Finish Machining Research Articles

Optimization of parameters in cylindrical and surface grinding for improved surface finish.

Surface integrity has attracted the attention of researchers for improving the functional performance of engineering products. Improvement in surface finish, one of the important parameters in surface integrity, has been attempted by researchers through different processes. Grinding has been widely used for final machining of components requiring smooth surfaces coupled with precise tolerances. Proper selection of grinding wheel material and grade with grinding parameters can result in an improved surface finish and improved surface characteristics. The present work reports the study of the effect of grinding parameters on surface finish of EN8 steel. Experiments were performed on surface grinding and cylindrical grinding for optimization of grinding process parameters for improved surface finish. Grinding wheel speed, depth of cut, table feed, grinding wheel material and table travel speed for surface grinding operation, and work speed for cylindrical grinding operation were taken as the input parameters with four types of grinding wheels (Al2O3 of grades K and L, and white alumina of grades J and K). The surface roughness was taken as an output parameter for experimentation. The grinding wheel material and grade have been observed to be the most significant variables for both cylindrical grinding and surface grinding. Surface roughness in the case of surface grinding is better compared to that of cylindrical grinding, which can be attributed to vibrations produced in the cylindrical grinding attachment. Surface roughness (Ra) values of 0.757 µm in cylindrical grinding and 0.66 µm in surface grinding have been achieved.

Surface motion analysis of double vibro-polishing of Ti-6Al-4 V

Fixturing of workpieces is commonly deployed in vibratory finishing due to the various benefits that this immobilization technique has to offer. The most significant of the benefits is the quality surface finish that can be achieved in shorter process times. Vibratory fixturing is a method where the component is clamped onto a vibrator to induce vibrations to the workpiece. This can accelerate cycle times when incorporated on a vibratory finishing machine. In this work, experiments were conducted using machine and vibratory fixture as the factors influencing the time taken to reach its required average surface roughness of 1 μm. A novel combination of high-speed camera videos and motion analysis software was used to assess the media impact velocities at the media circulating in the machine and thus to elucidate the results obtained in the experimental investigations.

Electrochemical Surface Finishing of Additively Manufactured Parts

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in Fig. 1, are natural candidates for AM. With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in Fig. 2. With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management). The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining. Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable a wide range of complex components to be finished, deburred, radiused, or polished. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology of various material groups including but not limited to titanium alloys, tantalum alloys, nickel alloys, stainless steels, niobium, and molybdenum alloys. In particular, this talk will discuss techniques in electrofinishing AM / HIPped parts and the design of tooling that enables complex components / passages to be finished to meet the required specifications. Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged. Figure 1

Status of ENEA's Procurement of 9 TF Coils of JT-60SA Tokamak

In the framework of the Broader Approach program for the early realization of fusion with the construction of JT-60SA tokamak, ENEA has to provide nine of the 18 TF coils of the JT-60SA magnet system. The scope of the supply foresees both the manufacturing of the winding packs (WP) and their integration into the casing structure. At the end of 2015, all nine WP were completed and tested. Integration activity started in mid-2015 and it is now almost finished. At present, all nine WP have been inserted in their respective casing structure, while embedding impregnation and final machining have also been concluded. Eight coils have been already tested in cryogenic conditions, and five coils have been assembled in the tokamak. This paper provides an overview of the contract that ENEA signed with ASG Superconductors for this supply. Specifically after an introduction of the contract activity, production performances are reviewed with respect to each manufacturing step. The role of welding activity is particularly emphasized. Also, the results of some electrical, geometrical, and hydraulic tests of the TFC completed so far are reported in order to give a general assessment of the homogeneity of the coils' production and of their performances.

Investigation on the characteristic of forces of the tool edge in finish machining of titanium alloys

In order to tackle the problems during processing titanium alloys, 2D orthogonal cutting mechanics models are proposed in this paper. In particular, models are based on the classical orthogonal force model with the consideration of the blunt tool edge and the chamfering tool edge when the force is less than the tool edge radius. Moreover, simulations and experiments have been carried out to investigate the characteristic of forces of the tool edge. The model describes the relationship between the tool edge and forces. In addition, it can accurately predict the initial flow of the chip under the action of the tool edge. Substantially, the theoretical basis for optimizing the design of the tool edge can be provided.

