Single Point Diamond Tool Research Articles

Effect of parameters on surface roughness during the ultra-precision polishing of titanium alloy

Titanium alloys have great potential in ultra-precision situations due to the excellent properties, such as high corrosion resistance, high specific-strength and high biocompatibility. However, the application of titanium alloys in ultra-precision field is limited by the poor machinability. There are difficulties in obtaining the optical surface. In this study, the possibility for obtaining optically graded surfaces of titanium alloys by ultra-precision polishing was investigated. Before the ultra-precision polishing, ultra-precision turning with a single point diamond tool was used to get all sample surfaces. But, titanium alloy is difficult to obtain good surface quality by ultra-precision diamond turning. The samples results confirmed that most of the surface roughness values are higher than 30 nm. In order to explore the polishing process, a large number of ultra-precision polishing experiments were conducted. In addition, the effects of different ultra-precision polishing parameters on the surface profiles of titanium alloy Ti6Al4V were investigated in depth. The results show that the average values of surface roughness of titanium alloy parts with ultra-precision turning can be further reduced by 70% or so by ultra-precision polishing. Using a reasonable combination of high spindle speed and large cutting depth, the value of surface roughness can even be lower than 2 nm.

Model of Ploughing Cortical Bone with Single-Point Diamond Tool.

Generating topological microstructures on the surface of cortical bone to establish a suitable microenvironment can guide bone cells to achieve bone repair. Single-point diamond tools (SPDTs) have advantages in efficiency and flexibility to fabricate surface microstructures. However, the cutting force during ploughing cannot be predicted and controlled due to the special properties of cortical bone. In this paper, a novel cutting model for ploughing cortical bone using an SPDT was established, and we comprehensively considered the shear stress anisotropy of the bone material and the proportional relationship between the normal force and the tangential force. Then, the orthogonal cutting experiment was used to verify the model. The results show that the error of calculated value and the experimental data is less than 5%. The proposed model can be used to assist the fabrication of microstructures on cortical bone surface using an SPDT.

An application of the edge reversal method for accurate reconstruction of the three-dimensional profile of a single-point diamond tool obtained by an atomic force microscope

An application of the edge reversal method for accurate reconstruction of the three-dimensional profile of a single-point diamond tool obtained by an atomic force microscope

Load-reduction mechanism of microstructure broach inspired by dung beetle surface

Broaching is extensively used in aerospace industry due to the good dimensional quality and surface integrity condition obtained. However, the coupled workload of heat and cutting forces make broaching tool having the problem of serious wear. Many studies have shown that the use of biomimetic microstructure can reduce the cutting load, but the load reduction mechanism is unclear. In this regard, a novel dry broaching experiment, inspired by the dung beetle surface, was designed to investigate the load reduction mechanism of microstructure broach. To reveal the mechanism, the broaching load, chip reduction coefficient and tool-chip adhesion length were compared with four kinds of rake face microstructures, which is conventional broach (without microstructures), biomimetic one (BM), micro-pit (PM) and micro-groove (GM). And all of above microstructures were fabricated by single point diamond tool (SPDT). It can be found that the biomimetic microstructure (BM) can reduce more tool-chip contact area, meanwhile enhance the ability of capturing debris. Otherwise, the obtained results revealed that biomimetic microstructures (BM) broach could reduce broaching load, chip reduction coefficient and tool-chip adhesion length by amount of 12.31 %, 8.23 % and 18.38 % compared to conventional one, respectively.

Effect of KDP-Crystal Material Properties on Surface Morphology in Ultra-Precision Fly Cutting.

To study the effect of material properties on the surface morphology of potassium dihydrogen phosphate (KDP) crystals, an ultra-precision fly cutting machine tool with a single-point diamond tool was used to perform a cutting experiment on (100) crystal plane of the KDP crystal. The elastic modulus, shear modulus, hardness, and dislocation of KDP crystals are taken into the cutting force model by introducing the strain gradient plasticity theory. Since the size effect and dynamic response will affect the surface roughness during ultra-precision machining, the surface roughness of workpieces in ultra-precision fly cutting is hard to predict. Based on the previously established strain gradient plasticity theoretical model, cutting force model, and the dynamic characteristics of the ultra-precision fly cutting system, a surface morphology prediction model under the influence of KDP crystal material properties was established. Finally, the accuracy of the surface morphology prediction model was verified by ultra-precision fly cutting experiments, and identified the frequency range of the characteristic signal caused by the anisotropy of the KDP crystal from the frequency, thereby verifying the KDP crystal material properties has a significant effect on the surface of the machined workpiece roughness.

