Research On Trajectory Planning Of Adding Material Technology For On-site Parts Repair

When a ship goes to sea for a long time,the working environment of its large parts is relatively bad,which is prone to severe wear and fatigue failure,leading to damage.If the large parts are not repaired in time,it will affect the normal navigation of the ship.Therefore,it is necessary to develop an additional and reduced material machine tool,which can repair large damaged parts on site and make the ship recover its working ability quickly.This topic originates from the pre-research project of on-site repair of large damaged parts.The layering of STL data model,the acquisition of processing path and the interference checking of object movement in the process of adding material forming are studied.The following aspects are accomplished:Firstly,the principle of incremental manufacturing is analyzed,and it is clear that incremental manufacturing is a process of layered discretization of data model and stacking of entities layer by layer.The STL files of the added material manufacturing are processed,the information of points and facets is read and stored,the "step effect" is analyzed,and the manufacturing accuracy is measured according to the volume difference.This paper presents a P-H hierarchical algorithm,which improves the problem of single hierarchical direction of data model and obtains the optimal hierarchical direction.The STL model is stratified according to the hierarchical direction,and the boundary contour of a single slice is obtained by using the adjacent relationship of triangles.At the same time,the P-H hierarchical algorithm introduces the change rate of intersection line length and area to solve the problem of too large thickness of the slice.Layer thickness is adjusted to reduce the step effect.The layering process is simulated by using Matlab software,and the results of different layering algorithms are compared to verify the correctness of P-H layering algorithm.Secondly,according to the intersecting contour lines obtained after layering,the melt coating area of each layer of slice is determined,and the processing trajectory of the added material manufacturing is determined according to this area.Aiming at the problem of offset intersection in offset filling of contour lines,a modified offset algorithm is proposed,which solves the redundancy in filling process.At the same time,for slices with cavity holes,the reciprocating scanning filling algorithm and the sub-area scanning filling algorithm are used to obtain the processing path.In view of the above-mentioned acquisition methods of each processing path,the correctness of the method is verified by using Matlab software.Finally,aiming at the interference problems that may occur during the movement of the material adding device and the fixed object,the method of bounding box is used to check the interference quickly.By analyzing the construction of various bounding boxes and the difficulty of detection,the method of using S-O bounding box is proposed to check the interference.The type of bounding box is changed according to the distance,which improves the detection efficiency of the interference checking.At the same time,the algorithm of bounding box interference checking is validated by using the software of Matlab,and the detection process of object motion is displayed,which achieves the purpose of fast checking object interference.