Status of research on non-conventional technology assisted single-point diamond turning

With the increasing use of difficult-to-machine materials in aerospace applications,machining requirements are becoming ever more rigorous.However,traditional single-point diamond turning(SPDT)can cause surface damage and tool wear.Thus,it is difficult for SPDT to meet the processing requirements,and it has significant limitations.Research indicates that supplementing SPDT with unconventional techniques can,importantly,solve problems due to the high cutting forces and poor surface quality for difficult-to-machine materials.This paper first introduces SPDT and reviews research into unconventional techniques for use with SPDT.The machining mechanism is discussed,and the main advantages and disadvantages of various methods are investigated.Second,hybrid SPDT is briefly described,which encompasses ultrasonic-vibration magnetic-field SPDT,ultrasonic-vibration laser SPDT,and ultrasonic-vibration cold-plasma SPDT.Compared with the traditional SPDT method,hybrid SPDT produces a better optical surface quality.The current status of research into unconventional techniques to supplement SPDT is then summarized.Finally,future development trends and the application prospects of unconventional assisted SPDT are discussed.

Simulation and experiment analysis on thermal deformation of tool system in single-point diamond turning of aluminum alloy

The aim of this work is to simulate thermal deformation of tool system and investigate the influence of cutting parameters on it in single-point diamond turning(SPDT) of aluminum alloy. The experiments with various cutting parameters were conducted. Cutting temperature was measured by FLIR A315 infrared thermal imager. Tool wear was measured by scanning electron microscope(SEM). The numerical model of heat flux considering tool wear generated in cutting zone was established. Then two-step finite element method(FEM) simulations matching the experimental conditions were carried out to simulate the thermal deformation. In addition, the tests of deformation of tool system were performed to verify previous simulation results. And then the influence of cutting parameters on thermal deformation was investigated. The results show that the temperature and thermal deformation from simulations agree well with the results from experiments in the same conditions. The maximum thermal deformation of tool reaches to 7 μm. The average flank wear width and cutting speed are the dominant factors affecting thermal deformation, and the effective way to decrease the thermal deformation of tool is to control the tool wear and the cutting speed.

Application of pre-alloyed powders for diamond tools by ultrahigh pressure water atomization

Copper, iron and cobalt based pre-alloyed powders for diamond tools were prepared by ultrahigh pressure water atomization（UPWA） process. Pre-alloyed powders prepared by different processes including UPWA, conventional water atomization （CWA） and elemental metal mechanical mixing （EMMM） were sintered to segments and then compared in mechanical properties, holding force between matrix and diamond, fracture morphology of blank and sintering diamond section containing matrix. The results showed that the pre-alloyed powder prepared by UPWA exhibits the best mechanical properties including the relative density, the hardness and the bending strength of matrix sinteredsegment. Sintered segments fractography of UPWA pre-alloyed powder indicatesmechanical mosaic strength and chemical bonding force between the pre-alloyed powder and the diamond, leading to the great increase in the holding force between matrix and diamond. The mechanical performance andthe service life of diamond tools were greatly improved by UPWA pre-alloyed powders.

SURFACE ROUGHNESS PREDICTION MODEL FOR ULTRAPRECISION TURNING ALUMINIUM ALLOY WITH A SINGLE CRYSTAL DIAMOND TOOL

A surface roughness model utilizing regression analysis method is developedfor predicting roughness of ultra-precision machined surface with a single crystal diamond tool. Theeffects of the main variables, such as cutting speed, feed, and depth of cut on surface roughnessare also analyzed in diamond turning aluminum alloy. In order to predict the optimum cuttingconditions during process planning. A lot of experimental results show that the model can predictthe surface roughness effectively under a certain cutting conditions.