High-Precision Cutting Edge Radius Measurement of Single Point Diamond Tools Using an Atomic Force Microscope and a Reverse Cutting Edge Artifact

This paper presents a measurement method for high-precision cutting edge radius of single point diamond tools using an atomic force microscope (AFM) and a reverse cutting edge artifact based on the edge reversal method. Reverse cutting edge artifact is fabricated by indenting a diamond tool into a soft metal workpiece with the bisector of the included angle between the tool’s rake face and clearance face perpendicular to the workpiece surface on a newly designed nanoindentation system. An AFM is applied to measure the topographies of the actual and the reverse diamond tool cutting edges. With the proposed edge reversal method, a cutting edge radius can be accurately evaluated based on two AFM topographies, from which the convolution effect of the AFM tip can be reduced. The accuracy of the measurement of cutting edge radius is significantly influenced by the geometric accuracy of reverse cutting edge artifact in the proposed measurement method. In the nanoindentation system, the system operation is optimized for achieving high-precision control of the indentation depth of reverse cutting edFigurege artifact. The influence of elastic recovery and the AFM cantilever tip radius on the accuracy of cutting edge radius measurement are investigated. Diamond tools with different nose radii are also measured. The reliability and capability of the proposed measurement method for cutting edge radius and the designed nanoindentation system are demonstrated through a series of experiments.

The Influence of Circumferential Waviness of the Diamond Wheel Working Surface on the Machined Surface Roughness

The authors investigate the potential of damping down the undulating change of form of a diamond wheel working surface by dressing it with a single-point diamond tool. This is shown to alter the machined surface roughness parameters, namely: the height parameters decrease, the spacing of the profile irregularities and the parameters of the reference length of the profile grow.

Studying the effects of cutting parameters on burr formation and deformation of hierarchical micro-structures in ultra-precision raster milling

Hierarchical micro-structures are composed of a primary micro-structure and secondary micro V-grooves (SMVGs) cut by the UPRM one-step method. The key problem is the existence of burrs and plastic deformation of the top of SMVGs during the fly cutting process. This paper presents a study of the burr and deformation information introduced by one-step cutting operation in ultra-precision raster milling (UPRM). A series of experiments was carried out to investigate the effect of cutting conditions on the quality of hierarchical micro-structures by the one-step cutting method. A single point diamond tool with a 40° tool angle was employed to perform the one-step cutting operation in UPRM. Hierarchical micro-structures were produced on copper material successfully. Large burrs and plastic deformation were formed when cutting with a fixed tool angle. These large burrs and deformation were found to be induced by cutting force and cutting parameters. It was found that large burrs are formed with an increase of the cutting depth, feed rate, and spindle speed; the plastic deformations become serious with an increase of the cutting depth and feed rate, but are reduced with a decrease of spindle speed. An experimental study was established to investigate cutting force as a function of the cutting conditions in relation to micro-burr formation in machining, and explore the problems associated with one-step fly cutting in UPRM. The mechanisms of burrs and plastic deformation of SMVGs are discussed to further improve the machining process.

Evaluation of Diamond Dressing Effect on Workpiece Surface Roughness by Way of Analysis of Variance

Abstract: Wheel dressing is an important action in the grinding process. This paper reports on the comparative study of the performance of two types of diamond dresser tool measured in terms of ground surface roughness. For experiments were used two types of dressers, single point and multi-point diamond dresser. In addition to the dresser tool, the wheel dressing speed and dressing depth were taken into account as dressing variables. Cutting conditions were a constant; the results of dressing were observed for bearing steel 100Cr6. The experimental study was designed using an orthogonal array and experimental data were processed by the analysis-of-variance method (ANOVA). The results show that with a 95% confidence, dressing with a multi-point diamond tool results in a smoother ground surface than with a single point diamond tool. As expected, wheel dressing speed and dressing depth also have significant effects on surface roughness. However, wheel dressing speed is much more influential than dressing depth.

