Cutting technologies have been widely applied in the manufacturing of airplane, automobile, medical, energy, and information industries. Cutting operations are generally evaluated in terms of material removal rates and surface quality. Materials science and engineering has also made significant progress in improving material properties. Therefore, scientific research should be conducted to achieve high performance when working with difficult-to-cut materials such as nickel-based super alloy. Because the manufacturing of products with complex shapes in various industries requires multi-axis machining, the cutting operations should be managed efficiently through controls, simulations, and monitoring.
This special issue was organized by Research Committee of Cutting Technologies in Japan Society for Precision Engineering. This issue includes 14 papers on advanced cutting technologies covering the following topics:
- Modeling the tribological aspects of the tool face–workpiece interface during the cutting process.
- Cutting mechanics in advanced cutting operations.
- Tool wear and coolant supply in cutting of advanced materials.
- Cutting processes for hard materials to improve cutting performance.
- Fixturing, chatter suppression, and tool path generation to control cutting processes and operations.
- Surface characterization and modeling to control product quality in multi-axis machining.
I hope this issue will be helpful for readers to understand cutting processes and improve the cutting operations.
There growing demand for a new FEM cutting simulation method capable of dealing with the peculiar friction phenomena that occur on the interface between work and tool materials. In this report, we first seek a theoretical formula for quasi-dislocation motions as a model to explain the phenomena that occur on the interface between the work and tool materials by applying the dislocation theory. Next, we present our method for deriving the frictional stress on a tool face from quantum mechanical calculations based on the above-mentioned model. It uses the molecular orbital method, which can only conduct static calculations, to obtain the shear stress under high strain velocities. As one of its features, it does not use complicated experiments and the first-principle molecular dynamic calculations that is high costs.
This paper presents a thermodynamic model for studying the energy dissipation processes such as friction, wear, and the adhesion phenomenon in order to predict the built-up layer (BUL) and built-up edge (BUE) formation conditions in dry cutting of SUS304 stainless steel. The model is composed of three parts: the extended representative contact model (RCM) at the tool and chip interface, the thermodynamic analysis within the RCM, and the growth model. At a typical region, the RCM is characterized by three material elements and two boundary elements, which support the contact conditions between two material elements. Thermodynamic analysis within the RCM reveals that apart from friction and wear, the BUL/BUE formation is also an irreversible energy dissipation process. The BUL/BUE can be called as a “dissipative structure substance,” which can reduce tool wear. Meanwhile, the RCM is an open system because it allows for the transfer of energy and matter with its surrounding. Energy exchange and mass exchange exert significant influences on the BUL/BUE growth. It is verified that the BUL/BUE growth depends significantly on four energy dissipation processes: workpiece fracture, friction, workpiece accumulation, and reduction of adhesion. In addition, the proposed model is verified by comparing simulations with the corresponding experimental results of dry cutting of SUS304 stainless steel. It is verified that the BUL/BUE develops its characteristics with cutting time and that the proposed model can accurately predict the BUL/BUE formation conditions. These results have provided a deeper understanding of the BUL/BUE formation mechanisms.
This paper is focused on the cutting performance in the side milling of a small-size end mill with vibrations generated by an ultrasonic vibration spindle apparatus in the axial direction with a helix edge. In side milling with ultrasonic vibration in the rotational direction, the mean value of the cross-sectional chip area per cutting time decreases owing to the frequent repetition of the cutting and non-cutting phases. As a result, the cutting force decreases and provides an optimal cutting performance as compared to that in conventional side milling. First, the cross-sectional chip area is calculated using three-dimensional computer aided design (CAD) with its mean value relative to the cutting time. The ultrasonic vibration spindle apparatus is then attached to the machine spindle, and cutting tests are performed for conventional and ultrasonic vibration machining. Next, the flank wear, surface roughness, cutting force, and residual stress are measured. The results obtained from the cutting tests of the two machining methods are compared. The main results are as follows: (1) A comparison of the flank wears of conventional machining and ultrasonic vibration machining shows that the former is larger than the latter. The maximum flank wear increases as the cutting length increases for both the machining methods. (2) The maximum height of the machined surface in ultrasonic vibration machining is larger than that in conventional machining because of the marks caused by ultrasonic vibration. (3) The mean cross-sectional chip area relative to the cutting time decreases with ultrasonic vibration machining and the tool deformation decreases with a decrease in the mean cutting force relative to the cutting time. (4) With ultrasonic vibration machining, residual stress is generated on the machined surface not only in the feed direction but also in the axial direction because of the repetitive sliding actions in the axial direction of the flank of the cutting edge.