Tool Wear and Its Effect on Surface Roughness in Diamond Cutting of Glass Soda-lime

For the technology of diamond cutting of optical glass, the high tool wear rate is a main reason for hindering the practical application of this technology. Many researches on diamond tool wear in glass cutting rest on wear phenomenon describing simply without analyzing the genesis of wear phenomenon and interpreting the formation process of tool wear in mechanics. For in depth understanding of the tool wear and its effect on surface roughness in diamond cutting of glass, experiments of diamond turning with cutting distance increasing gradually are carried out on soda-lime glass. The wear morphology of rake face and flank face, the corresponding surface features of workpiece and the surface roughness, and the material compositions of flank wear area are detected. Experimental results indicate that the flank wear is predominant in diamond cutting glass and the flank wear land is characterized by micro-grooves, some smooth crater on the rake face is also seen. The surface roughness begins to increase rapidly, when the cutting mode changes from ductile to brittle for the aggravation of tool wear with the cutting distance over 150 m. The main mechanisms of inducing tool wear in diamond cutting of glass are diffusion, mechanical friction, thermo-chemical action and abrasive wear. The proposed research makes analysis and research from wear mechanism on the tool wear and its effect on surface roughness in diamond cutting of glass, and provides theoretical basis for minimizing the tool wear in diamond cutting brittle materials, such as optical glass.

Effects of rare earth element lanthanum on the microstructure of copper matrix diamond tool materials

Effects of rare earth element La on the microstructure of Cumatrix diamond tools were researched under the conditions of variousmaterials components and the process parameters in order to improvematerials properties. SEM, XPS and X-ray were used to investigate thefracture section, microstructure and the element valence inmaterials. The Results shown that the combination of rare earthelement La and transition element Ti is advantageous to the bondingstate Between diamond particles and matrix, so it can improve thematerials properties. Suitable sintering temperature is 790 deg. C.

A study on comprehensive recycling of waste diamond tools

This article puts forward a new method of recycling materials in diamond tools comprehensively and efficiently by means of analyzing and summarizing various methods of recycling waste diamond tools.After the waste diamond tools were decomposed in a mixed acid,metals contained in it went into solution in their ionic forms,while diamond and tungsten carbide particles formed into residues to be reclaimed.The amounts of metal ions in the leaching solution were adjusted according to the contents of metals in the diamond tools;then,the leaching solution was co-precipitated using oxalic acid as precipitation agent,and ammonia water was added to adjust the pH value of the oxalic acid.Under the right conditions,the comprehensive precipitation rate of metals reached above 98%.Finally,ultrafine pre-alloy powder was obtained by hydrogen reduction of oxalate.

Properties of diamond tool binders with fine carbonyl Ni powder additions

Fine Ni powder is often added to Co and bronze-based metal binder powders for diamond tool segments.Ni is a lower cost substitute for extra-fine Co powder and increases the toughness of Co-Fe diamond binders at the expense of lower hardness and bend strength.In bronze-based diamond binder segments,Ni increases hardness and yield strength.Several grades of Ni powder are used commercially with both Co and bronze-based diamond binders.This paper compares properties of diamond binders containing carbonyl Ni powders including standard Inco(?) T255,T123 PM and T 110 PM.Binder materials were made by ball milling or dry mixing of the fine carbonyl Ni and Fe powders with either XF Co or air atomized bronze(90/10 Cu/Sn) powders.Co-based powder blends were hot pressed at 20～35 MPa and 700℃to 900℃.Bronze-based powder blends were cold pressed and sintered at 840℃.Apparent density,apparent hardness and bend strength(TRS) were compared for different binder compositions and processing conditions.

