Machining Mechanism And Technical Experiment Study On Micro Mill-Grinding

Micro components play an important role in many fields.Micro machining is the primary technology for manufacturing micro components.Because of the structure complexity and requirement for high precision of micro components,the micro machining technology is facing a greater challenge.Research on micro machining technology goes deeper.In recent years,micro cutting technology,especially micro milling,has achieved rapid development.In order to develop micro cutting technology,a lot of research has been carried out in various aspects,including improvement of micro machine tools,fabrication of novel tools,optimization of process conditions,and the use of laser,vibration and other auxiliary means.Grinding technology has also been applied to micro scale machining field.How to improve machined surface quality and precision has become the key issue in micro machining field.Micro mill-grinding is a novel compound technology that combines micro milling and micro grinding.It can accomplish micro milling and micro grinding in one working procedure.It is the functional superposition and process merging of the two.Micro mill-grinding has both the characteristics of micro milling and micro grinding,that is,high efficiency and high quality.The machining mechanism of micro mill-grinding is very different from that of micro milling and micro grinding.Based on the study of micro milling and micro grinding,exploratory research on basic problems and key techniques were conducted by geometric modeling,finite element simulation and experiments,in order to realize the compound machining technology of micro mill-grinding and understand its machining mechanism.The main contents are as following:(1)To discusse the material removal mechanism of micro mill-grinding,establish the geometric model of micro mill-grinding,and describe the process of material removal and surface generation.Based on the grinding geometry,the maximum undeformed chip thickness of single grit and the grinding thickness per tooth in micro mill-grinding were derived.According to the surface generation principle of micro mill-grinding,the theoretical model of micro mill-grinding surface roughness was established,based on the geometric model of surface roughness in traditional milling,considering the influence of machining parameters.The validity of the model was verified by experimental results.Finite element simulation was conducted to analyze the minimum chip thickness and the distribution and variation of some variables in cutting zone,such as stress,strain,temperature and so on.It is helpful to understand the influence of tool grits on the machining.(2)To explore fabrication methods for micro mill-grinding tool,compound tools for micro mill-grinding were fabricated by different methods,and graphical and experimental evaluations were made for the compound tools.Grain topography characterization of compound tool surface was presented.Grain density,spacing,and protrusion height distribution were analyzed.Experiments of grooving and side machining were performed using the compound tools.It's found that micro mill-grinding tools can significantly reduce surface roughness in sidewall machining,compared with micro milling tools.The main wear form of micro mill-grinding tool is grit shedding,and using cutting fluid can improve tool life.(3)To investigate the machined surface characteristic,and analyze the surface integrity of micro mill-grinding.Surface texture and topography of micro mill-grinding were presented.It's found micro mill-grinding can effectively restrain the burrs.Surface roughness,surface layer microstructure and surface hardness were investigated.Influences of processing parameters and processing modes on surface roughness and surface hardness were analyzed.The results provide the basis for the optimization of process conditions.(4)To investigate the force and temperature characteristics of micro mill-grinding in sidewall machining.The dynamic changes of cutting force and temperature in micro mill-grinding were investigated,the period and amplitude characteristics of the signals were analyzed by comparing with those in micro milling and micro grinding.Influences of processing parameters and processing modes on cutting force and cutting temperature were analyzed.Micro mill-grinding tools available were fabricated successfully,and the compound machining method of micro mill-grinding was realized.Theoretical and experimental researches were conducted.The results are helpful to understand the machining mechanism of micro mill-grinding,supplement the theoretical system of micro machining,and promote micro machining technology.