This study describes a new surface treatment method that involves immersing sintered cutting tools into a high-pressure, high-temperature processing liquid. Cutting experiments were performed, and the results show that oil-immersion treatment helps reduce tool wear. However, this treatment limits the applications of treated carbide tools, e.g., they become unsuitable for heavy-cutting conditions. After the cutting test, surface analyses of the treated carbide tools were performed using FT-IR, SEM, EPMA, and XPS to verify the effect of oil-immersion treatment on tool-wear reduction. FT-IR analysis showed that, following oil-immersion treatment, trace quantities of the coolant remained on the tool surface, which could be readily removed by ultrasonic cleaning. Despite the removal of the processing liquid, the tool subjected to oil immersion exhibited less wear than the non-treated tool. SEM and EPMA examinations revealed that oil-immersion treatment reduced the amount of cobalt on the tool surface, forming sulfur deposits. EPMA analysis indicated that less cobalt binder was found on the surface after oil-immersion treatment, suggesting that the reduction in the amount of cobalt caused tungsten carbide particles to be exposed.
In this study, the coolant element deposition on the flank face of a coated tool in the turning of Inconel 718 when the coolant jet was supplied from the tool flank side at coolant pressures from 1 to 20 MPa was investigated. The flank wear-land was inspected after the cutting experiments using energy dispersive X-ray spectroscopy analysis to obtain the mappings of chemical elements contained in the workpiece, coating material, and coolant. It was found that coolant jet with pressures higher than 5 MPa extended the tool life dramatically compared to flood cooling. In contrast, increasing the coolant pressure beyond 5 MPa yielded only marginal improvements of the tool life, as has been reported previously for very high coolant pressures. Trace chemical elements contained in the coolant were mainly detected along the border of the tool-work contact area. The amounts of materials deposited had a complicated relationship with the pressure, and a large amount of sodium, silicon, calcium, and phosphorus deposited at very high coolant pressures of 10 and 20 MPa. It was concluded that the saturation of tool life extension at higher coolant pressures was ascribed to the thick deposited layer of a mixture of compounds, such as calcium phosphate and sodium silicide, along the border, which prevented the high-pressure coolant from penetrating into the tool/work contact area.
Recently, cutting has replaced grinding in the finishing process for hardened steel. However, tool damage is a major problem in high-efficiency operations that use high-speed cutting and high-feed rate conditions rather than more conventional cutting conditions. Therefore, a new cutting technique that can realize high-efficiency cutting is desired. In our previous study, the processing efficiency was improved three to five times compared with conventional hardened steel cutting by driven rotary cutting. Furthermore, to attain high efficiency, the resistance of the tool material to wear and oxidation must be improved. In this study, the cutting performance of tools with an Al-rich coating, which improves oxidation resistance, is investigated for high cutting speed applications. In the present experiments, the flank wear of the Al-rich tool was less than 40 μm at a high cutting speed of 2.51 m/s, even for a cutting length of 10.0 km. Additionally, the Al-rich tool wear advanced progressively without flaking. In contrast, the conventional TiAlN-coated tools exhibited serious failure at cutting lengths of 3.0 km. It is thought that the difference in the oxidation resistance of the two tools influenced the cutting performance. Therefore, the tool with the Al-rich coating can operate with a high efficiency even at high cutting speeds.
This study investigates the cutting characteristics of direct milling of cemented tungsten carbides performed using a diamond-coated carbide end mill. The diamond-coated carbide end mills have cutting edges that are both treated and untreated, and the sharp cutting edge can be developed at the ridgeline of the diamond coating on the flank face via treatment of the cutting edge. Two types of cemented tungsten carbide were used as workpiece materials, i.e., TAS VM-40 and VC-70. The influence of the cutting length on the cutting characteristics was also studied. In the case of cutting of the VM-40, the cutting force of the treated tool was significantly lower than that of the untreated tool. The cutting forces of both tools were observed to be similar after the diamond coating on the rake face of the untreated tool was flaked. The cutting edge at the ridgeline of the diamond coating on the flank face of both tools was retreated during the cutting progress, and the thickness of the diamond coating of the untreated tool was also decreased. The finished surface integrity was drastically altered owing to the flaking of the diamond coating on the rake face of the untreated tool and the irregularity of the cutting edge of both tools. The accuracy of the machined shape obtained by using the treated tool was better than that obtained using the untreated tool, and the tendency was significantly observed as the cutting progressed. In the case of cutting of VC-70, flaking of the diamond coating of untreated tool did not occur, and the cutting force of the treated tool was significantly lower than that of the untreated one. The cutting edge of the treated tool was maintained sharp up to a groove length of 500 mm, although the workpiece material was clearly observed to be adhering to the round corner of the cutting edge of the untreated tool. Moreover, the accuracy of the shape of the machined groove obtained using the treated tool was better than that obtained using the untreated tool.