An ultra-precision tool nanoindentation instrument for replication of single point diamond tool cutting edges

Precision replication of the diamond tool cutting edge is required for non-destructive tool metrology. This paper presents an ultra-precision tool nanoindentation instrument designed and constructed for replication of the cutting edge of a single point diamond tool onto a selected soft metal workpiece by precisely indenting the tool cutting edge into the workpiece surface. The instrument has the ability to control the indentation depth with a nanometric resolution, enabling the replication of tool cutting edges with high precision. The motion of the diamond tool along the indentation direction is controlled by the piezoelectric actuator of a fast tool servo (FTS). An integrated capacitive sensor of the FTS is employed to detect the displacement of the diamond tool. The soft metal workpiece is attached to an aluminum cantilever whose deflection is monitored by another capacitive sensor, referred to as an outside capacitive sensor. The indentation force and depth can be accurately evaluated from the diamond tool displacement, the cantilever deflection and the cantilever spring constant. Experiments were carried out by replicating the cutting edge of a single point diamond tool with a nose radius of 2.0 mm on a copper workpiece surface. The profile of the replicated tool cutting edge was measured using an atomic force microscope (AFM). The effectiveness of the instrument in precision replication of diamond tool cutting edges is well-verified by the experimental results.

Study on quasi-orthogonal machining of elastomer pad by single-point diamond tool

Chemical mechanical polishing (CMP) process has been a popular wafer and thin film planarization process for semiconductor fabrication. In CMP process, a diamond dresser with well-distributed diamond grits is usually applied for regenerating the pad surface topography to maintain the pad polishing capability. This paper describes the fundamentally quasi-orthogonal diamond dressing process by pyramid single-point diamond tools at different grit angles under the fixed down pressure and slow dressing speed for elastomer pad conditioning. Experiments of single-point diamond dressing by both face direction dressing (FDD) and edge direction dressing (EDD) have been performed to investigate the normal force profile and pad surface topography. Experimental results show that FDD generates a higher quality of pad surface with lesser plowing volume and relatively stable pad cutting rate (PCR). Moreover, diamond grit with grit angle of 90° has been found to be most suitable while shifting between EDD and FDD during actual diamond dressing process. Results of this study can be applied to diamond dresserv design and optimization of the pad surface topography uniformity in diamond dressing process for CMP of integrated circuit (IC) production.

An edge reversal method for precision measurement of cutting edge radius of single point diamond tools

A method, which is referred to as the edge reversal method, is proposed for precision measurement of the cutting edge radius of single point diamond tools. An indentation mark of the cutting edge which replicates the cutting edge geometry is firstly made on a soft metal substrate surface. The cutting edge of the diamond tool and its indentation mark, which is regarded as the reversal cutting edge, are then measured by utilizing an atomic force microscopy (AFM), respectively. The cutting edge radius can be accurately evaluated through removing the influence of the AFM probe tip radius, which is comparable to the cutting edge radius, based on the two measured data without characterization of the AFM probe tip radius. The results of measurement experiments and uncertainty analysis are presented to demonstrate the feasibility of the proposed method.

Process modeling study of the ultrasonic elliptical vibration cutting of Inconel 718

As an advanced cutting method, ultrasonic elliptical vibration cutting (UEVC) has been successfully applied to machine difficult-to-cut materials for the last decade. However, few researches have been studied on cutting of Inconel 718 using a single-point diamond tool applying the UEVC method. The objective of this paper was to experimentally derive empirical equations for the prediction of multiple machined surface roughness parameters for UEVC machined Inconel 718 workpiece by means of a systematic statistical experimental approach. A Taguchi parametric screening design of experiments (DOE) was carried out to systematically determine the UEVC process parameters with the largest effect on mean surface roughness. Next, empirically determined equations for the four common surface roughness metrics (Ra, Rq, Rc, and Rz) were developed via Box-Behnken surface response tests. Validation tests were conducted resulting in predicted and experimental surface roughness in varying levels of agreement. The ultrasonic effect on surface quality was also discussed to confirm feasibility of UEVC of Inconel 718 with diamond cutting tools.

