Optimization of micro milling electrical discharge machining of Inconel 718 by Grey-Taguchi method

The optimization of micro milling electrical discharge machining（EDM） process parameters of Inconel 718 alloy to achieve multiple performance characteristics such as low electrode wear,high material removal rate and low working gap was investigated by the Grey-Taguchi method.The influences of peak current,pulse on-time,pulse off-time and spark gap on electrode wear（EW）,material removal rate（MRR） and working gap（WG） in the micro milling electrical discharge machining of Inconel 718 were analyzed.The experimental results show that the electrode wear decreases from 5.6×10-9 to 5.2×10-9 mm3/min,the material removal rate increases from 0.47×10-8 to 1.68×10-8 mm3/min,and the working gap decreases from 1.27 to 1.19 μm under optimal micro milling electrical discharge machining process parameters.Hence,it is clearly shown that multiple performance characteristics can be improved by using the Grey-Taguchi method.

Micro-milling of Pyramid Structured Surface for Implant Application

Surface modification,as a promising approach to improve biocompatibility of biomaterials,has captured extensive close attention among many researchers.Here,micro-milling technology was used in constructing pyramid micro-structures on the surface of Ti-6Al-4Vimplant.Cutting parameters,including spindle speed,feed rate and depth of cut,were optimized to control the generation of burrs.In addition,low melting point alloy was selected to extend the boundary of the workpiece as supporting material to prevent the generation of top burrs.The surface topographies were characterized using scanning electron microscope and laser scanning microscope.Results showed that the dimension of burrs decreased with the decrease of depth of cut,and the size of burrs decreased with the increase of feed rate.Moreover,burrs nearly not appeared on both sides of the micro-grooves machined with low melting point alloy(LMPA)coating.Pyramid micro-structure on the workpiece surface was built successfully by combining optimized cutting parameters(S=35kr/min,Vf=60mm/min,ap=5μm)and LMPA coating.

Investigation on tool wear and tool life prediction in micro-milling of Ti-6Al-4V

Short tool life and rapid tool wear in micromachining of hard-to-machine materials remain a barrier to the process being economically viable. In this study, standard procedures and conditions set by the ISO for tool life testing in milling were used to analyze the wear of tungsten carbide micro-end-milling tools through slot milling conducted on titanium alloy Ti-6 Al-4 V. Tool wear was characterized by flank wear rate,cutting-edge radius change, and tool volumetric change. The effect of machining parameters, such as cutting speed and feedrate, on tool wear was investigated with reference to surface roughness and geometric accuracy of the finished workpiece. Experimental data indicate different modes of tool wear throughout machining, where nonuniform flank wear and abrasive wear are the dominant wear modes. High cutting speed and low feedrate can reduce the tool wear rate and improve the tool life during micromachining.However, the low feedrate enhances the plowing effect on the cutting zone, resulting in reduced surface quality and leading to burr formation and premature tool failure. This study concludes with a proposal of tool rejection criteria for micro-milling of Ti-6 Al-4 V.

Design and Manufacturing of Ultra-Hard Micro-Milling Tool

Based on the study of existing typical micro-milling tools and the actual demand for micro-milling tools, the P3 design principle and design flow for ultra-hard micro-milling tool were introduced to give basic guidance for the optimization of micro-milling tools. Then, according to the P3 design flow, the manufacturing process of polycrystalline diamond(PCD) micro-milling tool was proposed, and the PCD micro-milling tool with diameter of 0.5 mm was developed. Finally, the micro-milling test on the slot was carried out to study the milling performance of PCD micromilling tool.

Micro-EDM Milling of Complex 3D Structure with Fix-Length Compensation Method

A human face with complex 3D structure is machined with a modified fix-length compensation method in this paper.The fast development of MEMS (Micro Electromechanical Systems) has strongly enhanced the application of new harder work materials.As a low cost,flexible,good repeatable machining process with negligible process forces,micro-EDM milling is well suited for freeform metallic micro structures.A major problem in micro-EDM milling of complex 3D structure is the electrode wear.A new CAM system based on the UG software platform is developed in order to get good accuracy and higher efficiency.A correction coefficient is introduced and deduced for the modified fix-length compensation method.Using this method a human face with complex 3D stricter is machined successfully by micro-EDM milling.

