A comprehensive analysis of literature pertaining to surface texture metrology for metal additive manufacturing has been performed. This review paper structures the results of this analysis into sections that address specific areas of interest: industrial domain; additive manufacturing processes and materials; types of surface investigated; surface measurement technology and surface texture characterisation. Each section reports on how frequently specific techniques, processes or materials have been utilised and discusses how and why they are employed. Based on these results, possible optimisation of methods and reporting is suggested and the areas that may have significant potential for future research are highlighted.
Vibration-assisted machining (VAM) combines precision machining with small-amplitude tool vibration to improve the fabrication process. It has been applied to a number of processes from turning to drilling to grinding . The emphasis on this literature review is the turning process where VAM has been applied to difficult applications such as diamond turning of ferrous and brittle materials, creating microstructures with complex geometries for products like molds and optical elements, or economically producing precision macro-scale components in hard alloys such as Inconel or titanium. This review paper presents the basic kinematic relationships for 1D (linear vibratory tool path) and 2D VAM (circular/elliptical tool path). Typical hardware systems used to achieve these vibratory motions are described. The periodic separation between the tool rake face and uncut material, characteristic of VAM, is related to observed reductions in machining forces and chip thickness, with distinct explanations offered for 1D and 2D modes. The reduced tool forces in turn are related to improvements in surface finish and extended tool life. Additional consideration is given to the intermittent cutting mechanism and how it reduces the effect of thermo-chemical mechanisms believed responsible for rapid wear of diamond tools when machining ferrous materials. The ability of VAM to machine brittle materials in the ductile regime at increased depth of cut is also described.
In this paper, a method for the minimization of cutting forces and vibrations during precise ball end milling of hardened 55NiCrMoV6 steel is developed. The aim of this work concentrates on the optimal selection of surface inclination angle α and tool’s overhang , which enables the minimization of cutting forces and vibrations in order to improve the machined surface quality. The experiment includes the measurement of cutting forces and acceleration of vibrations during the milling tests with variable input parameters. The next step focuses on the optimization of the ball end milling process with the consideration of the acquired signals. This procedure is carried out by the minimization of process responses with the application of signal to noise S/N ratio and grey relational analysis (GRA). Subsequently, the obtained optimal values of process input parameters are validated during the ball end milling tests involving the measurements of machined surface topographies. Research reveals that surface inclination angle and tool’s overhang have significant influence on generated forces and vibration values. Moreover, the selection of the optimal values of α and enables significant improvement of machined surface quality.
Wire sawing technology has been widely adopted for slicing of brittle-and-hard materials including crystalline silicon, SiC and sapphire. This paper presents a literature review on the research efforts on wire sawing related topics. First, the system and process level investigations of wire sawing technology, including both multi-wire slurry sawing and diamond wire sawing, are summarized. Ingot materials used in wire sawing technology, as well as their properties and behavior during sawing operation are discussed. As modeling and analysis of single grit indentation and scribing of brittle materials provide fundamental insight on material removal and these can be leveraged for wire sawing analysis at system level, a review of those models and modified models proposed particularly for wire sawing process are also presented. After the survey of current state-of-the-art, this contribution proposes important research aspects to be further worked on to gain more complete scientific understanding of wire sawing technology.
We developed novel cutting tools that had either microscale or nanoscale textures on their surfaces. Texturing microscale or nanoscale features on a solid surface allowed us to control the tribological characteristics of the tool. The textures, which had pitches and depths ranging from several hundreds of nanometers to several tens of micrometers, were fabricated utilizing the ablation and interference phenomena of a femtosecond laser. The effect of the texture shape on the machinability of an aluminum alloy was investigated with a turning experiment applying the minimum quantity lubrication method. The texture decreased the cutting force due to the corresponding reduction in the friction on the rake face. This effect strongly depended on the direction of the texture; lower cutting forces were achieved when the texture was perpendicular to the chip flow direction rather than parallel. This effect was only observed at high cutting speeds over 420 m/min. These results indicate that the developed tools effectively improved the machinability of the alloy.
