Method Research And Software Development Of Surface Modeling For Non-pair Forming With Multi-press Head

In the process of ship hull construction,there are a lot of doubly curved hull plates to be formed.The present forming method used by the shipyards,which combines cold bending and lineheating,are backward and can not meet the requirement of automation and digitization of the shipbuilding production.The first ship 3D CNC bending machine both at home and abroad,which is developed by Wuhan University of Technology and Shandong Shuoli Machinery Company,uses the technology of non-pair forming with multi-press head.It's a flexible forming technology.By adjusting the height of each lower die pressheads,we can get different shapes of curved surface,which means different shapes of plates can be formed after the upper die put pressure on the plate.The first step of forming a doubly curved hull plate by ship 3D CNC bending machine is the shape adjusting of the lower press die,and the shape adjusting data is obtained by the surface modeling for ship hull plates based on non-pair forming with multi-press head.In this paper,the method of surface modeling based on non-pair forming with multi-press head is studied.The main research contents are as follows:(1)Two format files,XML and TXT are studied,which contain sheet metal surface data provided by the system of ship production design.The sheet metal surface data is exacted form the files and constructs the sheet metal surface by B Spline surface modeling technology.(2)Based on B Spline surface,the expression of three side surface is studied for three side plate,the method of intercepting a sub surface is studied for sheet section forming and the method of reversing a ppoint on the surface and calculating a point near surface approximately calculating the height of lower die pressheads are proposed.(3)According to the structural features and stamping process of ship 3D CNC bending machine,the method of surface modeling based on non-pair forming with multi-press head is proposed.Through the process of flating the surface,splitting the long plate,flating the sub surface,selecting press heads and calculating the height of selected pressheads,as well as correcting the height of pressheads,the shape adjusting data of the lower press die for each plate section is obtained.(4)The software for surface modeling based on non-pair forming with multi-press head is developed by C# language on the Visual Studio programming platform.A three-dimensional display platform is built on the basis of OpenGL,which realizes the visualization of ship hull plate and the simulation of lower press die shape adjusting of the ship 3D CNC bending machine.The software can read the sheet metal surface data file and output the shape adjusting files of lower press die and a drawing for placing the plate on the press die after the surface modeling for ship hull plates based on non-pair forming with multi-press head,which realizes a seamless data link between the hull production design software and ship 3D CNC bending machine integrated control system.(5)The regular surfaces(sail shaped surface and saddle surface)are used to test the precision of the method of surface modeling based on non-pair forming with multi-press head.The results show that the method has a high precision,which can meet the engineering requirements.What's more,the denser the surface data points are,the higher precision is.The application examples show that the method applys to different types of doubly curved hull plate,and the results of lower press die shape adjusting of ship 3D CNC bending machine are good.