Development of a 2D Vibration Stage for Vibration-assisted Micro-milling

Vibration-assisted machining(VAM) has the advantages of extending tool life,reducing cutting force and improving the surface finish.Implementation of vibration assistance with high frequency and amplitude is still a challenge,especially for a micro-milling process.In this paper,a new 2D vibration stage for vibration-assisted micro-milling is developed.The kinematics of the milling process with vibration assistance is modeled,and the effects of vibration parameters on the periodic tool-workpiece separation(TWS) is analyzed.The structure of the vibration stage is designed with flexure hinges,and two piezoelectric actuators are used to drive the stage in two directions.An amplifier is integrated into the vibration stage,and the dynamics of the whole vibration system are identified and analyzed.Micro-milling experiments are conducted to determine the effects of vibration assistance on cutting force and surface quality.

Modelling of the In uence of Tool Runout on Surface Generation in Micro Milling

Micro milling is a flexible and economical method to fabricate micro components with three-dimensional geometry features over a wide range of engineering materials. But the surface roughness and micro topography always limit the performance of the machined micro components. This paper presents a surface generation simulation in micro end milling considering both axial and radial tool runout. Firstly, a surface generation model is established based on the geometry of micro milling cutter. Secondly, the influence of the runout in axial and radial directions on the surface generation are investigated and the surface roughness prediction is realized. It is found that the axial runout has a significant influence on the surface topography generation. Furthermore, the influence of axial runout on the surface micro topography was studied quantitatively, and a critical axial runout is given for variable feed per tooth to generate specific surface topography. Finally, the proposed model is validated by means of experiments and a good correlation is obtained. The proposed surface generation model o ers a basis for designing and optimizing surface parameters of functional machined surfaces.

Theoretical and Experimental Research on Error Analysis and Optimization of Tool Path in Fabricating Aspheric Compound Eyes by Precision Micro Milling

Structure design and fabricating methods of three-dimensional （3D） artificial spherical compound eyes have been researched by many scholars. Micro-nano optical manufacturing is mostly used to process 3D artificial compound eyes. However, spherical optical compound eyes are less at optical performance than the eyes of insects, and it is difficult to further improve the imaging quality of compound eyes by means of micro-nano optical manufacturing. In this research, nonhomogeneous aspheric compound eyes （ACEs） are designed and fabricated. The nonhomogeneous aspheric structure is applied to calibrate the spherical aberration. Micro milling with advantages in processing three-dimensional micro structures is adopted to manufacture ACEs. In order to obtain ACEs with high imaging quality, the tool paths are optimized by analyzing the influence factors consisting of interpolation allowable error, scallop height and tool path pattern. In the experiments, two kinds of ACEs are manufactured by micro-milling with different too path patterns and cutting parameter on the miniature precision five-axis milling machine tool. The experimental results indicate that the ACEs of high surface quality can be achieved by circularly milling small micro-lens individually with changeable cutting depth. A prototype of the aspheric compound eye （ACE） with surface roughness （Ra） below 0.12 p.m is obtained with good imaging performance. This research ameliorates the imaging quality of 3D artificial compound eyes, and the proposed method of micro-milling can improve surface processing quality of compound eyes.

Method of Precise Auto Tool Setting for Micro Milling

Based on microscope and image processing, a new method of auto tool setting for micro milling was presented. Firstly, a realtime image of tool setting area was obtained by microscope and CCD camera, then image processing was carried out on this image and the gap between the tool and workpiece was calculated. The gap measurement was sent to motion controlling card to make the tool approach to the surface of workpiece. These steps were repeated until the gap is zero, which means that tool setting was finished. Moreover, a reliability verification test was conducted. Results indicated that the precision of tool setting is satisfactory.

Development of micro milling force model and cutting parameter optimization

Taking the minimum chip thickness effect,cutter deflection,and spindle run-out into account,a micro milling force model and a method to determine the optimal micro milling parameters were developed.The micro milling force model was derived as a function of the cutting coefficients and the instantaneous projected cutting area that was determined based on the machining parameters and the rotation trajectory of the cutter edges.When an allowable micro cutter deflection is defined,the maximum allowable cutting force can be determined.The optimal machining parameters can then be computed based on the cutting force model for better machining efficiency and accuracy.To verify the proposed cutting force model and the method to determine the optimal cutting parameters,micro-milling experiments were conducted,and the results show the feasibility and effectiveness of the model and method.

