Diamond Tool Wear Research Articles

The wear of polycrystalline diamond tools used in the cutting of metal matrix composites

Polycrystalline diamond (PCD) has been used for some years for the machining of abrasive systems such as aluminium/silicon and glass filled polymeric materials. This paper reports on the machining of the highly abrasive composite system of aluminium reinforced by silicon carbide particles and/or alumina fibres using polycrystalline diamond tools. The results indicate that polycrystalline diamond tooling offers superior performance over carbide, both in wear resistance and the quality of the surface finish produced. Observations of the morphology of the wear scars on the tools indicate that the wear process involves both adhesive wear and of the build up of defects within the diamond particles leading to eventual micro- and macro-fracture in a fatigue-like process.

Development of monitoring system on the diamond tool wear

Recently, ultra-precision machining using a single crystal diamond tool has been developing very rapidly, especially in the fields of production processes for optical or magnetic parts such as magnetic discs, laser mirrors, polygon mirrors and copier drums. As a result, it has been successfully extended to machine various soft materials, generating mirror-like surfaces to sub-micron geometric accuracy with the ultra-precision CNC machine and the single crystal diamond tool. With the real cutting operation, the geometric accuracy and the surface finish attainable in machined surfaces are mainly determined by both of the sharpness of a cutting tool and stability of the machine vibration. In this study, for monitoring the progress of machining state for assuring the machining accuracy and the surface quality, a new monitoring method of machining states in face-cutting with diamond tool is proposed, using the frequency response of multi-sensors signal, which includes wear state of tool in terms of the energy within the specific frequency band. A magnetic disc is machined on the ultra-precision lathe.

Investigation of Cutting Temperature and Tool Wear in Diamond Cutting of Glasses

Glasses are difficult to machine by single point diamond turning as the tool wear is relatively rapid. In this paper, a diamond cutting test was carried out to investigate the wear mechanism of diamond cutting tools. The tool tip temperature was measured by a thermovision scanner. The effect of cutting speed on the tool temperature was analyzed by a proposed model. Analytical results compare well with the experimental data. The tool wear mechanism was studied based on the measured data of cutting temperature, machined surface roughness, and the microstructure analysis of the wear zone. Cleavage and microchipping appear to be the dominant wear mechanisms of diamond tools under the cutting conditions used in the test. Methods for minimizing tool wear and hence improving the machined surface quality are also discussed.

Wear of Polycrystalline Diamond Tool in Cutting of SiC Grain Reinforced Plastic. Influence of Grain Sizes of SiC and Diamond.

The wear of a polycrystalline diamond tool in the cutting of a SiC grain-reinforced plastic composite is investigated. The effects of grain sizes of SiC in the composite and the diamond of the tool were concerned. The cutting experiments showed that higher wear of the tool occurs in cutting of the composite with larger SiC grains; the coarse-grained tool exhibits a higher wear resistance than the corresponding fine-grained one for all composites. Moreover, tool wear is increased drastically when the SiC grains are larger than the tool grains. On the other hand, a wear called the tear-off model, was proposed to explain the wear mechanism of polycrystalline diamond tools in cutting the SiC-plastic composite. The model illustrated that the greater wear of the tool with the larger SiC grains call be attributed to the iscrease in debonding force of a SiC grain. Finally, an empirical relation, introduced as a fatigue-like curve, between the maximum stress on the tool grains and the number of stress cycles was established to describe the generalized relationship between the SiC grain size in the composite and the flank wear of the tool, taking into consideration the SiC volume ratio, SiC size and tool grain size.

Chemical aspects of tool wear in single point diamond turning

A hypothesis is proposed that ascribes chemical wear of diamond tools to the presence of unpaired d electrons in the sample being machined. This hypothesis is used to explain a range of results for metals, alloys, and other materials including “electroless” nickel. The hypothesis is further tested by experiments presented here on the machining of a range of high purity elements. The implications for diamond turnability of other materials are discussed.

Energy scaling transitions in machining of silicon by diamond

The existence of an energy scaling brittle-ductile transition in the machining of ceramics and glasses is now well established. We have examined the surface layers of silicon crystals machined in the ductile regime by two methods: (i) a dedicated highly stiff single point diamond turning facility (SPDT), using cut depths of the order of 100 nm (ii) high precision cup grinding using a nominal cut depth of 500 nm. Surfaces were profiled by AFM and subsurface damage was characterized by Rutherford ion backscattering and cross section TEM. The main results to date are: (a) The SPDT specimens possessed a surface quality corresponding to that achieved by optical polishing, the R a ⋍ 0.6 nm and R max (P-V) ⋍ 6 nm. (b) The R a values of the ground specimens ranged between 7 nm and 20 nm, with 64 < R max < 148 nm. There were significant differences between wheels bonded by resin and by cast iron. (c) The mean depths of surface damage were in the range 200–400 nm in all cases. (d) In the SPDT crystals the subsurface damage consisted of dislocation loops intersecting the surface. In any one region of the specimen these represented slip on a single close packed system. (e) In ground slices the permanent damage comprised sub-micron length cracks as well as a high density of dislocations on various systems. Local regions of amorphous silicon were also present. (f) In SPDT ductile machining diamond tool wear is effectively homogeneous and much less variable than in normal machining.