Approach for Polishing Diamond Coated Complicated Cutting Tool: Abrasive Flow Machining(AFM)

Lower surface roughness and sharper cutting edge are beneficial for improving the machining quality of the cut?ting tool, while coatings often deteriorate them. Focusing on the diamond coated WC?Co milling cutter, the abrasive flow machining(AFM) is selected for reducing the surface roughness and sharpening the cutting edge. Comparative cutting tests are conducted on di erent types of coated cutters before and after AFM, as well as uncoated WC?Co one, demonstrating that the boron?doped microcrystalline and undoped fine?grained composite diamond coated cutter after the AFM(AFM?BDM?UFGCD) is a good choice for the finish milling of the 6063 Al alloy in the present case, because it shows favorable machining quality close to the uncoated one, but much prolonged tool lifetime. Besides, compared with the micro?sized diamond films, it is much more convenient and e cient to finish the BDM?UFGCD coated cutter covered by nano?sized diamond grains, and resharpen its cutting edge by the AFM, owing to the lower initial surface roughness and hardness. Moreover, the boron incorporation and micro?sized grains in the underly?ing layer can enhance the film?substrate adhesion, avoid the rapid film removal in the machining process, and thus maximize the tool life(1040 m, four times more than the uncoated one). In general, the AFM is firstly proposed and discussed for post?processing the diamond coated complicated cutting tools, which is proved to be feasible for improving the cutting performance

Wear characteristics of Ⅴ shape diamond tool for micro prism pattern with Al alloys

The ultra-precision machining process using a single crystal diamond tool has been mainly used for machining molds of optical components.Since the micro patterns of various shapes having excellent surface roughness can be machined by using ultra-precision machine tools,the micro pattern on a large light guide plate (LGP) is mainly machined using a diamond tool.The tool wear occurs due to long machining distances and time while machining a large-area LGP mold.The deformation and dimensional error of micro pattern are caused by tool wear,as a result,the light efficiency of LGP declines.The characteristics of tool wear should be analyzed in order to precisely machine large-area LGP mold from all sorts of materials.The experiments were performed in order to compare wear characteristics of a V90° diamond tool using Al3003,5052,6061 and 7075.The prism pattern of depth 10 μm was machined in order to analyze characteristics of tool wear according to machining distances (0.5,1 and 1.5 km).The effects of tool wear on pattern shape were analyzed by applying overlapped cutting depths (Rough machining is (10+8+7) μm and Finish machining is (5+3+2+1) μm) by continuously machining a prism pattern of W shape of 25 μm in depth.

STUDY ON COATING MECHANISM OF DIAMOND FILM ON CUTTING TOOL AND ITS APPLICATION

The deposition mechanism of diamond film on cutting tools and the state of the interface between film and substrate are studied theoretically and experimentally. Methods for controlling diamond crystalline state and improving adhesion of diamond films to substrates are proposed to improve the quality of diamond-coated tools. Experiments are performed by cutting Al-Si18% alloy and SiCp/Al composite with diamond coated tool. The results indicate that the life of coated tools is 90 times higher than that of non-coated tools. Wear mechanism of diamond-coated tools is also studied.

TOOL FORCE MODEL FOR DIAMOND TURNING

A new tool force model to be presented is based upon process geometry and thecharacteristics of the force system, in which the forces acting on the tool rake face, the cuttingedge rounding and the clearance face have been considered, and the size effect is accountable forthe new model. It is desired that the model can be well applicable to conventional diamond turningand the model may be employed as a tool in the design of diamond tools. This approach is quitedifferent from traditional investigations primarily based on empirical studies. As the depth of cutbecomes the same order as the rounded cutting edge radius, sliding along the clearance face due toelastic recovery of workpiece material and plowing due to the rounded cutting edge may becomeimportant in micro-machining, the forces acting on the cutting edge rounding and the clearance facecan not be neglected. For this reason, it is very important to understand the influence of someparameters on tool forces and develop a model of the relationship between them.