Ti-22Al-25Nb微铣削加工参数仿真与试验

为得到合理的Ti-22Al-25Nb微铣削加工参数,用Abaqus建立Ti-22Al-25Nb三维微铣削有限元模型,设计正交仿真方案,研究铣削深度、主轴转速和每齿进给量对微铣削力的影响规律,并进行微铣削试验对仿真结果进行验证。结果表明,铣削深度对微铣削力的影响最大,每齿进给量的影响最小,得出最优的加工参数,使用该参数进行微铣削加工试验,微铣削力仿真值与试验值的平均相对误差为11.4%,验证了微铣削加工三维有限元仿真的准确性,为Ti-22Al-25Nb微铣削加工提供了参考。

Study on Surface Roughness in Micro Milling of Single Crystal Materials

Micro milling is a machining method of high precision and efficiency for micro components and features.In order to study the surface quality of single crystal materials in micro milling,the two-edged cemented carbide tool milling cutter with 0.4 mm diameter was used,and the orthogonal experiment was completed on the micro-milling of single crystal aluminum material.Through the analysis of statistical results,the primary and secondary factor which impacting on surface quality were found as follows:spindle speed,feed rate,milling depth.The ideal combination of optimized process parameters were obtained,when the spindle speed was 36000 r/min,the milling depth was 10μm,the feed rate was 80μm/s,which made the milling surface roughness is 0.782μm and minimal.Single crystal materials removal mechanism were revealed,and the influence of cutting parameters on micro-milling surface were discussed,the reason of tool wear was analyzed.Those provide a certain theoretical and experimental basis for micro milling of single crystal materials.

Research on Positioning Error Compensation for Micro Milling Machine Tool

Micro milling has many advantages in fabricating three-dimensional(3D) structure in micrometer scale. The micro milling machine tool with high positioning accuracy is of great importance for getting micro structure with high profile precision and good surface quality. Meanwhile, the method of position error compensation is a good way to improve the accuracy of the micro milling machine tools. In this paper,a software method is adopted to compensate the positioning error and improve the positioning accuracy. According to error cancellation theory,the compensation values are generated and compensation tables are built to adjust the positioning error in the NC system based on Industrial Motion and Automation Control( IMAC). The positioning accuracy of linear motor is ± 0. 3 μm without backlash after compensation. In order to verify the effectiveness of compensation on the machining performance,concave spherical surfaces are processed on the micro milling machine tool. The experimental results show that the profile radius error of the spherical surface machined with compensation decreases more than 60%.

Heat Resistant Properties of Some Elements-Incorporated Diamond-Like Carbon Films and Their Trial Applications for Micro End Mill Coatings

In this article, the results obtained from a study carried out on the some elements-incorporated diamond-like carbon (DLC) films are reported. All the films were deposited using plasma-based ion implantation (PBII) technique. The deposited films were annealed at 400℃, 650℃ and 900℃ in an air atmosphere for 1 hour. The effects of adding hydrogen, silicon/oxygen and silicon/nitrogen into the DLC film on chemical composition, friction coefficient and corrosion resistance were investigated. The films coated micro end mills performance was also assessed. The results indicate that all the films showed almost constant atomic contents of C, Si, O and N until annealing at 400℃. However, the films were completely destroyed at 650℃ with the increased Si and O contents, while the C content decreased. The incorporation of silicon/oxygen and silicon/nitrogen into the DLC exhibited lower values of friction coefficients than the hydrogenated DLC (DLC and H-DLC) before and after annealing at 400℃, whereas all the films presented the same values of friction coefficients after annealing at 650℃ due to the completely destroy of the films. Furthermore, the incorporation of silicon/nitrogen into the DLC also exhibited better corrosion resistance and unbroken micro end mills performance on their surfaces. Thus, the incorporation of silicon/nitrogen into the DLC film can be considered beneficial in improving the micro end mills performance.

Ti-22Al-25Nb微铣削表面粗糙度试验研究

为研究Ti-22Al-25Nb微铣削的表面质量并确定合适的加工参数,对Ti-22Al-25Nb进行三因素五水平的微铣削正交试验和极差、方差分析,根据振动信号绘制稳定性极限图,研究铣削深度、每齿进给量和主轴转速对加工稳定性和表面粗糙度的影响规律。结果表明,铣削深度对表面粗糙度的影响最大,主轴转速次之,每齿进给量最小,并得出最优加工参数组合,此时表面粗糙度为0.21μm。该研究为Ti-22Al-25Nb微铣削加工提供了理论支持。

