【正文】 offline tool path generation approaches is that the real machining kinematics is not directly incorporated. To ensure machining precision, cutter orientation generation should be based not only on the geometry of the machined surfaces but also on the machine typespecific kinematics. In this paper, a novel methodology for solving the nonlinearity error problem in fiveaxis machining is presented. The method optimizes the CLDATA based on machinespecific kinematics and machining motion trajectory, whereby the cutter orientations are modified to reduce the nonlinearity errors provided that there is no interference between the cutter and the workpiece. A software program for implementing the proposed method is presented. As an application of proposed method, a case study is presented, which shows an increase in machining precision as pared with those processed by the existing AIGP’s method.PROPOSED TOOL PATH GENERATION METHODThe machining nonlinearity errors depend upon the actual CC point trajectory, since a CC point trajectory is a function of the machine rotary variables, each actual CC point trajectory can be manipulated within the tolerance limit by changing the machine rotary variables, provided that there is no interference between the workpiece and the cutter. Further more, because of the machine rotary variables are kinematically related to the cutter orientation changes, the nonlinearity error problem can be approached by manipulating cutter orientations. To proposed method reduces the nonlinearity errors by determining the acceptable machine rotary variables employing the machine motion trajectory model, and by modifying the cutter orientation through the machine kinematic relations. It must be emphasized that the machine kinematic properties and motion trajectory are machine typespecific. Hence, the modification of CLDATA has to be carried out in teams of machine variables and subsequent use of the kinematic transformation to determine the modified CLDATA.The procedure of the proposed method starts with the transformation of the CLDATA to machining NCcodes by employing the machinetype specific inverse kinematic model. In teams of machine variables, the actual machining motion trajectory is determined by using the specific machine motion trajectory model. Then, the machining errors are determined. The linearity error is a function of surface local curvature on the cutting curve and the stepforward distance. From the cubic spline cutting curve function, the surface local curvature can be determined. The linearity error for each move then can be puted from the adjacent CC point data and the surface local curvature. By knowing the linearity error, the allowable nonlinearity error can be determined as the difference of the linearity error from the specified machining tolerance. Using the machine trajectory model and the line segment equation, the maximum deviation can be determined. By taking sample points on both of the CC nonlinear curve and the line segments, the maximum chord deviation is the maximum nonlinearity error. In the steps where the maximum nonlinearity error exceeds the allowable nonlinearity error, the proposed method modifies the machine rotary variable changes. The modification is carried out by increasing/decreasing a machine rotary variable variation a small angle in the plane containing the two original cutter vectors, and by adding/subtracting the angle to the original machine rotary variables. The new rotary variables are then used to calculate the resultant nonlinearity error, which in turn is pared again with the allowable nonlinearity error. Thus, by using the difference between the allowable nonlinearity error and modified nonlinearity error as the criterion, the acceptable machine rotary variables can be determined iteratively. Finally, from the modified machine rotary variables, the corresponding cutter orientations can be determined by performing the forward kinematic transformation. In order to avoid interference between the workpiece and the cutter, the rotary angles were adjusted such that the angle changes are less than half of the orientation angle changes are less than one half of the original cutter orientation changes. Comparing to the existing “l(fā)inearization processes ”, the additional data points are inserted with cutter orientations either varying linearly or as the average variation(., the one half)of the rotary angle change, and the interference problem is not considered. Alternatively, the modified machine rotary variables angle change from the proposed method are smaller than one half of angel change, which thus ensures the corresponding cutter orientation are within the range such that no interference occurs. For a set of CLDATA, the modification procedure can be performed by using the following algorithm.TOOL PATH MODIFICATION ALGORITHM1. Transform the initial CLDATA, into its corresponding machining NCcodes by using the specific machine inverse kinematic model。3. Compute the desire tool path by using cubic spline function based on the CLDATA and calculate the local surface curvatures Kf of the tool path at the machining points。 Δsthe segment length between consecutive CC points from step(2).5. Compute the allowable value of the nonlinearity error: δa,n=toleranceδt.6. Determined the points on the straight line segment and on the machine motion trajectory segment that correspond to the maximum chordal deviation.7. Compute the maximum nonlinearity error , δmax, using the points from step(6)。9. Computer the machining NCcodes of Bm,i+1 and Cm,i+1 based on the machine rotary angle variation from step 8:Bm,i+1= Bm,i177。ΔCmWhere, Bm,i, Cm,i are the ith rotary variables , Bm,i+1 Cm,i+1 are the i+1th rotary variables andΔBm ΔCm are modified rotary angle changes. The +and –sign depends on whether the angles in step i+1 increase or decrease,10. Determine the optimum cutter orientations by