Model for cutting force prediction in high precision single-point diamond turning of optical silicon

This paper presents a mathematical model predicated on a finite series convergent scheme and derivative functions of multi-variants obtained from a cutting force constitutive equation for onward prediction of the maximum cutting force at the tip of a single-point diamond tool (SPDT). The three variants amidst other parameters in the model include the tool length, width and strain effect. The model basically operates under two components, namely the dynamic and predictive components. Prior to the predictive analysis, cutting experiments were carried out using an ultra-high precision machine to diamond-turn units of single-crystal silicon workpiece. Results from nine experimental trials are presented. Other supporting devices deployed for signal monitoring and conditioning include the use of a Kistler force sensor, an analog-digital (AD) sensor for data acquisition and an amplifier unit for signals. The cutting parameters adopted for the experimental process includes depth of cut, feed rate and cutting speed. The simulation interval for the investigation of the cutting force was fixed at intervals of 1 mm from the point of sensor insert to the tip of the tool. The dynamical response of the proposed algorithm to each experimental trial, as seen in the displayed results, shows a trend commensurate to the geometry of the diamond-cutting tool and stiffness of the machined material.

Experimental study on the single grit interaction behaviour and brittle–ductile transition of grinding with a diamond micro-grinding tool

This study presents new information on single grit interaction behaviour and its brittle–ductile transition in micro-grinding single crystal silicon using a single grit diamond tool. A model to describe the energy interaction between the cutting behaviour of a single grit and the workpiece in micro-grinding is established based on the single grit geometry model, which was indicated in Fig. 1a, the critical condition of the volume of material removed and the conservation of energy. The tip angle of the single-point diamond tool has been considered. To reveal the material removal mechanism of micro-grinding, a series of scratching experiments, which conducted with a low cutting speed (0.036 to 0.6 m/s), have been performed in this study. The fractures of the micro-grooves machined using single-point diamond tools have been examined by a microscope and a surface profilometer, thus revealing different processing modes (brittle and ductile). The variation curves of the fracture length c have been presented on the condition of different tool tip angles θ (60° and 120°). It is found that the fracture size of grooves machined by a grit with a blunt angle is comparatively larger than that of a grit with a sharp angle for the same scratching parameters. The scratching speed v and penetration depth p0 have a direct effect on the fracture length c, which increases obviously with the rising of v and p0. The critical condition has been investigated based on the experimental results; the blunt grit (with a larger tip angle: θ = 120°) and the sharp grit (with a smaller tip angle: θ = 60°) have different brittle–ductile transitions and different critical cutting depths, which are 334 nm (θ = 60°) and 607 nm (θ = 120°), respectively. The effects of the scratching speed v are investigated. The brittle–ductile transitions of the different scratching speeds have been compared. The relationship between the fracture length c and the volume of material removed in unit time V has been discussed; V is an important measuring constant for the fracture formation and critical ductile cutting condition. This study reveals the mechanism of the single grit interaction in micro-grinding with an ultra-small grinding tool and provides theoretical and experimental validation for ductile micro-grinding of single crystal silicon.

Fabrication of 3D submicron to micro textured surfaces using backside patterned texturing (BPT)

This work presents a novel fabrication method for submicron to micro size textures on flat surfaces using the backside patterned texturing (BPT). The proposed method utilizes the pre-fabricated macro-features on the backside of work material, and thereafter the front side is face turned with a single point diamond tool to generate textured surfaces. Different from existing texturing methods, BPT produces textured surfaces from submicron to micro scale without any external gadgets such as vibration assisted machining or synchronized tool-spindle motion. The miniature feature arises on the diamond turned surface due to the induced residual stresses when the specimen is unleashed from the machine. To demonstrate the efficacy of the method, a series of machining experiments were conducted to fabricate various types of freeform surface textures like water-drop freeform, cylindrical freeform surfaces, etc. The fabrication methodology of different sizes of bumps with precisely controlled surface quality is illustrated. The texture profiles comprising the deformation height from hundreds of nanometer to few micrometers with mirror surface quality were successfully fabricated on the diamond machined surface. The experimental results suggest that the pre-fabricated pattern, workpiece thickness and machining condition play a critical role to determine the final shape and geometry of generated textures.