A critical review on the chemical wear and wear suppression of diamond tools in diamond cutting of ferrous metals

Diamond tools play a critical role in ultra-precision machining due to their excellent physical and mechanical material properties,such as that cutting edge can be sharpened to nanoscale accuracy.However,abrasive chemical reactions between diamond and non-diamond-machinable metal elements,including Fe,Cr,Ti,Ni,etc,can cause excessive tool wear in diamond cutting of such metals and most of their alloys.This paper reviews the latest achievements in the chemical wear and wear suppression methods for diamond tools in cutting of ferrous metals.The focus will be on the wear mechanism of diamond tools,and the typical wear reduction methods for diamond cutting of ferrous metals,including ultrasonic vibration cutting,cryogenic cutting,surface nitridation and plasma assisted cutting,etc.Relevant commercially available devices are introduced as well.Furthermore,future research trends in diamond tool wear suppression are discussed and examined.

Research progress of nickel based filler for development of diamond tools

Owing to diamond excellent physical and chemical properties,so synthetic diamond abrasives are extensively used in manufacturing diamond tools are utilized in machining hard and brittle materials.The brazing technology is exploited with strong bonding force between the diamond and substrate,which can realize metallurgical and chemical bonding between the filler metals and diamond abrasives.In this paper,the research reports on nickel-based fillers for brazing diamond grains at home and abroad in recent years are reviewed systematically,with emphasis on the influence of alloying elements and active elements on the properties of nickel-based fillers.The advantages and disadvantages of Cr,B,Si,P,Mn,Fe,Cu,W,C in nickel-based fillers and the negative effects of impurity elements were summarized.The shortcomings in the research and application of nickel-based fillers were pointed out,which provided theoretical guidance for further systematic research and development of related technologies.

Experimental Investigation and Numerical Simulation on Interfacial Carbon Diffusion of Diamond Tool and Ferrous Metals

We numerically simulated and experimentally studied the interfacialcarbon diffusion between diamond tooland workpiece materials.A diffusion modelwith respect to carbon atoms of diamond toolpenetrating into chips and machined surface was established.The numericalsimulation results of the diffusion process revealthat the distribution laws of carbon atoms concentration have a close relationship with the diffusion distance,the diffusion time,and the originalcarbon concentration of the work material.In addition,diamond face cutting tests of die steels with different carbon content are conducted at different depth of cuts and feed rates to verify the previous simulation results.The micro-morphology of the chips is detected by scanning electron microscopy.Energy dispersive X-ray analysis was proposed to investigate the change in carbon content of the chips surface.The experimentalresults of this work are of benefit to a better understanding on the diffusion wear mechanism in single crystaldiamond cutting of ferrous metals.Moreover,the experimentalresults show that the diffusion wear of diamond could be reduced markedly by applying ultrasonic vibration to the cutting toolcompared with conventionalturning.

New Nanocrystalline Matrix Materials for Sintered Diamond Tools

The work presents the possibility of substitution of expensive, wear resistant Co-WC powders, that have been traditionally used in the production of sintered diamond tools, with cheap iron-base counterparts manufactured by ball milling. It has been shown that ball-milled Fe-Ni-Cu-Sn-C powders can be consolidated to a virtually pore-free condition by hot pressing at 900 ℃. The as-consolidated material has nanocrystalline structure and is characterised by a combination of high hardness, mechanical strength and excellent resistance to abrasion. Its properties can be widely modified by changing the milling conditions.

High temperature brazing of diamond tools

A new brazing technique of diamond was developed. Using this new technique optimum chemical and metallurgical bonding between the diamond grits and the carbon steel can be achieved without any thermal damages to diamond grits. The results of microanalysis and X-ray diffraction analysis reveal that a carbide layer exists between the diamond and the matrix, which consists of Cr3C2, Cr7C3 and Cr23C6. Performance tests show that the brazed diamond core-drill has excellent machining performance. In comparison with traditional electroplated diamond core-drill, the brazed diamond core-drill manufactured using the new developed technique has much higher machining efficiency and much longer operating life.

