Research On Path Planning Algorithm Of Directed Energy Deposition Process Based On Voxel Model

Directed energy deposition(DED)can be used to fabricate large-scale metal parts efficiently,and has wide application prospect in field of aerospace,shipbuilding,automotive and other.The other additive manufacturing technologies usually adopt unidirectional planar slicing which require support structures to ensure the successful formation of the overhanging structure.However,the support structure is unusable in directed energy deposition process,which limits the ability of DED to fabricate complex structures.Due to the high degree of freedom of the five-axis machining center,the build direction can be changed continuously during the deposition process to build parts without support structure.However,it’s a challenge to the current path planning process.Therefore,this paper proposed a directional energy deposition path planning algorithm based on voxel model.With the help of the simple structure and low accuracy of the voxel model,the complexity of path planning is reduced and multimaterial deposition is supported.To obtain accurate voxelization result,the voxelization is carried out by intersecting the triangular face with the voxel.The normal vector information of origin surface is recorded in the voxels.In order to speed up the voxelization process,fast intersection test and separation axis test are used to determine whether a triangle intersect with the voxel,avoiding the use of complex calculations such as distance calculation formulas.After the voxelization is completed,in order to find the voxel neighborhood faster,a three-dimensional array structure is used to store the voxel model.For simple parts without overhanging structures,the voxelization result can be used as the result of slicing result for path planning process.For the parts with overhanging structure,which introduced by the inclination angle.An adaptive multi-directional slicing method is proposed.When slicing a new layer,the build direction of the previous layer will be use first to determine whether the intersecting surface voxels meet the max tilt angle limit.For those layers that do not meet the condition.The new build direction can be determined by solving minimum circle coverage problem of the normal vector recorded in the contour voxel,and then slicing this layer again.For the path filling after slicing,two path planning strategies are proposed: contour scan path and internal zigzag scan path.The contour path is filled with surface pixels that has a 4-adjacent relationship with the empty pixel outside the model.The zigzag path uses a series of parallel scan lines to intersect with the contour pixels to obtain the start and end points of the deposition path,and then fill the path points between the start and end points according to the spacing.These path points record the layer thickness,material properties,and tools posture and other information.Combining the research work above,a directed energy deposition path planning software was developed,and a tire mold was deposited on a DED platform based on ABB robot,which verified the effectiveness of the algorithm.