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.

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.

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.

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.

Optimal tool design in micro-milling of difficult-to-machine materials

The limitations of significant tool wear and tool breakage of commercially available fluted micro-end mill tools often lead to ineffective and inefficient manufacturing,while surface quality and geometric dimensions remain unacceptably poor.This is especially true for machining of difficult-to-machine(DTM)materials,such as super alloys and ceramics.Such conventional fluted micro-tool designs are generally down scaled from the macro-milling tool designs.However,simply scaling such designs from the macro to micro domain leads to inherent design flaws,such as poor tool rigidity,poor tool strength and weak cutting edges,ultimately ending in tool failure.Therefore,in this article a design process is first established to determine optimal micro-end mill tool designs for machining some typical DTM materials commonly used in manufacturing orthopaedic implants and micro-feature moulds.The design process focuses on achieving robust stiffness and mechanical strength to reduce tool wear,avoid tool chipping and tool breakage in order to efficiently machine very hard materials.Then,static stress and deflection finite element analysis(FEA)is carried out to identify stiffness and rigidity of the tool design in relation to the maximum deformations,as well as the Von Mises stress distribution at the cutting edge of the designed tools.Following analysis and further optimisation of the FEA results,a verified optimum tool design is established for micro-milling DTM materials.An experimental study is then carried out to compare the optimum tool design to commercial tools,in regards to cutting forces,tool wear and surface quality.

Precision micro-milling process:state of the art

Micro-milling is a precision manufacturing process with broad applications across the biomedical,electronics,aerospace,and aeronautical industries owing to its versatility,capability,economy,and efficiency in a wide range of materials.In particular,the micro-milling process is highly suitable for very precise and accurate machining of mold prototypes with high aspect ratios in the microdomain,as well as for rapid micro-texturing and micro-patterning,which will have great importance in the near future in bio-implant manufacturing.This is particularly true for machining of typical difficult-to-machine materials commonly found in both the mold and orthopedic implant industries.However,inherent physical process constraints of machining arise as macromilling is scaled down to the microdomain.This leads to some physical phenomena during micromilling such as chip formation,size effect,and process instabilities.These dynamic physical process phenomena are introduced and discussed in detail.It is important to remember that these phenomena have multifactor effects during micro-milling,which must be taken into consideration to maximize the performance of the process.The most recent research on the micro-milling process inputs is discussed in detail from a process output perspective to determine how the process as a whole can be improved.Additionally,newly developed processes that combine conventional micro-milling with other technologies,which have great prospects in reducing the issues related to the physical process phenomena,are also introduced.Finally,the major applications of this versatile precision machining process are discussed with important insights into how the application range may be further broadened.

Cutting forces analysis of micro-milling process on Inconel 718-a finite element approach

This paper presents a modeling and simulation of micro-milling process with finite element modeling(FEM)analysis to predict cutting forces.The micro-milling of Inconel 718 is conducted using high-speed steel(HSS)micro-end mill cutter of 1mm diameter.The machining parameters considered for simulation are feed rate,cutting speed and depth of cut which are varied at three levels.The FEM analysis of machining process is divided into three parts,i.e.,pre-processer,simulation and post-processor.In preprocessor,the input data are provided for simulation.The machining process is further simulated with the pre-processor data.For data extraction and viewing the simulated results,post-processor is used.A set of experiments are conducted for validation of simulated process.The simulated and experimental results are compared and the results are found to be having a good agreement.

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.

State of the Art on Micromilling of Materials,a Review

The trend towards miniaturization has increased dramatically over the last decade, especially within the fields concerned with bioengineering, microelectronics, and aerospace. Micromillin8 is among the principal manu- facturing processes which have allowed the development of components possessing micrometric dimensions, being used to the manufacture of both forming tools and the final product. The aim of this work is to present the principal aspects related to this technology, with emphasis on the work material requirements, tool ma- terials and geometry, cutting forces and temperature, quality of the finished product, process modelling and monitoring and machine tool requirements. It can be noticed that size effect possesses a relevant role with regard to the selection of both work material （grain size） and tooling （edge radius）. Low forces and temper- ature are recorded during micromillin8, however, the specific cutting force may reach high values because of the ploughing effect observed as the uncut chip thickness is reduced. Finally, burr formation is the principal concern with regard to the quality of the finished part.

Potential damage threats to downstream optics caused by Gaussian mitigation pits on rear KDP surface

To determine whether a potassium dihydrogen phosphate(KDP)surface mitigated by micro-milling would potentially threaten downstream optics,we calculated the light-field modulation based on angular spectrum diffraction theory,and performed a laser damage test on downstream fused silica.The results showed that the downstream light intensification caused by a Gaussian mitigation pit of 800μm width and 10μm depth reached a peak value near the KDP rear surface,decreased sharply afterward,and eventually kept stable with the increase in downstream distance.The solved peak value of light intensification exceeded 6 in a range 8–19 mm downstream from the KDP rear surface,which is the most dangerous for downstream optics.Laser damage sites were then induced on the fused silica surface in subsequent laser damage tests.When the distance downstream was greater than 44 mm with a downstream light intensification of less than 3,there were no potential damage threats to downstream optics.The study proves that a mitigated KDP surface can cause laser damage to downstream optical components,to which attention should be paid in an actual application.Through this work,we find that the current manufacturing process and the mitigation index still need to be improved.The research methods and calculation models are also of great reference significance for related studies like optics mitigation and laser damage.

Mesoscale fabrication of a complex surface for integral impeller blades

Integral impeller is the most important compo- nent of a mini-engine. However, the machining of a mesoscale impeller with a complex integral surface is difficult because of its compact size and high accuracy requirement. A mesoscale component is usually manufac- tured by milling. However, a conventional milling tool cannot meet the machining requirements because of its size and stiffness. For the fabrication of a complex integral impeller, a micro-ball-end mill is designed in accordance with the non-instantaneous-pole envelope principle and manufactured by grinding based on the profile model of the helical groove and the mathematical model of the cutting edge curve. Subsequently, fractal theory is applied to characterize the surface quality of the integral impeller. The fractal theory-based characterization shows that the completed mesoscale integral impeller exhibits a favorable performance in terms of mechanical properties and morphological accuracy.

Nondestructive acquisition of the micro-mechanical properties of high-speed-dry milled micro-thin walled structures based on surface traits

Requirements for the service performance of aeronautic microelectronic components are increasingly strict.However,sever issues,that the acquisition of the service performance such as micro-mechanical properties is destructive,limit the subsequent application of the tested components.Addressing this issue,this paper proposes a nondestructive acquisition method of the micro-mechanical properties of the accelerometer micro-components,based on analyzing surface traits.To select qualified components without damage,we firstly developed a quasi-static microtensile tester and then established a combination prediction model of mechanical properties based on micro-milled surface traits.The model works due to the thin-walled structure,which makes the machined surface traits have significant influences on the mechanical properties such as Young’s modulus,yield strength,tensile strength,and elongation at break.Surface roughness,surface structure,and surface anisotropy are extracted to comprehensively present surface traits from different aspects.For improving the practicability of the model,the principal component analysis(PCA)is adopted to reduce high-dimensional traits explanatory variable space into two dimensions,and regression analysis models are comparative established in predicting the mechanical properties.Residuals analysis and error analysis are carried out to show the prediction accuracy.The maximum prediction error is about 10.62%,but the significance levels in the t-test of the predicted Young’s modulus and yield strength are not ideal.Therefore,kernel support vector regression(SVR)is imported to improve the prediction ability of the combination prediction model.The residuals analysis result shows that SVR is effective in enhancing the prediction ability of this model.