Adaptive speed control for waterjet milling in pocket corners

Milling thin titanium alloy workpieces using conventional manufacturing processes is a delicate operation. During machining, the cutting forces can deform the part, while resulting compressive stresses could actually enhance its mechanical properties. Nevertheless, when parts are both large in size and thin, deformation generated by machining will be incompatible with the geometrical specifications. From this perspective, abrasive waterjet milling offers a suitable alternative solution. Numerous works present the results relating to the depths milled, the surface characteristics and machining strategies when milling pockets. Such studies show that the change of direction when milling closed pockets generates defects arising from the distribution of the jet’s energy over the milled surface or the kinematics of the machine. When a pocket corner radius is imposed, changes of direction are made following circular arcs with a radius lower than the specified one. In the present paper, an analysis of the width milled during successive circular trajectories is presented and a predictive model for the depth is adopted. This model is then used to propose a milling method that allows both the imposed radius and tolerance on the pocket depth to be respected.