Surface Generation In Ultra-precision Machining Research Articles

Characterization of the Friction Coefficient of Aluminum Alloy 6061 in Ultra-Precision Machining

Aluminum alloy 6061(Al6061), an Al-Mg-Si alloy, is a precipitation-hardened alloy. The generation of precipitate affects its mechanical properties, and induces a worse surface finish during diamond cutting. The friction coefficients of the tool-chip and tool-workpiece interfaces influence temperature rise, and are therefore important predictors of tool wear and surface integrity during the diamond cutting of Al6061. This study investigated the relationship between precipitate generation and the friction coefficients of Al6061. Groups of experiments were conducted to study the influence of temperature and heating time on the number of precipitates and the friction coefficients. The results show that the generation of AlFeSi particles induces cracks, scratch marks and pits on diamond-machined Al6061 and affects the cutting forces. Moreover, the variation trend of the friction coefficient of Al6061 under different heating conditions agrees well with that of the number of AlFeSi particles. This implies that, during ultra-precision machining of precipitation-hardened alloys, cutting-induced heat causes precipitates to form on the chips and machined surface, changing their material properties. This affects the tool-workpiece and tool–chip contact conditions and the mechanisms of chip formation and surface generation in ultra-precision machining.

Microwave formation mechanisms in surface generation of ultra-precision machining

In ultra-precision machining (UPM), surface microwaves have been commonly produced on the machined surface along with lamellar chips. However, the intrinsic characteristics of surface microwave formation in UPM have not been understood well. Therefore, a theoretical and experimental investigation has been conducted into microwave formation mechanisms of surface generation in UPM. The results revealed that in UPM, the lamellar chip formation caused cyclic cutting forces to induce material recovery and tool vibration, namely chip formation induced material recovery and tool vibration. Accordingly, it caused surface microwaves on the machined surface. Further, a theoretical model has been developed qualitatively to represent the relationship between chip formation induced material recovery and tool vibration and surface microwaves. It was well identified by the machined and simulated surface topographies in UPM.

A theoretical and experimental study of forced spindle vibration under unbalanced magnetic forces in ultra-precision machining

In ultra-precision machining (UPM), a brushless permanent magnet DC motor employed for an air bearing spindle exhibits unbalanced magnetic forces (UMFs). The UMFs exert on the spindle rotor to induce forced spindle vibration, named UMFs induced forced spindle vibration (UMF-FSV). It would significantly deteriorate surface quality in UPM. However, the UMF-FSV is not well understood with its effect on surface generation in UPM. In this study, an analysis model of magnetic forces for a spindle motor is developed along with a surface generation model to study dynamics of UMF-FSV and its effect in UPM. The theoretical and experimental results signify that UMF-FSV is harmonic at a fundamental frequency 2pω (motor’s pole number 2p and spindle speed ω), which produces 2p straight radial patterns without phase shift at a machined surface in UPM.

An experimental investigation on surface generation in ultraprecision machining of particle reinforced metal matrix composites

Ultraprecision machining of metal matrix composites (MMCs) is observed as a scientific challenge, due to their hard-to-machine property and often the poor surface finish. This paper presents an experimental investigation on surface generation in ultraprecision machining of Al/B4C/50p MMCs. The machining trials using straight flute polycrystalline diamond (PCD) tools are conducted on a high precision micro milling machine. Side milling is adopted under varied cutting conditions. Metrology assessments on the workpiece surface roughness, topography, texture and defects/features are undertaken using a ZYGO 3D surface profiler and a scanning electron microscope (SEM). Experimental results indicate that process parameters and their contributions play essential roles in the machining process. By applying the optimal process parameters, e.g. cutting speed of 188.496 m/min, feed rate of 10 μm/rev and axial depth of cut of 150 μm, a better surface generation with surface roughness Ra < 20 nm can be obtained in ultraprecision machining of Al/B4C/50p particulate MMCs.

A generalized dynamic model for spindle vibration influencing surface topography in different ultra-precision machining processes

Ultra-precision machining (UPM) typically involves ultra-precision diamond turning (UPDT), ultra-precision raster milling (UPRM), and ultra-precision grinding (UPG). In UPM, spindle vibration (SV) is a natural feature majorly influencing surface topography. In this paper, a dynamic model for SV was generalized to study its distinctive effects on surface topography in different UPM processes. The theoretical results were identified well by a series of cutting tests. In UPDT, constant cutting forces induce harmonic SV to produce regular patterns. In UPRM, periodical impulsive cutting forces cause periodical impulsive SV to generate quasi-regular patterns. In UPG, random impulsive cutting forces result in partially random impulsive SV to form partially random patterns. The generalized model can be employed to predict the effects of SV on surface generation in UPM.

A Study of Effect of Cutting Strategy on Surface Generation in Ultra-Precision Machining of Micro-Structured Pattern Rollers

Plasticfilms with Embossed Micro-Structured Patterns have been Widely Used Inbacklight Guide Panels. the Mass Production of these Films Demands Forultra-Precision Roller Embossing of Micro-Structured Patterns on Plastic Filmsby Precision Pattern Rollers. due to the Heavy Workload and High Precisionrequirements, Ultra-Precision Rollers with Microstructures are very Difficultto be Machined in the Level of Submicrometer Form Accuracy and Surface Finishin Nanometer Range. this Paper Presents Theoretical and Experimental Studies Ofultra-Precision Machining of Precision Rollers with Microstructures. Themachining Mechanism for Precision Roller is Firstly Explained, and Hence Astudy of Effect of Cutting Strategies on Surface Generation in Ultra-Precisionmachining of Micro-Structured Pattern Rollers is Presented. this Includes Thestudy of Different Cutting Trajectories, Length-to-Diameter Ratio of Therollers, Mounting Method for the Rollers, the Number of Cuts in the Formationof the Micro-Structured Patterns, as well as the Time Budgeting for Adoptingdifferent Cutting Trajectories in Ultra-Precision Machining of Micro-Structuredpattern Rollers. the Results of the Study Provide an Important Means Forenhancing the Surface Quality and Optimizing the Time for Machining Precisionrollers.