► An innovative process is proposed for the fast generation of structured surfaces. ► The new process utilizes controlled elliptical vibrations of the cutting tool. ► The piezo transducer delivers an elliptical trajectory at an ultrasonic frequency. ► The device has two coupled vibration modes at nearly the same frequency. ► Micro dimple arrays have been created by the developed device. The elliptical vibration texturing process is an innovative machining method for the fast generation of textured surfaces. It adds a tertiary motion component to the tool tip, which introduces deliberate elliptical vibrations between the cutting tool and the workpiece. The elliptical locus lies in the plane that is defined by the cutting direction and the radial direction in the turning operation. This paper proposes a new design for a resonant mode 2D tertiary motion generator (TMG) that can deliver the required elliptical trajectory at an ultrasonic frequency. The device works in the resonant mode, with tangential and normal vibrations at a nearly identical resonant frequency. Simulation and experiments were carried out to perform a modal analysis of the system. Different design parameters were adjusted to achieve large vibration amplitudes in both tangential and normal directions. The elliptical vibration texturing process was implemented by integrating the newly developed TMG into a turning operation. Preliminary test results of dimple array patterns are presented that validate the performance and principle of the proposed design.
A finite element (FE) model was established for high-speed grinding of particulate reinforced titanium matrix composites (PTMCs). The materials removal mechanism, including the grinding force and resultant stress, the removal behavior of alloy matrix and reinforcing particles, have been analyzed. Particularly, the effect of grinding parameters on the surface defects was discussed. The results indicate that, the grinding force has different characteristics when the alloy matrix and reinforcing particle were removed, respectively, and the grinding force fluctuates significantly in the removal process of reinforcing particle. The material removal can be divided into four stages: plastic removal of the alloy matrix, crack initiation in reinforced particles, crack propagation in reinforced particles, brittle failure of reinforced particles. Under the current grinding conditions, compared with the grinding speed, the undeformed chip thickness has greater influence on the formation of machined surface defects. The simulation results agreed well with experiment.
We have proposed cutting tools with various textured surfaces to increase cutting tool life. Our previous studies have developed cutting tools having periodical stripe-grooved surfaces on their rake face formed using femtosecond laser technology, which displayed high crater wear resistance in cutting of steel materials. In this study, the mechanism for suppressing the crater wear on the tool surface and the relationship between texture dimensions and wear resistance were investigated to provide a guideline for developing tools with textured surfaces. Furthermore, we newly introduced the textured surfaces into a flank face of cutting tools to improve flank wear resistance. Face milling experiments on steel materials exhibited that the newly developed tool having the textured flank face significantly reduced the flank wear. Moreover, the influences of texture dimensions and cutting conditions on the flank wear resistance were also discussed.
In this paper we introduce a new design principle, and complementary geometric entities, that form the basis for a new approach to the synthesis of multi-degree of freedom, purely parallel precision flexure systems. This approach – Freedom and Constraint Topology (FACT) – is unique in that it is based upon sets of geometric entities that contain quantitative information about a flexure system's characteristics. A first set contains information about a flexure system's degrees of freedom (its freedom topology) and a second set contains information about the flexure system's topology (its constraint topology). These sets may be used to visualize the quantitative relationships between all possible flexure designs and all possible motions for a given design problem. We introduce a new principle – complementary topologies – that enables the unique mapping of freedom and constraint spaces. This mapping makes it possible to visualize and determine the general shape(s) that a viable parallel flexure system concept must have in order to permit specified motions. The shapes contain all of the relevant quantitative information that is needed to rapidly sketch early embodiments of complex parallel flexure system concepts. These shapes may then be used to rapidly synthesize a multiplicity of flexure system concepts that have (a) independent rotational and/or linear motions, (b) coupled linear and rotational motions, and (c) redundant constraints that permit the desired motions while improving stiffness, load capacity and thermal stability. This enables early-stage flexure system design via “paper and pencil sketches” without undue complications that arise when one focuses upon detailed mathematical treatments that are better-suited for optimization rather than visualization and synthesis.
Thirty years since their invention, laser trackers are now recognized as the measurement tool of choice in the manufacture and assembly of large components. The general design of laser trackers, i.e., a ranging unit on a two-axis gimbal, has not changed significantly over the years. However, innovations in ranging technology, for example, the emergence of increasingly accurate absolute distance meters (ADMs), are providing users with an alternative to interferometers (IFMs). Hand-held accessories such as touch probes and line scanners are expanding the scope and applicability of laser trackers. In this paper, we survey the literature in all areas of laser trackers as applied to large-scale dimensional metrology (LSDM), with emphasis on error modeling, measurement uncertainty, performance evaluation and standardization.