A Fast Tool Servo System for Fabrication of Micro-structured Surfaces on A Diamond Turning Machine

A fast tool servo (FTS) system is developed for the fabrication of non-rotationally symmetric micro-structured surfaces using single-point diamond turning machines.The constructed FTS employs a piezoelectric tube actuator (PZT) to actuate the diamond tool and a capacitive probe as the feedback sensor.To compensate the inherent nonlinear hysteresis behavior of the piezoelectric actuator,Proportional Integral (PI) feedback control is implemented.Besides,a feed-forward control based on a simple feed-forward predictor has been added to achieve better tracking performance.Experimental results indicate that error motions in the performance of the system caused by hysteresis can be reduced greatly and the micro-structured surface is successfully fabricated by implementing the FTS.

CURING PROCESS OF PHOTOPOLYMER RESIN BOND DIAMOND TOOLS

Analytical simulation and corresponding proof-test are adopted to study the principle of the curing process of photopolymer resin diamond tools. The influence of the diamond as abrasives in photopolymer resin owing to the absorptivity of the diamond for the UV light on the photopolymer resin curing process is discussed. Based on the above, a kind of diamond tool—dicing blade is selected to analyze the curing process of photopolymer bond diamond tools. An analytical model of curing process is developed and a correlation curve between the depth of polymerization of the photopolymer resin diamond tools and the exposure time to represent the curing process of photopolymer bond dicing blade. A test is done to proof-test the validity of the analytical model and the correlation curve. The simulated data fit the experimental results, which demonstrates the analytical models and numerical algorithm are of high reliability. The analytical simulation method could possibly be used to optimize the curing cycle and improve the quality of the photopolymers resin bond diamond tools.

An Indentation Method for Nanoprecision Measurement of Diamond Tool Edge Radius

In ductile mode cutting of brittle materials using di amond tools, such as ductile cutting of silicon and quartz for wafer fabrication , one of the key conditions for achieving ductile chip formation is to get the r ight ratio of tool cutting edge radius to the undeformed chip thickness. It has been shown that the undeformed chip thickness has to be in the order of nanomete rs and that the tool cutting edge radius has to be smaller than the undeformed c hip thickness. Therefore, nanoprecision measurement of diamond cutting tools has become a key issue for ductile mode cutting of brittle materials. In this paper , a non-destructive nanoprecision measurement method for diamond tool cutting e dge radius is presented. The basis of the method is that the exact profile of th e tool cutting edge can be perfectly copied by indenting the tool cutting edge o n the surface of a rigid-perfect plastic material, and that the copy of the pro file can be measured at nanoprecision level. Ideally, the first aspect of th e method is to make a perfect copy of the tool cutting edge profile by indentati on on the surface of a rigid-perfect plastic material which has no elastic spri ng back, so that a true copy of the tool cutting edge is maintained for subseque nt measurement. Since no rigid-perfect plastic material can be found in realit y, actual materials of rigid-elastic-plastic nature have to be used for the in dentation in the measurement method, and the material elastic error compensation coefficients have to be determined to cancel out the effect of elastic spring b ack. For the minimization of error compensation, criteria for the selection of t he optimal materials for the indentation measurement are found to be: 1) high ri gidity and high density, 2) large Young’s elastic modulus, and 3) low yield strength. One of such materials identified is copper. The second aspect of the method is to measure the radius of the indented profile on the surface of the ma terial. This can be achieved by using an atomic force microscope (AFM), and in t his paper the results for measurement of diamond tool edge radii of nanometer sc ales by indentation on a copper material are presented. The elastic error compen sation coefficient for the copper material is determined through the indentation of a tungsten carbide tool edge on the copper surface. By comparing the actual tool edge radius measured using SEM on the sectional view of the tungsten carbid e tool with the one measured from the copied profile of the tool edge on the cop per surface, the coefficient is obtained. Analysis is given for the accuracy of the proposed method, showing that as far as the elastic compensation coefficient is consistent with the material used for the indentation measurement, the only source of errors with the measurement will come from the device for measuring th e indented profile on the surface of the solid, in this case it will come from t he AFM which measures on the sub-nanometer scales.