Analysis of surface generation in ultra-precision machining with a fast tool servo

The fast tool servo (FTS) is one of the emerging ultra-precision machining technologies for the fabrication of high-quality optical microstructural surfaces. The diamond tool is fixed on the FTS, which is activated back and forth by a stacked type piezoelectric actuator. Optical microstructures with sub-micrometre form accuracy and nanometric surface finish can be fabricated without the need for any subsequent post processing. However, current understanding of the cutting mechanics and the factors affecting the surface generation in FTS machining is still far from complete. Although there has been some research work conducted to fill the research gaps with respect to FTS machining, most of the previous studies have been focused on the design of FTS for better performance and modelling characteristic of FTS actuators. The study of the process factors affecting surface generation in FTS machining has received little attention. As a result, this paper aims to analyse the effects of process parameters on surface generation in FTS machining. The factors being studied include spindle speed, feed rate, and depth of cut. A series of cutting experiments was carried out under various cutting conditions and the surface quality of the workpiece in terms of the form error and form defects were studied. Based on the results of the investigation, some recommendations for optimizing surface quality in the FTS machining process are discussed.

A kinematics and experimental analysis of form error compensation in ultra-precision machining

Ultra-precision machining has drawn much attention and the error compensation is an essential issue for improving the accuracy of the machining process. However, the analysis of kinematics errors on the surface generation in ultra-precision machining has received relatively little attention. Ultra-precision machine can be represented as a multi-body system. Based on the theory of multi-body system, a kinematics model of two-axis ultra-precision machining system has been developed in the present study. Hence, a software error compensation method is incorporated which is carried out by modifying the idea tool path in the NC program. The modified NC program takes into account the kinematics error factors and so the actual tool path generation can be compensated for the kinematics errors on the machining of the surface of the workpiece. To verify the theoretical kinematics model and the error compensation method, a series of machining experiments have been conducted and the experimental results indicate that better surface quality was achieved with the implementation of the proposed compensation method.

A novel robust Gaussian filtering method for the characterization of surface generation in ultra-precision machining

A lot of research work has been focused on the study of the surface generation mechanisms in order to predict the surface topography and provide the optimal machined parameters based on the experiential understanding of relationship of machined conditions and surface features. Although the formation of novel geometrical product specification (GPS) and verification framework system promotes the relevant research work to new characterization methods and draft of international standards, relative little research work was conducted on the application of surface characterization techniques to ultra-precision machining which is very important to evaluate the surface quality. In this paper, a novel robust Gaussian filtering method (RGF) is proposed and used to characterize the surface topography of ultra-precision machined surfaces. Cubic B-spline and M-estimation are used to make the method reliable and robust. Based on the property comparisons of classical weighting functions, a novel auto-developed robust weighting function (ADRF) is defined to improve the robustness of RGF. To verify the characterization feasibility of the proposed method, computer simulation is used and then the real ultra-precision machined surfaces are analyzed. The experimental results indicate that the RGF method cannot only separate the surface components effectively on the whole measured area and but also eliminates the influence of freak outliers.

Surface characterization in ultra-precision machining of Al/SiC metal matrix composites using data dependent systems analysis

This paper presents a data dependent systems (DDSs) method for the analysis of surface generation in ultra-precision machining of Al/SiC metal matrix composites (MMCs). The DDS analysis provides a component by component wavelength decomposition of the surface roughness profile of the machined surface. A series of face cutting experiments was done on Al6061/15SiCp MMCs under different cutting conditions. The cutting results indicate that the characteristics of the wavelength components analyzed by the DDS analysis method are correlated well with the surface generation mechanisms. Since the relative powers of the wavelength components are used to measure the contributions of the cutting mechanisms to the total roughness, this resolves the shortcomings of the conventional spectrum analysis method in characterizing the surface properties such as pits and cracks in ultra-precision machining of MMCs.

A dynamic surface topography model for the prediction of nano-surface generation in ultra-precision machining

Materials induced vibration has its origin in the variation of micro-cutting forces caused by the changing crystallographic orientation of the material being cut. It is a kind of self-excited vibration which is inherent in a cutting system for crystalline materials. The captioned vibration results in a local variation of surface roughness of a diamond turned surface. In this paper, a dynamic surface topography model is proposed to predict the materials induced vibration and its effect on the surface generation in ultra-precision machining. The model takes into account the effect of machining parameters, the tool geometry, the relative tool–work motion as well as the crystallographic orientation of the materials being cut. A series of cutting experiments was performed to verify the performance of the model and good correlation has been found between the experimental and simulation results.

Development of a lifting wavelet representation for surface characterization

This paper reviews the existing numerical analysis methods and their problems in surface metrology. Based on the requirements of functional analysis of surfaces, this paper proposes a lifting wavelet representation for extraction of different components of a surface. The theory of the lifting wavelet is introduced and a fast algorithm is developed. Different frequency components of the surface can be separated, extracted and then reconstructed according the intended requirements of functional analysis. The surface textures can be highlighted and multi-scalar topographical features can be identified and clearly recovered. In order to verify the behaviour of the new model, a computer simulation based on sinusoidal and triangular waveforms is used. Case studies are conducted using a series of typical surfaces of engineering and bioengineering, such as planes, cylinders and curves, measured by contact (stylus) and non-contact (phase-shifting interferometry) instruments, to demonstrate the feasibility and applicability of using the lifting wavelet model in the analysis of these surfaces.