Vibratory finishing co-simulation based on ADAMS-EDEM with experimental validation

Vibratory finishing has been widely used for surface finishing, cleaning, deburring, deflashing, and stress relief in industry for the past 60 years. In vibratory finishing, the motion behaviors of granular media, determined by a vibratory excitation system, dictate the material removal from and surface quality of workpieces. In this study, a dynamic bowl-type vibratory finishing machine model was developed using ADAMS software. The behavior of the granular media in the vibrating flow field was simulated and analyzed using the EDEM software. The add-in EALink was used to transmit data between ADAMS and EDEM. For model verification, the vibration amplitudes of a container were experimentally measured using acceleration sensors. The contact force of the granular media acting on the workpieces and the velocities of the granular media and workpieces were obtained through co-simulation. Co-simulation can be used to estimate the uniformity of processed workpieces. Finishing experiments were conducted for comparison with co-simulation results using workpieces fixed to the inner wall of the container.

Study on the evolution of residual stress in successive machining process

Residual stress in the machined surface can significantly influence the performance of machined parts. The influence of machining parameters and tool parameters on machining-induced residual stress has drawn much research interests, yet the distribution of initial stress is also an important factor that decides the final residual stress distribution, and there is a complicated evolution process of inner stress field during machining. In this paper, an experimental research was carefully designed and performed, with the help of FEM analysis, to study the evolution process of residual stress field during successive machining. Machining process can cause much more severe influence on the stress field than pure material removal process without external loads. The surface residual stress is mainly decided by the final machining process, while the in-depth residual stress distribution depends on the machining history. Machining process introduces non-uniform plastic deformation. When the Natural Plastic Influencing Range of certain cutting process is much smaller than the existing range of initial stress, this cutting process would either enlarge or reduce the amplitude of the stress distribution, depending on the nature of the initial stress field and the cutting loads, yet it would not significantly influence the existing range of the initial residual stress.

Nanofinishing of 3D surfaces by automated five-axis CNC ball end magnetorheological finishing machine using customized controller

Ball end magnetorheological finishing (BEMRF) is a novel method for nanofinishing of ferromagnetic as well as nonmagnetic materials. With increasing demands of precision finished products in various markets, the quality of surface finish and production rate are of prime importance. For products having complex geometries, this need intensifies as the manual finishing methods are incapable of producing uniform finish throughout the complex geometry of the surface. This paper describes the finishing of 3D surfaces using five-axis CNC BEMRF process in a fully automated manner such that a uniform finish is obtained throughout the workpiece. This eliminates the labor-intensive efforts and the subjective errors involved in manual finishing operations and increases the production rate of the finished products. A customized five-axis CNC controller is developed that enables the sequential and precise control of motion as well as process parameters in the BEMRF machine. The magnetizing current which governs the forces responsible for finishing in BEMRF process is controlled in-process through CNC part program using a specially defined “E” code for magnetizing current. A dedicated graphical user interface is also developed in Visual C# for the control of BEMRF process, enabling the user to make use of BEMRF machine without going into the complexities of the system. Using the customized five-axis CNC controller, automated finishing of a freeform mild steel workpiece is done. The finishing results obtained by the automated five-axis BEMRF machine shows uniformly finished surface profile (up to order of nanometer) on the mild steel test specimen.

Experimental study of chemical mechanical polishing of the final surfaces of cemented carbide inserts for effective cutting austenitic stainless steel

Defects of the final surfaces of cemented carbide inserts by means of conventional grinding method include grinding burn, crack, and thermal deformation, causing low cutting efficiency. To address the problems of the conventional way in grinding the insert surfaces, the chemical mechanical polishing (CMP) process is adopted in finish machining rake faces. First, the CMP process parameters are optimized with orthogonal experiments and Taguchi’s method, and the cemented carbide insert surfaces are made with 14.399 nm Ra of its rake face. Second, the inserts made with the conventional grinding and the CMP methods are used to lathe 1Cr18Ni9Ti austenitic stainless steel. Under the same cutting conditions, the cutting forces of the polished insert is less than those of the grinding insert, the cutting time of the polished insert is longer than that of the grinding insert, and the average life of the polished insert is 32.3% longer than that of the grinding insert. Finally, the scanning electron microscopy (SEM) and the energy dispersive spectroscopy (EDS) analysis have shown that the polished insert rake face has less adhesive wear , abrasive wear, and minor oxidation wear compared to the wear of the grinding insert rake face. This study demonstrates that the CMP is a potential way of processing the insert surfaces in the tooling industry.

Influence of manufacturing processes on material characterization with the grooved in-plane torsion test

In-plane torsion tests offer advantages such as a proportional loading path and a homogeneous stress and strain distribution when characterizing the material behavior in the state of in-plane shear. The use of a grooved specimen is mandatory for the characterization of the damage behavior. The manufacturing of the groove by turning, milling, and electrical discharge machining for a DP600, DP1000, and CP1000 showed a strong influence on the experimentally measurable strain values at failure. Fine machining by milling displayed good results for all tested materials. The notch-effect in turned grooves led to an early fracture initiation. A straightforward parameter identification scheme for the Hosford–Coulomb fracture criterion as proposed by [16] was used to show the sensitivity of fracture curves on the experimental database.