Investigation of Surface Roughness of Single Point Diamond Turned Germanium Substrate by Coherence Correlation Interferometry and Image Processing

Germanium is a widely used material in the infrared range. Single crystal germanium is used as semiconductor and optical material due to its salient features like high refractive index and proper working in cryogenic conditions. Thus, germanium is an important substrate for infrared lens having many applications in thermal imaging cameras, optical telescopes and miniaturization of infrared optical elements. These applications require optical elements of excellent surface quality and high dimensional accuracy. In addition to fulfil the demands, ultraprecision machine is used to fabricate the optical components. In this work, single crystal germanium (111) mirror is fabricated by using single point diamond tool with, negative rake angle. A large number of experiments are performed to achieve the surface finish of nanometric range. The best and worst combinations of process parameters are found on the basis of surface roughness with the help of coherence correlation interferometry(CCI) measurement and image processing using Canny, Prewitt, Roberts and Sobel edge filters and histogram. These results can be used for fabrication of diffractive optical elements and aspheric lenses of germanium.

A hybrid method for crackless and high-efficiency ultraprecision chamfering of KDP crystal

To enhance the optical performance of the optics used in inertial confinement fusion (ICF), the edges of the large-sized KDP crystal need to be removed to form chamfered faces with high surface quality (RMS <5 nm). Fly cutting with single point diamond tool has been widely used to process potassium dihydrogen phosphate (KDP) to achieve extremely high surface quality. However, the depth of cut (DOC) of fly cutting is usually several microns, which results in very low machining efficiency for the chamfering of KDP crystal as the amount of materials to be removed is in the order of millimeter. To overcome this problem, this paper proposes a hybrid machining method by combining precision grinding with fly cutting to achieve crackless and high-efficiency ultraprecision chamfering of KDP crystal. In addition, a combined machine tool has been developed, and experiments have been carried out to determine the optimal machining procedures and verify the effectiveness of the proposed method. Experimental results show that the machining efficiency can be improved by nearly five times using the proposed method to produce the same machined surface quality as that of the traditional fly cutting process.

A Study on Ultrasonic Elliptical Vibration Cutting of Inconel 718

Inconel 718 is a kind of nickel-based alloys that are widely used in the aerospace and nuclear industry owing to their high temperature mechanical properties. Cutting of Inconel 718 in conventional cutting (CC) is a big challenge in modern industry. Few researches have been studied on cutting of Inconel 718 using single point diamond tool applying the UEVC method. This paper shows an experimental study on UEVC of Inconel 718 by using polycrystalline diamond (PCD) coated tools. Firstly, cutting tests have been carried out to study the effect of machining parameters in the UEVC in terms of surface finish and flank wear during machining of Inconel 718. The tests have clearly shown that the PCD coated tools in cutting of Inconel 718 by the UEVC have better performance at 0.1 mm depth of cut as compared to the lower 0.05 mm depth of cut and the higher 0.12 or 0.15 mm depth of cut. Secondly, like CC method, the cutting performance in UEVC increases with the decrease of the feed rate and cutting speed. The CC tests have also been carried out to compare performance of CC with UEVC method.

Novel corrective machining method to fine-tune groove widths

Using lenticular lenses to realize auto-stereoscopic displays has become increasingly popular in the TV industry, especially in the area of developing multi-view glasses-free 3D TV. Each lenticular lens has many sublenses through which the light is diverted in different directions. A multi-view TV display projects a vertically rotated 3D image to a viewer that seamlessly matches his or her sideways movement. To do so, it poses a very stringent requirement on machining lenticular lens mold. Using a tailor-made cutting tool, the profile of the lenticular grooves can be machined very precisely, and in a very efficient manner; however, the groove width might vary due to elastic bouncing. Such variation of the groove width leads to disparity in the light intensity entering the left and right eye of the viewer. The 3D perception would then unavoidably deteriorate. Thus, a corrective machining method must be developed to fine-tune the groove width. In this paper, a method involving transverse cutting perpendicular to the axes of the lenticular grooves is proposed, in which the cutting is done transversely across the grooves using a single point diamond tool. The depth of corrective cut is 1 μm, and the errors in the groove widths can be corrected to ±200 nm.