Key Engineering Materials Vols. 656-657

Abstract: Magnetic abrasive finishing (MAF) is a fast and high-precision polishing method. However, the magnetic force acting on abrasive particles will decrease remarkably when polishing stainless steel tubes with the property of non-permeability, such as the SUS304 stainless steel. Moreover, the abrasive particles will be moved off the surface of machining area due to the centrifugal force of rotation, resulting in reducing the stability of polishing process. Therefore, this study developed a novel approach by adopting different gels as the bonding materials to combine the magnetic abrasive particles with hard abrasive particles to create a series of magnetic abrasive gels. Generally, those abrasive gels have higher viscosity to dominate the flow property that will constrain uniform motion of the abrasive particles in MAF, and the abrasive gels can be tightly contacted to the wall surface to increase the stability of polishing. This investigation utilized the optimal parameters out of Taguchi method to polish SUS304 stainless steel tube for 30 minutes—the value of surface roughness can be reduced from 0.636μm Ra to 0.05μm Ra, which can be improved by 92.1%, and the amount of material remove rate is as high as 218.4mg.

Abstract: In this study, tool edge temperature was measured by a two-color pyrometer with an optional fiber and the novel method to evaluate the cooling effect of cutting fluid was proposed. After one cut, the tool edge passes over the fine hole at workpiece where inserted into an optical fiber so that the one peak signal can be obtained by each of two detectors with different spectral sensitivities in the pyrometer. The tool edge temperature can be calculated by taking the ratio of outputs from these two detectors. In previous research dealing with the cutting temperature in end milling obtained by a two-color pyrometer with an optional fiber, the average temperature calculated from some large peak values was used for an index as cutting temperature. However, this method was not suitable to estimate the tool edge temperature in wet milling. In the proposed method, the tool edge temperature was calculated only by the peak signals just after full length cut and used for an index as cutting temperature. The frequency distribution of tool edge temperature was made by the obtained temperature data. Comparing dry cutting to wet cutting, there was almost no difference in maximum temperature but obvious difference in the frequency distribution. The temperature range in wet cutting was wider than that in dry cutting.

Abstract: Recently, increasingly high efficiency and high performance have become to be required of information equipment. As a result, optical scanning parts that reduce optical aberrations, scatter, and diffraction are required in laser printers. It is therefore necessary to improve the geometric surface roughness achieved in mirror cutting of Al alloys and eliminate tear-out marks and scratch marks that can be created during the cutting process. In this study, we investigated the effect of tool wear on the occurrence of surface discontinuities in ultra-precision cutting of Al alloys. In our previous studies, a crystal orientation of {110} plane was adopted in cutting an Al-Si alloy (AHS material, 11wt% Si) and Al-Mg alloy (A5186 material, 4.5wt% Mg) using a straight diamond tool. The cutting edge recession that occurs when cutting AHS material has been reported to be approximately 5 times greater than that which occurs when cutting A5186 material. Therefore, we cut the AHS material for accelerated wear and investigated the cutting edge recession, the surface roughness and the cutting force. We found that the cutting edge recession decreases as the tool wear angle γ increase. For example, at a tool wear angle γ = 40°, the cutting edge recession is approximately 7 times greater than that which occurs at a tool wear angle γ = 12°. As the tool wear angle increases, the cutting distance increase, which produces a mirror like surface. In addition, we were able to obtain a good machined surface using a positive tool setting angle because side cutting edge produces residual stock of removal 0.1 μm when the cutting edge recession is 0.3 μm or more and when it is cut by following end cutting edge.

Abstract: The machinability of difficult-to-cut materials was evaluated during the milling process using water soluble and water insoluble cutting oils. The fundamental characteristics of the cutting oils were investigated by the pin-on-disk abrasion test. The machinability was evaluated by the tool flank wear, chip geometry, cutting force, and tool-flank temperature during milling. The tool-flank temperature was measured using a two-color pyrometer with an optical fiber. Workpiece materials consisting of stainless steel and a titanium alloy were used along with commercial cutting oils. From the results of the pin-on-disk abrasion test, the friction coefficients resulting from the application of various cutting oils to the face of the titanium alloy and WC-based hard metal were approximately the same value. The water soluble cutting oil had a higher coolability than the water insoluble cutting oil. From the results of the milling test, the water insoluble oil had a higher machinability of the difficult-to-cut materials than the water soluble cutting oil. The tool-flank temperature during wet cutting of the difficult-to-cut materials decreased by approximately 50–80 °C compared to dry cutting. However, no differences in the tool-flank temperature were observed between the water soluble and water insoluble cutting oils. The cutting force during wet cutting increased compared to dry cutting, most likely because the heating during cutting was reduced by supplying the cutting oil, and the material at the cutting point did not cause heat softening.

