Deformation Characteristics in a Stretch-Based Dimensional Correction Method for Open, Thin-Walled Extrusions

Abstract

Dimensional accuracy of incoming components is crucial for automated welding and assembly in mass volume production. However, thin-walled extrusions made to industrial standards show severe dimensional variations, including gap opening, sidewall inclination, local convexity, and so on. Thus, one major challenge is to provide a low-cost correction method to improve the dimensional accuracy at a level demanded by automated assembly and/or product fit-up. A novel correction method called transverse stretch and local bending (TSLB) has recently been developed, enabling one to efficiently correct the dimensional deviations in thin-walled, U-channel profiles at a low cost. However, the lack of in-depth understanding of the underlying mechanism makes it challenging to efficiently optimise and control the process. In this study, the feasibility of this new technique was experimentally validated by four groups of TSLB tests with different profile dimensions, showing a dimensional accuracy improvement of about 92% compared with the as-received parts. The evolution of the critical dimensional characteristics, including gap opening and bottom convexity, is analysed numerically throughout four stages consisting of inserting, releasing, calibration, and springback. It is found that the inserting stage greatly reduces the dimensional deviations in a pure bending state, while the calibration stages further minimise the deviations in the bending and transverse stretching combined state. In addition, the wedge angle of the tool is found to be critical to the dimensional accuracy improvement. The low wedge angle facilitates the correction of sidewall inclination and gap opening, while the high wedge angle contributes to mitigating bottom convexity. The overall outcome of this study enhances the fundamental understanding of the effects of in-process stretching and local-bending on the dimensional capabilities of U-channel extrusions. This can ultimately generate guidelines that will lead to new application areas of aluminium extrusions in highly competitive marketplaces.

Lightweight Materials in Electric Vehicles

“…This technique integrates the stretching and bending mechanisms, mitigating and offsetting the springback. The dimensional deviation is as low as 0.4% of the nominal value in the case of correcting a U channel with an uneven thickness [48]. Hence, this technique can be potentially applied to future high-precision aluminium sheet parts used on EVs.…”

Single neuron PID based method for deformation suppression during CNC machining of parts

“…e is the input of the controller, that is, the difference between the measurement result and the given value, also known as the deviation. The controller is discretised and the resulting incremental digital PID control algorithm is given in Equation (2).…”

“…CNC machining is a process method for implementing part machining on CNC machine tools, which uses digital information to control tool displacement and parts, enabling automated machining of variable and complex shaped parts, and has been widely and successfully used in the machinery manufacturing industry. 2 However, in the current CNC machining process, the machining deformation of parts, especially thin-walled parts, is still serious due to the imperfection of the control platform and machining technology. Du et al proposed a multivariate chaotic time series-based prediction method for the motion accuracy of CNC machine tools in order to cope with the information loss caused by unit accuracy time series, so as to achieve the accuracy prediction of motion, and the results showed that the method prediction effect is better and has strong adaptability and practicality.…”

“…And with the development of modern technology, CNC machining has gradually become an efficient and high‐quality part processing technology. CNC machining is a process method for implementing part machining on CNC machine tools, which uses digital information to control tool displacement and parts, enabling automated machining of variable and complex shaped parts, and has been widely and successfully used in the machinery manufacturing industry 2 . However, in the current CNC machining process, the machining deformation of parts, especially thin‐walled parts, is still serious due to the imperfection of the control platform and machining technology.…”

Numerical Analyses of Deformation Mechanisms in a Novel Dimensional Calibration Technique for Thin-Walled, Open Extrusions

“…The feasibility of this technique was assessed experimentally with complex U-shape extrusions [15]. The deformation mechanisms of stretching and bending were studied by finite element analysis (FEA) [6]. Also, the die geometry was investigated and optimized, which shows a significant influence on the stress-strain evolutions and the improvement of dimension accuracy.…”