The market for freeform and high quality microdies and moulds made of steel is predicted to experience a phenomenal growth in line with the demand for microsystems. However, micromachining of hardened steel is a challenge due to unpredictable tool life and likely differences in process mechanism compared to macro-scale machining. This paper presents an investigation of the size effect in micromilling of H13 hardened tool steel. In this case, the size effect in micromilling hardened tool steel was observed by studying the effect of the ratio of undeformed chip thickness to the cutting edge radius on process performance. The paper explores how this ratio drives the specific cutting force, surface finish and burr formation in micro-scale machining. In addition, the effect of different microend mill geometry on product quality was explored. The paper provides a valuable insight into optimum micro-scale machining conditions for obtaining the best surface finish and minimizing burr size.
This paper presents a multi-axis surface encoder that can measure six-degree-of-freedom (six-DOF) translational displacement motions and angular motions of a planar motion stage. The six-DOF surface encoder is composed of a planar scale grating and an optical sensor head. A blue laser diode with a wavelength of 405 nm and an output power of 25 mW was employed as the light source of the sensor head. The light rays from the laser diode were collimated to a parallel beam with a diameter of 1.8 mm. The collimated beam was divided by a beam splitter into two beams, which were projected onto the scale grating and a reference grating with an identical grating period of 0.57 μm, respectively. The three-DOF translational displacement motions of the scale grating with respect to the sensor head along the -, - and -directions were detected from the interference signals generated by superimposition of the first-order diffraction beams from the two gratings. A part of the zeroth-order and the negative first-order diffraction beams from the scale grating were employed for detection of the three-DOF angular motions about the -, - and -axes. The sensor head was designed to have a dimension of 95 mm ( ) × 90 mm ( ) × 25 mm ( ) so that it can be mounted on a previously developed planar motion stage. The grating area of the scale grating was designed to be 60 mm ( ) × 60 mm ( ), which was larger than the stage moving ranges of 40 mm ( ) × 40 mm ( ). Experiments were carried out to test the basic performances of the surface encoder.
This article presents the comparison of various compliance/stiffness equations of circular flexure hinges with FEA results. The limitation of these equations at different ( is the radius and is the neck thickness) ratios are revealed. Based on the limitations of these design equations, a guideline for selecting the most accurate equations for hinge design calculations are presented. In addition to the review and comparisons, general empirical stiffness equations in the - and -direction were formulated in this study (with errors less than 3% when compared to FEA results) for a wide range of ratios ( ).
A novel 6D measurement system was recently proposed, comprising a single commercially available telescoping ballbar and two custom-made fixtures. One fixture is attached to the robot base and the other to the robot end-effector, and each having three magnetic cups. In each of 72 poses of the tool fixture, with respect to the base fixture, it is possible to measure six distances with the ballbar between the magnetic cups on the tool fixture and the magnetic cups on the base fixture, and thus calculate the pose with high accuracy. This paper is the first to present the successful use of this measurement system for absolute robot calibration. The robot calibrated is a Fanuc LR Mate 200iC six-axis industrial robot and the telescoping bar used is the QC20-W by Renishaw. The absolute position accuracy of the robot after calibration is validated with a Faro laser tracker in almost 10,000 robot configurations. Considering the validation data in only the front/up configurations, the mean absolute positioning error is improved from 0.873 mm to 0.479 mm. To allow a comparison, the robot is also calibrated using the laser tracker and the robot accuracy validated in the same 10,000 robot configurations.
In this work a new approach to surface roughness parameters estimation during finish cylindrical end milling is presented. The proposed model includes the influence of cutting parameters, the tool’s static run out and dynamic phenomena related to instantaneous tool deflections. The modeling procedure consists of two parts. In the first stage, tool working part instantaneous displacements are estimated using an analytical model which considers tool dynamic deflections and static errors of the machine – tool-holder – tool system. The obtained height of the tool’s displacement envelope is then applied in the second stage to the calculation of surface roughness parameters. These calculations assume that in the cylindrical milling process, two different mechanisms of surface profile formation exist. Which mechanism is present is dependent on the feed per tooth and the maximum height of the tool’s displacement envelope. The developed model is validated during cylindrical milling of hardened hot-work tool steel 55NiCrMoV6 using a stylus profiler and scanning laser vibrometer over a range of cutting parameters. The surface roughness values predicted by the developed model are in good agreement with measured values. It is found that the employment of a model which includes only the effect of static displacements gives an inferior estimation of surface roughness compared to the model incorporating dynamic tool deflections.