5-羟色胺转运蛋白显像剂^(11)C-DASB的自动化合成及Micro PET/CT显像

目的:自动化合成5-羟色胺转运蛋白显像剂11 C-DASB并进行大鼠Micro PET/CT显像;方法:通过改变甲基化试剂、溶解前体溶剂及反应条件,得到优化的标记条件作为碳-11多功能合成模块的输入参数,进行自动化合成11 C-DASB,大鼠静脉注射11 C-DASB 45 min后进行显像;结果:采用11 C-CH3-Triflate作为甲基化试剂,通入新配制的含1mg去甲基DASB前体的500μL DMSO溶液内,80℃下加热2min,标准率为63.7%,大鼠显像表明,11 C-DASB特异性的浓聚于SERT富集区域;结论:经优化,11 C-DASB自动化合成可得到较高产率,大鼠显像表明,其特异性浓聚于SERT富集区域,有望作为5-羟色胺转运蛋白显像剂。

^(18)F-氟赤硝基咪唑micro PET/CT评价裸鼠乳腺癌早期放疗疗效实验研究

目的探讨^(18)F-氟赤硝基咪唑micro PET/CT评价裸鼠MDA-MB231乳腺癌早期放疗疗效的价值。方法建立16只裸鼠MDA-MB231乳腺癌模型,将其按照随机对照原则分为两组:对照组(A组)、放疗组(B组),每组8只。每组裸鼠行micro PET/CT显像,测定每只裸鼠肿瘤SUVmax值。完成显像后,常规HE染色观察每组肿瘤组织形态学特征,免疫组化方法测定每组肿瘤细胞乏氧诱导因子-1α(HIF-1α)的表达情况。结果放疗前,对照组与放疗组SUVmax值差异无统计学意义(t=0. 375,P> 0. 05)。放疗组放疗后48 h裸鼠肿瘤组织SUVmax值较放疗前(t=9. 958,P <0. 05)、放疗后24 h(t=16. 506,P <0. 05)明显降低,差异有统计学意义(F=58. 860,P <0. 05)。放疗后24 h SUVmax值也低于放疗前24 h(t=5. 405,P <0. 05),差异有统计学意义。HE染色结果显示放疗组肿瘤细胞坏死较对照组更加明显。免疫组化结果显示放疗组放疗后HIF-1α表达阳性率明显低于放疗前(t=14. 802,P <0. 05),差异具有统计学意义。相关性分析结果显示肿瘤SUVmax与HIF-1α的表达呈明显正相关性(r=0. 865,P <0. 05)。结论^(18)F-氟赤硝基咪唑micro PET/CT可以监测肿瘤内部的乏氧状态,并且可以评价裸鼠MDA-MB231乳腺癌的早期放疗疗效。

Influence of Microstructures on Thermal Shock and Sintering Behavior of YSZ-based Thermal Barrier Coatings

In this study, two thermal barrier coatings based on YSZ were produced by using a commercially available agglomerated and sintered powder and a special spray powder prepared by high energy ball milling. Both thermal barrier coatings exhibited similar overall porosities, but significantly different microstructures. Application of the special spray powder prepared by high energy ball milling led to a microstructure with numerous inclusions of semi-molten agglomerates, which introduced a plethora of clusters of fine pores into the coating and several more microstructural defects. This microstructure resulted in a significantly better thermal shock behavior compared to the conventional thermal barrier coating. The heat treatment of both thermal barrier coatings atθ=1150℃for t=100 h led to a sintering of both coatings. The results were reduced overall porosity and significantly increased fracture toughness. A correlation between the fracture toughness of both coatings after the heat treatment and the thermal shock life time could not be identified.

Effect of Surface Roughness in Micro-nano Scale on Slotted Waveguide Arrays in Ku-band

Modeling of the roughness in micro-nano scale and its influence have not been fully investigated, however the roughness will cause amplitude and phase errors of the radiating slot, and decrease the precision and efficiency of the SWA in Ku-band. Firstly, the roughness is simulated using the electromechanical coupled（EC） model. The relationship between roughness and the antenna＇s radiation properties is obtained. For verification, an antenna proto- type is manufactured and tested, and the simulation method is introduced. According to the prototype, a contrasting experiment dealing with the flatness of the radiating plane is conducted to test the simulation method. The advantage of the EC model is validated by comparisons of the EC model and two classical roughness models （sine wave and fractal function）, which shows that the EC model gives a more accurate description model for roughness, the maxi- mum error is 13%. The existence of roughness strongly broadens the beamwidth and raises the side-lobe level of SWA, which is 1.2 times greater than the ideal antenna. In addition, effect of the EC model＇s evaluation indices is investigated, the most affected scale of the roughness is found, which is 1/10 of the working wavelength. The proposed research provides the instruction for antenna designing and manufacturing.