Off-line path programming for three-dimensional robotic friction stir welding based on Bézier curves

Abstract

Purpose Robotic friction stir welding (RFSW) is an innovative process which enables solid-state welding of aluminum parts using robots. A major drawback of this process is that the robot joints undergo elastic deformation during the welding, because of the high forces induced by the process. This leads to tool deviation and incorrect orientation. There is currently no computer-aided manufacturing/computer-aided design (CAD) software for generating off-line paths which integrates robot deflections, and the main purpose of this study is to propose an off-line methodology to plan a path for RFSW with the integration of the deflections. Design/methodology/approach The approach is divided into two steps. The first step consists of extracting position and orientation data from CAD models of the workpieces and adding the deflections calculated with a deflection model to generate a suitable path for performing RFSW. The second step consists of the smooth fitting of the suitable path using Bézier curves. Findings The method is experimentally validated by welding a curved workpiece using a Kuka KR500-2MT robot. A suitable tool position and orientation were calculated to perform this welding, an experimental procedure was set up, a defect-free weld was performed and a high accuracy was achieved in terms of position and orientation. Practical implications This method can help manufacturers to easily perform RFSW for three-dimensional workpieces regardless of the lateral tool deviation, loss of the right orientation and control force stability. Originality/value The originality of this method lies in compensating for robot deflections without using expensive sensors, which is the most commonly used method for compensating for robot deflection. This off-line method can lead to a reduction in programming time in comparison with teach programming method and leads to reduced investment costs in comparison with commercial off-line programming packages.

Analysis of typical working conditions and experimental research of friction stir welding robot for aerospace applications

“…In addition, due to the manufacturing and clamping errors of the thin-walled surface and the limitations of the welding equipment, trajectory planning, and programming are tedious. 20–24 As such, friction stir welding equipment are required to have not only high stiffness and precision welding performance, but also a large workspace, globally accessible trajectory gesture, and the use of good process characteristics should be easy to program.…”