Tool Wear Monitoring in Diamond Turning by Fuzzy Pattern Recognition

This paper introduces a fuzzy pattern recognition technique for monitoring single crystal diamond tool wear in the ultraprecision machining process. Selected features by which to partition the cluster of patterns were obtained by time series AR modeling of dynamic cutting force signals. The wear on a diamond tool edge appears to be classifiable into two types, micro-chipping and gradual, both very small compared to conventional tool wear. In this regard, we used a fuzzy technique in pattern recognition, which considers the ambiguity in classification as well as the weakness of the cutting force variation, to monitor the diamond tool wear status, with satisfactory results.

Evaluation of wiredrawing tool strength

We propose a technique for evaluating wiredrawing tool strength that is based on the numerical finite element method (FEM) and makes it possible to obtain the stress, strain, and displacement fields through the volume of the tool and analyze the influence of the process parameters on the stress state. We identify the causes of wear and possible failure of hard-alloy and diamond wiredrawing tools. Recommendations are made for improving the wear resistance and service life of the wiredrawing tool, and the possibility of reducing the volume of the hard-alloy and diamond drawing dies used in production is shown.

Wear of monocrystalline diamond tools during ultraprecision machining of nonferrous metals

In studying the wear behavior of diamond cutting tools, a pragmatic appraoch has been chosen in which the tool wear and the change in cutting forces have been specifically determined as a function of tool life. Several nonferrous metals, such as copper, aluminium, and electroless nickel, have been machined. The influence of microstructural characteristics, crystallographic orientation, and mechanical surface state of diamonds on tool-wear behavior is investigated in considerable detail. It has been found that wear behavior of diamond tools depends strongly on workpiece material, so that when machining aluminium, all types of diamond show considerable and almost the same degree of wear. However, machining copper and electroless nickel entails much subtler wear characteristics; in fact, great differences in wear resistance between different types of diamonds were discerned. Type all diamonds in particular, both synthetic and natural, appear to be highly resistant to wear. The best crystallographic orientation for wear-resistant diamonds depends on the way the cutting tools are used.

Fuzzy Pattern Recognition for Tool Wear Monitoring in Diamond Turning

Abstract In this paper, to monitor single crystal diamond tool wear in ultraprecision machining process, a fuzzy pattern recognition technique was introduced. Some selected features to partition the cluster of pattern were obtained from time series AR modeling of dynamic cutting force signals. The wear on a diamond tool edge appears to be classifiable into two types, one of which is micro-chipping and the other gradual, both very small quantities to detect compared to conventional tool wear. In this regard, a fuzzy technique in pattern recognition, which considers the ambiguity in classification as well as the weakness of the cutting force variation, was used for monitoring the diamond tool wear status.

Cryogenic Diamond Turning of Stainless Steel

Tool wear is extremely rapid when ferrous materials are single point diamond turned. This paper reviews diamond tool wear mechanisms, showing that both fracture and chemical mechanisms may be important. The rate of all chemical reactions increases exponentially with temperature. Hence tool wear may be reduced significantly by machining at cryogenic temperatures. A cryogenic machining system comprising tool post and chuck with constrained liquid nitrogen flows has been built. Using this system a number of 35 mm diameter, 400 series stainless steel flats have been diamond turned. Surface finish is better than 25 nm Ra.

超精密切削用ダイヤモンド工具の長寿命化 無電解Ｎｉ‐Ｐの超精密切削加工に関する研究

This research is primarily aimed at the longer tool life of natural single crystal diamond in ultra precision for an electroless nickel phosphorus plating. The following results have been obtained : (1) The profile to increase of the tool life drawn from this work is that back and side rake angle were formed at -5 with nose radius 0.76mm and other tool dimensions has constant values. (2) The groove wear of natural single diamond tool is grown by asperity of tool feed mark on the ultra precision machined surface. (3) The typical tool wear of diamond shows an attrition wear without a chipping failure in the optimum tool profile.

A Study on Diamond Turning of Al-Mg Alloy — Generation Mechanism of Surface Machined with Worn Tool

It is well-known that the roughness of machined surfaces in diamond turning can be improved with increase of cutting length in comparison with that of the initial stage. This seems to result from an apparent increase in the wear of the diamond tool with cutting length. In this paper, the effect of diamond tool wear on surface roughness is examined for the turning of an Al-Mg alloy. The following results are obtained. (1) The tears generated on the leading end cutting edge of a straight tool deteriorate the surface roughness at a positive tool setting angle. Conversely, the tear marks decrease as the tool wear grows. (2) The surface roughness has a strong correlation with the cutting edge recession of the worn tool. (3) A residual stock removal is generated at a cutting edge recession of more than 0.3μm. Since uneven residual stock removal with tear marks is cut off by the trailing end cutting edge, the surface roughness is improved after a certain cutting length.

