In machining of sculptured surface using ball-end mill cutter, machinability at the bottom of the ball-end mill is poor, and sometimes, workpiece of complex geometry can not be machined in 3-axis milling. In addition to that, the ball-end mill always produces the cusp on the machined surface. In order to decrease cusp heights in machining of the sculptured surface with the ball-end mill cutter, the tool path interval must be adjusted in consideration of the cusp height. This method requires long machining time and long polishing time. 5-axis milling yields smaller cusp heights at greater cutter path intervals compared to 3-axis milling. Cutting and polishing time in this machining process could be shorter than those in 3-axis machining process.
When machining the sculptured surfaces on 5-axis CNC milling machine with the end mill, the direction vector of the milling cutter is obtained by the fact that the bottom plane of the milling cutter must move along the tool path without interfering with free-form surfaces. Here, the z-map method is used for interference check. If the direction vectors are determined, NC-code can be generated through post-processing. The cusp heights is predicted from mathematical modeling of cutting traces on common plane defined along with tool path. Uniform surfaces were generated for the reduction of geometric error in polishing process.
Since the 5-axis machine center has a complex mechanism, its rigidity is not so great as the in 3-axis machine center. In order to reduce the machining error due to tool deflection in 5-axis milling, the instantaneous cutting force and the instantaneous tool deflection are predicted. And, in 5-axis machining of the sculptured surfaces with the end mill cutter, proper feedrate is suggested for the improvement of machining accuracy by using the prediciton of the instantaneous tool deflection. And, in pocketting with the ball end mill, proper feed and proper cutter axis direction are determined in 5-axis ball end milling for precision machining.
For machining experiments, free-form surfaces were machined by 5-axis milling with the end mill cutter and 3-axis milling with the ball-end mill cutter having straight tool path interval. And, surfaces were machined with curved tool path for uniform surface and with straight tool path maintaining cusp height to constant value. From test results and discussions, it was concluded that the machining of the sculptured surfaces on five-axis CNC machine was very effective machining method, and the method adjusting feedrate along tool path was useful for precision machining.
