Design,Manufacture And Experimental Research Of CFRP Helical Milling Hole Bi-directional Machining Tool

Carbon fiber reinforced plastics(CFRP)is an advanced structural material with superior properties,which is widely used in high-end manufacturing fields such as aerospace.However,carbon fiber composite materials are typical hard-to-machine materials,and they are prone to defects such as burrs and severe tool wear during the helical milling of holes.In order to realize the high-efficiency and high-precision hole of CFRP,this paper has carried out the research on the design and manufacture of stepped bi-directional end milling cutters for CFRP helical milling holes,combined with comparative experiments,to verify the machining performance of spiral holes.Based on this,the tool wear process and wear mechanism,cutting force,and hole quality of stepped bi-directional end milling cutters milling CFRP were researched,and the following conclusions were obtained:First,according to the characteristics of helical milling hole cutting technology,a bi-directional helical milling strategy is proposed,and the structure of the bidirectional end milling cutter is designed.The geometric model of the stepped bidirectional end milling cutter and the mathematical model of the equal pitch spiral cutting line are established based on the design scheme.Secondly,according to the structural characteristics of the stepped bidirectional end milling cutter,the conversion equation of the grinding wheel coordinate system and the workpiece coordinate system was derived,and a mathematical model of the grinding trajectory of the spiral groove of the stepped bidirectional end milling cutter was established.The grinding process of the milling cutter is formulated in the cutting process,and the grinding process of the stepped bi-directional end milling cutter is simulated by NUMROTO grinding simulation software to optimize the milling process of the bi-directional end mill.A five-axisCNC grinder was used for grinding,and a ZOLLER cutter was used to check the geometric accuracy of the stepped bi-directional end mills that were shaped.Then,a comparative test of CFRP for bi-directional spiral milling with a stepped bi-directional end milling cutter and a symmetrical bi-directional end milling cutter are designed.The cutting force,tool wear,and hole quality during reverse cutting are used as evaluation indicators.Evaluation of the cutting performance of CFRP by end mills and symmetrical bi-directional end mills.It was found that compared with symmetrical bi-directional end mills,stepped bidirectional end mills have smaller axial forces during machining and reverse cutting.The wear of the blade is relatively light,and the quality of the hole is better.The wear of reverse cutting edge is relatively light,the deviation of hole diameter is relatively small,and the quality of hole making is more excellent.Finally,the tool wear morphology and process evolution,tool wear mechanism,cutting force,and hole making quality of CFRP with stepped bi-directional end milling cutters for CFRP are carried out.The results show that: during the middle and early stages of milling,the forward and reverse cutting edge regions of the milling cutter generated scoop-shaped and strip-shaped wear bands under the action of the abrasive wear mechanism;in the later stage of milling,the forward cutting edges were generated by the fatigue wear mechanism.The coating fatigue cracks,and the reverse cutting edge area is dominated by oxidative wear mechanism.As the tool wear increases,more and denser burrs appear in the entrance area of the hole than in the exit area of the hole;compared to the axial force generated by the forward cutting edge,the axial direction produced by the reverse cutting edge.The force is smaller and the growth rate is slower.The machining quality of the hole exit area has been improved obviously.