A Review on Sensors for Real-time Monitoring and Control Systems on Machining and Surface Finishing Processes

One of the key components in real-time monitoring and control on machining and surface finishing processes are sensors. The advances of such system have triggered interesting questions on sensor selection that act as the fundamental before starting a project. This paper is made to review and answer the questions surrounding sensor selection. The paper first explains on the type of sensors commonly used in practice for real-time monitoring and control systems. After which, the paper discusses on how often the sensors are used on several machining and surface finishing processes and what are the reasons for the sensor selection. Thereafter, a review on the type features commonly analysed through these sensors is discussed. The paper expects reader would decide better upon selecting sensors and has a better direction in their project. Thus the paper works to guide reader to improve based on what has been completed before.

Some Effects on EDM Characteristics by Assisted Ultrasonic Vibration of the Tool Electrode

It is well known that electrical discharge machining (EDM) is a machining method that does not affect the hardness of the material being processed. The EDM method is widely used for the finish machining of metal molds, for which materials having a high degree of hardness is used. However, the EDM method has a disadvantage in that the machining speed is remarkably slow compared to other machining methods. However, if the discharge energy is increased, the quality of surface finish is decreased. For this reason, it is difficult to machine a finished surface. In order to improve machining characteristics while using the same discharge energy, it is important to homogeneously disperse the discharge, so as to increase the rate of normal discharge, and to discharge the machining dust that accumulates between the electrode and workpiece. However, it is difficult to generate a constantly normal discharge in EDM. What is worse, the more deeply a hole is machined, the more difficult it is to remove the machining dust that accumulates between the electrode and the workpiece. A concentrated discharge tends to occur locally because of the presence of machining dust between the electrode and workpiece. This concentrated discharge has an adverse effect on the surface finish. Also, it creates a big problem, namely a bridging contact is generated between parts. In order to avoid generating such a concentrated discharge or abnormal discharge, it is necessary to disperse the discharge appropriately. In this study, we investigate EDM characteristics by using assisted ultrasonic vibration of the tool electrode as a method of overcoming the problem. The result showed that the machining speed was increased several times by using assisted ultrasonic vibration of the tool electrode. The method proved to remarkably effective in increasing machining speed even if the amplitude of the ultrasonic vibration was 1μm. Furthermore, the rate of normal discharge increased by applying ultrasonic vibration. In particular, this method yielded a beneficial effect in finishing conditions. This is expected to produce a better effect under conditions of finish machining when there is a small gap between the electrode and workpiece. In particular, occurrences of abnormal discharges, such as a concentrated discharge, decreased since the electrode tool was forcibly separated from the workpiece. Machining wastes are positively removed as a result of the tool electrode working with a “pumping action.” In particular, when applied to deep-hole machining, this method is extremely effective in machining deeper holes.

Finish machining-induced surface roughness, microhardness and XRD analysis of selective laser melted Inconel 718 alloy

Selective laser melting (SLM) is one of the most commonly used additive manufacturing (AM) techniques to manufacture metal components; however, during building process partially melted powders and/or pores on the outer surface of metallic parts results in very high surface roughness and eventually poor surface quality of components manufactured by selective laser melting. Thus, post-processing is needed to improve surface quality and also control subsurface characteristics. Hence, this study presents the effects of finish machining process on surface integrity characteristics including surface roughness, microhardness and XRD analysis of selective laser melted (SLMed) Inconel 718 alloy. In machining process of SLMed Inconel 718 alloy, the effect feed rate on measured outputs was also examined. Besides, the role of cold air on surface integrity characteristics was also presented in this study. This study reveals that arithmetic average surface roughness of as-built SLMed Inconel 718 can be lowered more than 90% with finish machining post processing operation. Increased feed rate results in work hardening on the surface and subsurface and eventually microhardness of surface and subsurface increases notably as compared to as-built SLMed Inconel. Finish machining process deeply influences XRD patterns of SLMed Inconel 718 alloy.

射出成形機の型締力変化からの運転モードの推定（生産中の射出成形機から取得したビッグデータの活用）

This article suggests the machine operation mode can be estimated from sensors attached to the machine in the production line. An injection molding machine (IMM), which is widely operated in the plastics industry, was used in this research within an actual production line. Four strain sensors were attached to the IMM to measure the clamping force in each production cycle. Auto or semi-auto mode was estimated from the clamping force sequence. Auto mode is continuous production by the machine itself, while semi-auto mode involves intermittent human operation and includes such functions as machine start, machine finish, and trouble shooting. Approximately 340000 cycle data were obtained in 10-week production. The changing value was calculated by the binomial filter statistical technique, as well as the differencing of time series data from the clamping force in each cycle. And the relationship between changing value and operation mode is evaluated by the area under the curve (AUC) calculated from the receiver operating characteristic curve (ROC curve). As a result, we obtained that AUC value was 0.86 from 10-week production data, which means operation mode can be estimated from the changing value of clamping force in a high level. This estimating method has a low computational cost; therefore it is easy to install on a machine's board control system. We expect that this method will be used to detect the defective product, the machine malfunction or the mold failure.

