Effects of path accuracy on additively manufactured specimens by laser material deposition using six-axis robots

Abstract

Additive manufacturing technologies such as laser material deposition (LMD) enable manufacturers to economically produce complex and individualized products. However, improved productivity and more economic use of LMD are necessary to benefit from these advantages in a wider range of applications. Through the use of industrial robots in LMD applications, large workspaces and geometric flexibility can be achieved at low cost. Possible effects of reduced path accuracies compared to conventional machines for LMD are not currently quantified. Initial studies suggest effects of path deviations on the component geometry. In this paper, an initial approach to investigate the influence of robot path deviations on the LMD component geometry is introduced. A novel approach toward correlation between path deviations of the robot and resulting surface waviness of the component is presented. The correlation is investigated on two different industrial robots with a powder-based LMD process. Tool center point (TCP) paths of the industrial robots are measured by means of a laser tracker. Robot TCP paths and resulting specimen surface topography are geometrically correlated and compared. The magnitude of the correlation is quantified by the calculation of the Pearson coefficient and a linear approximation of the correlation is made. In addition, the resulting correlation is checked by model calculations regarding the weld path formation as a function of the real tool paths with the aim of quantifying to what extent the waviness of the tool path is reflected in the waviness of the weld track.