A method of generate intermediate process models for casing parts based on virtual control surface constraints

In numerical control (NC) machining of a multi-island casing part, establishing accurate machining process model is a key technology to realize intelligent processing of such parts. In order to obtain accurate machining process model of a multi-island casing parts, a method based on virtual control surface constraints to structure process models of a casing part is proposed. Firstly, the introduction of virtual control surface constraints in modeling process is analyzed according to machining characteristics of the multi-island casing parts, and the Lagrange transfinite interpolation modeling theory is given by combining the idea of virtual control surface constraints. Then according to geometrical characteristics of the casing parts, the algorithm for calculating the distribution position and geometric shape of the virtual control surfaces is determined; on this basis, according to the modeling theory of virtual control surface to structure the middle surface, the process model according to cutting depth constraint and plan the tool path for it is determined. Finally, a validation is conducted on a multi-island casing part. The result shows that the proposed method is able to control the geometry of process model effectively according to the distribution of machining characteristics, avoid the geometry of process surface prematurely tending to be complicated caused by handling multiple processing characteristics simultaneously and provide some effective process models for multi-island casing parts in NC machining; to some extent, the difficulty of the process planning for a multi-island casing parts is reduced.