Abstract: Through a delamination mechanism analysis in the helical milling of carbon fiber reinforced polymers(CFRP)， a critical axial force model is put forward based on the classic theory of plates and shells， which is used to resolve the exit delamination state.The model analysis shows that the thickness of the uncut material is an important factor affecting the material’s exit delamination in the helical milling process， and with the decrease of the thickness， the probability of exit delamination increases. Experimental study on the helical milling of CFRP is carried out， and the results show that the maximum deviation of the critical axial force of the model is about 13.48%. The full-factor experimental results show that the axial force decreases with the rise of the spindle speed， increases with the rise of the feed per tooth， and increases with the rise of the axial cutting depth per revolution. The tool wear has a linear relationship with the axial force. Under the conditions of 0.02mm/t feed per tooth， 6000r/min spindle speed and 0.1mm/r axial cutting depth per revolution， the axial force is the minimum.

Key words: helical milling; carbon fiber reinforced polymer (CFRP); delamination; critical axial force