The present work pertains to the analysis of surface topography of explosively clad material such as titanium plated steel in drilling process. The study was conducted for different types of indexable insert drills with different configuration of the tool coatings and for WC-Co drill tool. In this context, surface topography of the drilled holes especially in the region of contact area was analyzed. Metrological analysis was performed using stylus-based and optical profilometry. In this paper the differences between mechanically and electromagnetically measured surfaces are highlighted. It has been observed that the parameters of the surface topography are dependent upon the type of layers of the clad and the type of drill.
Recently, surface texturing has received much attention as a method of enhancing the tribological properties of a cutting tool surface. However, effective texture patterns and dimensions on a tool surface are still difficult to obtain and suitable textures can be obtained only by trial and error. In order to overcome this problem, we newly develop cutting tools with dimple-shaped textures having different dimensions and arrays, generated on the tool rake face. In addition, we evaluate their crater wear resistance and cutting forces in steel material cutting. Furthermore, under various cutting conditions, the performances of the cutting tools with dimple-shaped textures are compared with those of tools with groove-shaped textures in order to establish a guideline for designing appropriate surface textures on cutting tool surfaces. A series of cutting experiments demonstrate that the dimple textures significantly improve the crater wear resistance and the tribological behavior on the tool rake face, and they exhibit a superior performance compared with those with groove textures, especially in a severely lubricated environment.
In this study, both finite element analysis (FEA) and experimental observations were used to investigate the single CBN grain wear in high-speed grinding of Inconel 718 superalloy. The wear characteristics for each grinding pass were numerically assessed utilizing the tensile and compressive strength limits of the cutting grain. Additionally, stress distribution within the grain, chip formation and grinding force evolution during multiple passes were investigated. The combined experimental and numerical results show that the CBN grain wear has two major modes: the macro fracture on the grain top surface propagating from the rake surface, and the micro fracture near the cutting edges. The resultant tensile stress is the main factor inducing grain wear. The cutting edges will be under self-sharpening due to the grain wear. With multiple micro cutting edges engaged in grinding process, the limited material removal region was divided into different sliding, ploughing and cutting dominant regions. Overall, the ratio of material elements removed by a cutting process ranges from 80% to 20%, and continue to decrease during the grinding process. With a stronger effect of the cutting process, larger fluctuation of the grinding force will commence, however its average value remains below that with stronger sliding and ploughing process characteristics.
There is a growing interest in the machining of micro-holes with high aspect-ratio in difficult-to-machine alloys for the aerospace industry. Processes based on electro discharge machining (EDM) and developed for the manufacture of both micro-electrode and micro-hole are actually used, but most of them involve micro-EDM machines. In this work, the influence of EDM parameters on material removal rate, electrode wear, machining time and micro-hole quality when machining Ti6Al4V is studied. Due to an inefficient removal of debris when increasing hole depth, a new strategy based on the use of helical-shaped electrodes has been proposed. The influence of helix angle and flute depth with respect to process performance has been addressed. Main results include 37% reduction in machining times (hole diameter 800 μm) when using electrode helix angle of 45° and flute-depth of 50 μm, and an additional 19% with flute-depth of 150 μm. Holes of 661 μm diameter and as much as 6.81 mm depth, which yields in aspect ratio of 10:1, have successfully been machined in Ti6Al4V.
Accurate simulation of the machining process is crucial to improve milling performance, especially in High-Speed Milling, where cutting parameters are pushed to the limit. Various milling critical issues can be analyzed based on accurate prediction of cutting forces, such as chatter stability, dimensional error and surface finish. Cutting force models are based on coefficients that could change with spindle speed. The evaluation of these specific coefficients at higher speed is challenging due to the frequency bandwidth of commercial force sensors. On account of this, coefficients are generally evaluated at low speed and then employed in models for different spindle speeds, possibly reducing accuracy of results. In this paper a deep investigation of cutting force coefficient at different spindle speeds has been carried out, analyzing a wide range of spindle speeds: to overcome transducer dynamics issues, dynamometer signals have been compensated thanks to an improved technique based on Kalman filter estimator. Two different coefficients identification methods have been implemented: the traditional average force method and a proposed instantaneous method based on genetic algorithm and capable of estimating cutting coefficients and tool run-out at the same time. Results show that instantaneous method is more accurate and efficient compared to the average one. On the other hand, the average method does not require compensation since it is based on average signals. Furthermore a significant change of coefficients over spindle speed is highlighted, suggesting that speed-varying coefficient should be useful to improve reliability of simulated forces.