Integration of machining simulation within a multibody framework: application to milling

Abstract

Machining simulation has become in a few years an essential asset for industries specialized in the manufacturing of high-added value parts. Workpieces are usually milled by achinetools in order to get an accurate surface. However, machine-tools are very expensive and can operate only over a limited workspace. Therefore, some businesses shift towards robotic machining to produce their moderate-precision parts at a lower cost but all the phenomena involved in this technology aren't well understood. This paper lays the basis of a simulation environment dedicated to robotic machining by combining a milling routine (DyStaMill) and a multibody library (EasyDyn) which will be used further to simulate the behaviour of the robot. Some standard milling tests have been performed in order to validate the coupling of the milling and the multibody aspects. First, a mill moving at a fixed constant speed and machining a rectangular part is simulated to check the prediction of the cutting forces. Then, some degrees of freedom representing the vibrations of the mill along the x- and y-axes are added to the model through spring and damper systems in order to get closer to real machining conditions. Stability lobes charts are plotted and compared to previous results from the literature. A good agreement is observed among those results, demonstrating the validation of the coupling of the multibody library and the milling routine. Finally, the multibody model is applied to the case of a 3-DOF planar robot submitted to cutting forces.