Die and mold are necessary for the manufacture of present industrial products. In recent years, the requirement of high quality and low cost machining of complicated surfaces has increased. However, it is difficult to generalize process planning that depends on skillful experts and decreases the efficiency of preparation in die and mold machining. To overcome an issue that is difficult to generalize, it is well known that neural networks may have the ability to infer a valid value based on past case data. Therefore, this study aims at developing a neural network based process planning system to infer the required process parameters for complicated surface machining by using past machining information. The result of the conducted case studies demonstrates that the developed process planning system is helpful for determining the tool path pattern for complicated surface machining according to the implicit machining knowhow.
There is a high demand for microdrilling processes to drill microholes with diameters equal to or less than 0.2 mm for use in fuel injection nozzles. In this study, nonstep drilling methods are developed for high-efficiency processing. Herein, the effects of the cutting oil supply method and the drill’s feed rate on the developed thrust force and torque during drilling are investigated. Accordingly, it is shown that drop supply of the cutting oil is the optimal method for nonstep drilling because the oil is sucked into the microhole. Furthermore, a high-feed rate is preferred because it produces continuous chips.*
* This paper is a translation with revision of the paper: M. Uchiyama and N. Sakata, “Cutting capability of micro drills in non-step drilling 1st report: Optimization of cutting oil supply and drill feed,” J. of the Japan Society for Abrasive Technology, Vol.59, Issue 1, pp. 27-31, doi: 10.11420/jsat.59.27, 2015 (in Japanese).
Parallel turning technology has been attracting attention as an important technology to enhance the productivity of multitasking machine tools. To maximize the productivity advantage of parallel turning, chatter avoidance or suppression is one of the most noteworthy concerns. In this study, a novel chatter suppression technique using tool swing motion is provided by a feed drive system. The optimal design methodology of the tool swing motion for effective chatter suppression is also introduced based on its analogy with the spindle speed variation technique under the shared-surface parallel turning and rigid-tool and flexible-workpiece assumptions. The proposed method was evaluated with regard to the chatter stabilizing performance and workpiece runout as compared to conventional equal pitch turning and unequal pitch turning for chatter suppression. As a result, the proposed tool swing parallel turning exhibited a high chatter stabilizing performance without eccentricity of the workpiece and enhanced surface quality, although particular swing marks were left on the machined surface.
Many mechanical parts have complicated and delicate shapes for improving their functionality and designability. To machine thin parts with high accuracy, it is necessary to reduce the cutting force induced on the workpiece or to clamp the workpiece optimally. Generally, cores are placed in the workpiece to fix it firmly at the production site. However, the cores must be adjusted precisely in accordance with the shape of the workpiece. A low-point melting alloy can be conveniently used instead of the cores. In this study, the influence of the supporting method for thin parts having a curved surface using a low-melting point alloy on machining accuracy is experimentally investigated. The turbine blade is selected as the experimental part. The shape is produced via end milling. The experimental results indicate that a low-melting point alloy can be closely fitted to the supporting curved surface of the turbine blade because the volume of the low-melting point alloy increases in the solidification. However, the machining accuracy is degraded when the turbine blade is deformed owing to the characteristics of the low-melting point alloy. A support method using the low-melting point alloy and an elastomer support is proposed to improve the machining accuracy. The effectiveness of the proposed method is experimentally confirmed.
Novel end mills with micro-scale structures have recently been developed to promote cutting performances with cutting forces, chip controls, and tool wears. However, the surface profiles are formed corresponding to the structures on the tool edges. The surface finishes, therefore, are worse than those of cuttings with straight edges of the end mills. This paper discusses surface profiles in milling with the structured tool and the cutter axis inclination. An analytical model is presented to simulate the surface profiles for the tool edge shape, the cutting parameters and the cutter axis inclination. Because the surface profiles are controlled in the simulation, the optimum cutting parameters are determined to reduce the surface roughness. Micro-scale nicks were fabricated on polycrystalline diamond edges with a laser machine tool. The sizes and pitches of the nicks were controlled by the laser processing parameters. The cutting tests were conducted to measure the surface profiles. The presented surface profile model was validated by comparing the simulated and the measured surface roughnesses. The surface finish can be improved in milling with the cutter axis inclination in the optimum cutting parameters.
High-precision machining is required for manufacturing hyper-hemispherical artificial joints made of difficult-to-cut metals such as cobalt-chromium (Co-Cr) alloys to provide wear resistance in the human body. The hyper-hemisphere of Co-Cr alloys is finished by curve generator machining, in which the rotation axes of the cutter and workpiece intersect each other at the center of the sphere to be machined. This paper presents a kinematic model to simulate the shape and surface topography on hyper-hemispheres with the cutter loci in curve generator machining. The kinematic model was validated with a cutting test, in which the surface profiles were measured around the pole and equator of the sphere. Simulations were performed to study the cutting process and surface finish. The appropriate cutting parameters were determined to improve the surface finish based on a kinematic simulation. A smooth surface was obtained when small inclinations of the workpiece, large nose radii of the cutter, low workpiece rotation speeds, and non-integer ratios of the tool spindle speed to the workpiece rotation speed were employed. The effects of the setting errors, such as the mounting error of the cutter and alignment error of the spindle and workpiece axes, were estimated via the kinematic simulation. It was found that the surface topography and radius of the sphere depended on the setting errors. The radius and center of the spherical shape were different from those of an ideal sphere by an error in the X-axis in the global coordinate system. The oval shape was caused by an error in the Y-axis. An error in the Z-axis affected the radius of the machined sphere.
