Image Morphology-Based Path Generation for High-Speed Pocketing

Pocket milling has long been a popular means for machining pocket features in structural parts and skins in the aviation industry. Recent advanced milling technologies pose new challenges for pocket milling path which existing contour-parallel path generation schemes cannot overcome. For high-speed machining, pocket milling path is desired to be smooth and with no tool retractions during the process, while the path stepover should be kept within a prescribed range to achieve relatively constant cutting load. These geometric constraints are also vital in the application of aircraft skin mirror milling in order to guarantee a correct and consistent thickness signal reception for real-time adjustment of the process. Traditional path optimization based on local modification can only meet a few of these constraints while others are being violated. Therefore, we propose a novel contour-parallel path generation scheme that respects all these process constraints by utilizing the idea of image morphology. The two-step scheme first generates an initial path by propagating from the rectified medial curve of the pocket shape. The initial path is then treated as a binary image being iteratively deformed and projected back into the pocket region via quadratic optimization. Experimental results show that our developed scheme can generate a smooth, tool retraction free and stepover-guaranteed path for various shapes of pocket.