Research On Milling Performance And Surface Topography In High Speed Extra-close Pitch Milling Of Nodular Cast Iron

Nodular cast iron has high strength,toughness and wear resistance,resulting in high temperature and serious wear of tools during cutting.The milling process of large size plane,such as engine box and cylinder head,not only requires high surface quality,but also requires high processing efficiency and tool life.Traditional cutting technology is difficult to meet the requirements.Extra-close pitch milling can significantly improve production efficiency while improving machining quality and better equipment efficiency.The research on the mechanism of extra-close pitch milling and the optimization of cutting parameters are of great guiding significance to the actual processing and production.In view of the imperfect characterization of the surface features of large surface milling of nodular cast iron,low machining efficiency,and unstable machining quality,this paper focuses on the study of extra-close pitch milling performance and the geometry of the milling surface,especially for high power density engine casings and cylinder heads for nodular cast iron with efficient,high-quality milling technology.The main research contents and achievements of this article are as follows:(1)The influence factors of surface roughness and the influence of cutting edge number on the milling performance of QT400-15 were studied through the path analysis and milling test.The results showed that the large diameter face milling cutter is more suitable for high speed milling and extra-close pitch milling,and the smaller surface roughness can be obtained.Increasing the number of cutting edges could lead to a significant increase in cutting force,which is limited by the rigidity of the cutting system and the power of the spindle.(2)The influence of cutting edge number on the cutting force per tooth,the deformation of the material and the mechanism of the cutting tool wear were studied by the milling test.The cutting force per tooth of extra-close pitch milling was less than that of conventional milling,but the amplitude of cutting force increased.The increase in the number of cutting edges made it possible to reduce the burrs on the edge of the chips due to the spheroidal graphite and made the cutting process more stable.The tool failure mode of milling nodular cast iron was the adhesive wear of the flank.Increasing the number of cutting edges could significantly improve tool life and milling efficiency.(3)The factors affecting the surface roughness of the face milling were modeled and analyzed.The formation of the surface geometric features of extra-close pitch milling was studied,and the fractal dimension and the surface roughness were combined to characterize it.The infiuencet of the runout error of the cutting edge on the surface roughness can not be ignored;the surface geometric features and the residual tensile stress of the different positions and directions of the milling surfaces were different,and the increase of the cutting edge number could reduce the surface roughness and residual tensile stress and increase the fractal dimension.(4)Through the orthogonal experiment of extra-close pitch milling,considering the factors of milling efficiency,machining performance and surface quality,in view of the process optimization of extra-close pitch milling of spheroidal graphite cast iron,the combination of high quality and high efficiency cutting parameters was obtained,and the regression analysis of the surface roughness value was carried out.