A surface with stratified functional properties (hereafter, referred to as the “plateau surface”) improves the tribological characteristics of sliding surfaces in machine tools, automobile parts, engines, etc. The evaluation methods of the plateau surface are listed in the ISO 13565 standard. However, since the evaluation methods listed in ISO 13565-3 are associated with several problems, these evaluation methods have been rarely used in production management. A plateau surface evaluation method that applied image recognition technology was developed in previous research studies to solve these problems. However, this method is time consuming with a calculation time of approximately 20 s. Therefore, in this research, we developed a new plateau surface evaluation method that applied the fast M-estimation type Hough transformation to achieve a computational time of a few seconds. It is expected that this method will be used in mass production processes.
In this paper, a method using electrical contact resistance to monitor in-process tool wear is proposed. The high-speed tool wear detection system uses the contact resistance between the tool and workpiece as an indicator to monitor the progression of tool wear during cutting operations. The electrical resistance decreases with an increase in contact area on the tool flank. In our previous study, the objective was an end milling process using uncoated square end mills. In this experiment, our targets are solid and throw away coated square end mills. The experiment shows the present method to also be effective as an in-process tool wear detection system for coated square end mills.
To date, various in-process monitoring and measuring techniques for milling have been proposed; these are based on factors such as spindle power, cutting force, and vibration. However, the spindle power and cutting force in small-diameter milling processes are too small, thereby rendering these methods ineffective. This study aims to develop an in-process monitoring system of the cutting state, and thus, prevent tool breakage in milling when using a small-diameter tool. Our previous study showed that this monitoring technique is based on the analysis of the tool projection image by a CCD camera. It enables a precise measurement of tool deflection during high-speed milling. In this study, we apply this system to the measurement of tool deflection in end milling under different cutting conditions, including tool type, machining shape, workpiece, and feed rate. Moreover, we examine the relationship between tool deflection and cutting conditions. The results clarify that this system enables in-process monitoring of tool deflection. The measured tool deflection with this system is influenced by the cutting condition. In addition, the tool deflection shows a periodical change in one turn, which seems to be related to the number of tool edges.
An active air thrust bearing controlled by an Arduino board and digital valves is described. A numerical model for the complete system is developed to design the control and perform a sensitivity analysis based on geometric parameters such as the conductance of the valves. Model validation is based on experimental open-loop and closed-loop tests. The purpose of the model is to determine the range of force and air gap height in which the pad can be controlled.
Detailed description of the multi-axis repeatability performance and the modelling of non-systematic variations in the positioning performance of machine tools can support the understanding of root-causes of capability variations in manufacturing processes. Kinematic characterization is implemented through repeated measurements, which include variations related to the performance of the machine tool. This paper addresses the integration of the positional repeatability in kinematic modelling through the employment of direct measurement results. The findings of this research can be used to develop standardized approaches. The statistical population of random errors along the multi-axis travel first requires the proper management of experimental data. In this paper a methodology and its application are presented for the determination of repeatability under static and unloaded conditions as an inhomogeneous parameter in the work space. The proposed approach is demonstrated in a case study, where the component errors of a linear axis are investigated with repeated laser interferometer measurements to quantify the estimated repeatability and express it in the composed repeatability budget. The conclusions of the proposed methodology outline the sensitivity of kinematic models relying on measurement data, as the repeatability of the system can be in the same magnitude as the systematic errors.
In this paper, the author reports an upgraded high-pressure air compression unit that can be fixed inside a press die to supply strong air. This can be used as an auxiliary power source by utilizing the reciprocating motion of a press machine. The new unit was developed based on the first generation trial product made two years ago. It adopted a simpler structure that can easily be installed in a normal standard die set, and that generates more powerful compressed air than before. Increasing air pressure and holding experiments were performed, and the results showed that the maximum value of high-pressure air generated reached several tens of times the usual air pressure a workshop is equipped with. This proposition provides the possibility of using self-generated air as an auxiliary power source to finish accompanied actions in pressing processes, such as material feeding, blowing down cutting slugs, and even executing second workings for shape forming. This technology converts a part of the excessive energy from a press machine to air power, and its applications are expected to improve the productivity of press workings.