Diamond Turning of an Aluminum Alloy for Mirror

Summary The paper deals with the life, the wear of single crystal diamond tools and their effects on the micro-roughness and the residual stress of the surface layers, under various machining conditions. Three kinds of diamond tools, having different nose radii, were used for mirror finishing of aluminum alloy workpieces. Cutting tests were carried out untill the cutting distance of a tool reached to 900Km. Despite of tool wear, the roughness of diamond-turned surface remains almost constant due to the burnishing effects. The micro-roughnesses are more or less varied by the feed rate and the nose radius of the cutting edge. Also the micro-roughness relate closely with the thrust forces. X-ray diffraction analysis was also conducted to determine the residual stress for each process. In the mirror finishing process, compressive stress of about 60 MPa remains on the surface layers. The thickness of the work-affected layer is merely on the order of submicrometers.

Increasing productivity during grinding of high-alumina ceramics

The grinding of high-alumina ceramics involves specific problems as the effectiveness of the grinding is affected by the rate of material removal to ensure high productivity, the surface roughness, and the wear of the diamond tool. This study of the cutting processes in cylindrical and internal grinding was done to determine the optimum cutting parameters and specifications of the diamond grinding wheels, and the results helped increase productivity and reduce wheel consumption.

Some observations on the wear of single point diamond tools used for machining glass

The wear pattern on a single point diamond tool used for machining glass is studied. Possible wear mechanisms are proposed on the basis of additional sliding wear tests and observations by scanning electron and optical microscopy. The wear process is believed to take place in two stages, one involving a polishing mechanism and the other consisting of crack propagation which occurs after the accumulation of a certain amount of damage. The importance of the crystallographic orientation of the diamond single crystal, particularly for crack propagation along cleavage planes is pointed out. It is concluded that the likelihood of rapid deterioration of the diamond tool may be decreased by proper crystallographic orientation.

The wear of diamond tools turning mild steel

Previous experiments on the wear of diamond tools turning mild steel have shown that the very high rates of wear of the diamond arise from the degeneration of the diamond to graphite, the details of the wear mechanisms depending on the cutting conditions. The present experiments on a larger number of tools show much greater differences in the wear rates of different diamonds than have been reported previously. It appears probable that these differences in wear rates arise from differences in the chemical constitution of the diamonds.

Tool wear and solid state reactions during machining

Measurements have been made of the wear of diamond tools turning mild steel under a range of carefully specified conditions. High rates of wear are observed owing to graphitization of the diamond. Under certain conditions, this graphitization may proceed at a considerable rate even if there is no appreciable temperature rise at the diamond-steel interface. This result implies that the clean surfaces generated by the machining process have chemical activities different from those of the bulk material. Examples of unusual chemical activity have also been observed when using diamond tools to turn other metals, when using tungsten tools to turn graphite, and copper and nickel tools to turn sulphur. The experiments show that machining, under suitable conditions, offers a precise method of measuring rates of reaction between clean solids and of obtaining information on the relative bond strengths of the surface atoms.

Some aspects of the wear of polycrystalline diamond tools in rock removal processes

Polycrystalline diamond compacts of relatively coarse grain size were evaluated for their wear properties by cutting a cylindrical core of sandstone on a lathe in a manner designed to produce a helical groove. It was observed that the diamond-diamond grain boundaries are sufficiently strong to sustain the severe stress and abrasion conditions so that each grain acts like a single-crystal diamond cutter and there is no massive particle pull-out. The wear mode is similar to that of a single-crystal diamond, except that gross cleavage is reduced by deformation bands generated during the sintering process.

Some observations on the wear of diamond tools used in piston machining

Abstract The two existing theories which explain the wear mechanism of diamond are reviewed. Brief mention is made of the industrial application of diamond, in particular the use of diamond turning tools for Al/Si piston skirt finishing. The considerable variation in tool life span for this application is noted and the terms of reference for the investigation are stated. The technique and procedure of testing and examination of tools is described. After outlining the extent and position of wear, a more detailed description of various aspects is made, which includes the effect of crystal orientation, incidence of fracture and the possible effect of growth layers. The microstructure of observed wear is dealt with, in which an attempt is made to explain some of the phenomena described. Finally, the opinion is expressed that a critical crystal orientation is unlikely to be economically justifiable but that various avoidable macro defects affect tool life. It is also suggested that the type of wear mechanism might be load-dependent but that the general mechanism, if mechanical, involves submicro fragmentation.