Warpage/Distortion in Machining 7050-T7451 Alloy Components

Workpiece distortion during machining operations causes loss of dimensional tolerance, increased scrap, and an increase in the number of corrective operations, leading to higher manufacturing costs. In an effort to minimize the distortions, significant effort is currently put into relieving the residual stress in workpieces prior to machining operations. However, it is not just the residual stress in the workpiece that affects the final part geometry; it is the machining strategy (tool path, tool geometry, cutting parameters, and workholding) in conjunction with the existing residual stress in the workpiece that results in the final part geometry. Many attempts have been made to model and compensate for residual stress during the machining process. Unfortunately, the idea of choosing machining parameters and a toolpath to compensate for the residual stress state of the part, so that when a part is released from the fixture it springs into the correct geometry has had extremely limited success, and has never been very generic. In principle, the compensation strategy could work, but knowing the stress state with sufficient accuracy is currently not and may not become economically viable, restricting its use to research laboratories and university settings. We are proposing an alternate, complementary solution to the compensation strategy described above, which will provide best practice recommendations and will allow the production of more accurate part with improved machine utilization. This technique will minimize the deformation of the workpiece resulting from these phenomena, given any initial knowledge of the residual stress condition. The long term goal is to create and develop a shop-floor friendly technology to increase part accuracy and machine utilization during the manufacture of monolithic aluminum and titanium aerospace parts. This technology would find applications in the whole range of military aircraft from JSF to C-17 to unmanned aircraft. Commercial industrial applications are also quite extensive and include passenger and cargo aircraft and automotive applications.