Research On 5-axis CNC Incremental Forming Method Based On Point-pressing

At present,3-axis CNC equipment was adopted in most of the point-pressing incremental forming studies,or a specially designed auxiliary hammering mechanism was added to the existing numerical control system to carry out the point-pressing incremental forming.The researches on the point-pressing incremental forming adopting the 5-axis CNC equipment are less.In addition,the surface residual characteristic of the sheet part after the point-pressing forming is individual small protrusion.Aiming at this characteristic,a calculation method for the surface residual height of the point-pressing formed part was proposed in this thesis,and then a method for generating the 5-axis point-pressing incremental forming trajectory based on the calculation of the residual height was given.First,considering the surface residual height of the point-pressing incremental formed part and the efficiency of the forming process,the alternate terminal tool location point is calculated based on the latitudinal and longitudinal residual height.Secondly,the alternate terminal tool location point exceeding the maximum residual height is adjusted.If the maximum residual height is not exceeded,the alternate terminal tool location point is taken as the formal tool position,and the next alternate terminal tool location point is continuously calculated until all the terminal tool location points are obtained.The squeezing points are as sparse as possible when the maximum residual height is satisfied,which improves the forming efficiency.Thirdly,the terminal tool location points are offset by an appropriate distance along the axis of the extrusion tool as the initial tool location points.Finally,the obtained tool location points are connected in order of the initial tool location point-the terminal tool location point-the initial tool location point-the next initial tool location point as the movement path of the extrusion tool during forming.In addition,addressing the issue that sheet can not be extruded in different directions according to the surface features of the model in ordinary 3-axis numerical control incremental forming,this thesis also proposes a method for determining the spatial posture of the 5-axis extrusion tool.By adjusting the front angle and side dip angle,the sheet can be extrusion along different extrusion direction.The algorithm platform was built by VC++6.0 and OpenGL graphics library according to the proposed algorithm,which was used to generate the processing trajectory code that can be recognized by the 5-axis CNC device.A simple simulation of the forming trajectory and the spatial attitude of the 5-axis tool can be performed on the platform.The actual forming experiment also verified the feasibility of the method of generating the 5-axis point-pressing incremental forming trajectory and the method of determining the spatial attitude of the 5-axis tool proposed by this thesis.The 5-axis point-pressing and consecutive pressing incremental forming experiments were carried out under the same residual height conditions to contrast the forming effects of the sheet parts.Considering that the extrusion tool head can press the sheet in different directions in the 5-axis point-pressing incremental forming,but different point-pressing directions may have different influences on the forming quality of the sheet part.Therefore,in this thesis,by defining the point-pressing direction angle,the actual forming experiment was carried out at the point-pressing direction angles of 30°、 45°、 60°、 75°、 90° under the same condition of the terminal tool location points.The influences of the point-pressing directions on the forming quality of the sheet parts were investigated.