Predictive Modelling of Surface Roughness for Double Vibropolishing in Trough System

Vibratory finishing is a ubiquitous surface finishing process administered to components of various functionalities. Alongside the development of more complex finishing techniques such as drag finishing and abrasive flow machining, significant progress on numerical simulation has also been achieved, e.g. computational fluid dynamics, discrete element method. Yet, search into predictive roughness modelling has been insipid. In this study, multi-variable regression and artificial neural network modelling was done using experimental data obtained from subjecting rectangular test coupons to double vibropolishing in a vibratory trough. Two regression models, i.e. exponential and power, and several Multi-Layer Perceptron (MLP) architectures were trained using experimental data, and were subsequently evaluated for generalization ability. Model selection was done by comparing the mean-absolute percentage error and r-squared values from both training and testing datasets.

Bending deformation analysis of gear hone tooth lateral faces

Gear hones are used for finish machining of hardened gear tooth lateral faces by the generating method. In service, due to penetration of abrasive grains into metal, wear and running-in of the tool material, especially in the case of elastic binding agents, the tooth contact takes place not in a point, but in an ellipse area. The total bending deformation of a hone tooth in the contact point is a sum of the fixed tooth bending deformation and the deformation, characterizing the tooth root travel in a hone rim. The calculations make it evident that hone tooth bending deformation value depends on the contact point vertical position; it drops by a factor of 400 – 500 from the lower contact point to the top. Besides, deformation increases by a factor of 60 with decrease of the elasticity modulus. The rim part adjacent to a tooth is also considered during analysis of the second component of the total tooth bending deformation, characterizing the tooth root elastic strain. With the tooth height increase, this deformation value increases by a factor of 4 – 20 and significantly (by an order of magnitude) increases with the elasticity modulus drop. Bending deformation analysis results of gear hone teeth are applied for studying their operation capabilities, as well as development of geometry and compound specifications.

傾斜切削法による高硬度材の仕上切削加工

傾斜切削法による高硬度材の仕上切削加工

Influence of different input parameters on the contact conditions determing the surface integrity of workpieces in an unguided vibratory finishing process

The contact force and the relativevelocitybetween workpiece and abrasive media in a vibratory finishing have a strong effect on the material removal rate and the surface roughness of the machined workpieces. Both, the contact force as well as the relative velocity, are mainly influenced by the characteristics of the abrasive media type used as well as the geometry and the density of the workpieces. Furthermore, major influence factors on the contact conditions between the workpiece and abrasive media are the input parameters of the vibratory finishing machine, e.g. the mass distribution between the upper and the lower imbalance weights, the offset angle between the imbalance weights and the rotational speed. In order to determine the influence of the abrasive media and the workpiece characteristics as well as the different input parameters of the machine on the contact conditions, two measurement systems in the form of a camera-integrated workpiece and a workpiece with an integrated piezoelectric sensor have been used. The completely wireless construction of the measurement systems enabled the measurement of the contact force as well as the relative velocity without the influence of wires for data transfers and electrical power supply. The results have shown that the contact force as well as the relative velocityand therefore the surface integrity of the machined workpieces are mainly effected by the adjustments of the rotational speed and the size of the abrasive media.

3D representation and CNC machining of 2D digital images

In this paper a new paradigm for CNC carving of digital images in the form of lookalike three-dimensional (3D) surfaces on wooden or metallic plaques is discussed. This work is focused on development of a single page windows based console application for conversion of a two-dimensional (2D) digital image into a 3D freeform surface representation in the form of a point cloud data and STL format. Subsequently, the 3D surface data is then used for generating an efficient toolpath data for 3-axis CNC finish machining using a ball end mill tool. The results from the developed algorithm are validated using a machining simulation in the virtual environment of an Open-GL based 3D graphical simulator ToolSim [1].

Robotic edge machining with abrasive brushes

The article describes application of an industrial robot with an electric spindle for finish machining of parts made from aluminum alloy V95pchT2 and titanium alloy VT-20 using abrasive brushes. Effects of cutting velocity, brush deformation and supply on machining performance (edge size) and surface quality (positioning and roughness) have been identified. Based on the experimental data, mathematical dependencies have been developed.