Abstract: A fret-saw blade is commonly used in micromachining or curve machining of various woods. However, there is a curvature limit for machining of free-form surfaces because a fret-saw blade has a thickness of several hundred microns and a width of several millimeters. Additionally, cutting with a fret-saw blade produces much wood meal as chips. If a fine wire cutting tool is used, more flexible machining, such as machining of high curvature free-form surfaces, is possible and the quantity of chip production drastically decreases. The main purpose of this study is to clarify the fundamental machinability of anisotropic materials cut with a fine wire tool. In this report, we describe the machinability of various woods that are naturally anisotropic materials using a fine wire cutting tool that has electrodeposited diamond grains on its surface. In addition, this report discusses the performance of a trial manufactured hand tool employing the same wire cutting tool. The main conclusions obtained in this study are as follows. Acceptable machining of anisotropic woods is possible using a fine wire cutting tool, and the kerf width produced with this wire tool is narrower than that produced with a fret-saw blade. Additionally, the wood species and the cutting direction with respect to the wood grain have a significant influence on the machinability of various woods. Moreover, a relatively smooth cross section is provided when wood is cut by the hand tool using the fine wire tool.

Abstract: CFRP and Titanium alloy, which are known as difficult-to-cut materials have been widely used as structural material in aviation industries. The orbital drilling is one of an effective drilling technique for the industries. However this technique has some disadvantages such as increase of cutting force due to cutting with tool center point, inertial vibration generated by revolution and high installation cost. In order to improve the disadvantages, we have invented a new drilling technique which is called inclined planetary motion milling. The inclined planetary motion milling and the planetary mechanism drilling has two axes of cutting tool rotation axis and revolution axis. Cutting tool rotation axis of the orbital drilling is moved parallel to the revolution axis in eccentric. On the other hand, in the case of the inclined planetary motion milling, eccentric of the cutting tool rotation axis is realized by inclination of a few degrees from the revolution axis. Therefore, the movement of eccentric mechanism can be reduced by comparison with the orbital drilling because inclined angle is smaller than eccentricity of the cutting tool tip. As a result, eccentric mechanism can be downsized and inertial vibration is reduced. In the study, a geometrical cutting model of inclined planetary motion milling was set up. The theoretical surface roughness of the inside of drilled holes by use of two types cutting tool geometry were calculated based on the model. And cutting experiments using the new prototype for CFRP were carried out in order to evaluate the effect on machinability with change of cutting point atmosphere. In addition, optimal cutting condition was derived according to cutting experiments for titanium alloys utilizing the orthogonal array.

Abstract: Machining has traditionally been one of the major operations within most manufacturing systems and intelligent machining will play an important role in feature manufacturing systems. This paper concerns the machine learning, specifically classification and recognition of cutting conditions in drilling process. Awareness of the cutting conditions can enhance the auto-diagnosis of an intelligent machining system. In this paper, features representing the drilling process are generated from the converted forms of thrust force and torque and extracted with wavelet packet transform (WPT) and then selected by principal component analysis (PCA). Data instances are generated from experiments with different cutting conditions including workpiece material, drill diameter, feed rate, and spindle speed. A feed-forward network trained with back-propagation method (BPNN) is applied to distinguish between the patterns of each cutting condition. The different contributions of features and the recognition results of cutting conditions are discussed.

Abstract: The environment issue and green machining technique have been induced intensive attention in recent years. It is urgently need to develop a new kind dielectric to meet the requirements for industrial applications. The aim of this study is to develop a novel dielectric using gas media immersed in deionized water for electrical discharge machining (EDM). The developed machining medium for EDM can fulfill the environmentally friendly issue and satisfy the demand of high machining performance. The experiments were conducted by this developed medium to investigate the effects of machining parameters on machining characteristics in terms of material removal rate (MRR) and surface roughness. The developed EDM medium revealed the potential to obtain a stabilizing progress with excellent machining performance and environmentally friendly feature.

Abstract: Near-dry machining attracts increasing attentions for environmental and economical benefits, and MQL machining has been recognized as the most representative near-dry method. It is highly successful in machining of most ordinary steels, and synthetic biodegradable polyol esters play a significant role as an effective cutting fluid with a very small amount. Recent concern for environmentally friendly manufacturing further encourages the attempts at applying near-dry operations to machining of difficult-to-cut materials. Since titanium alloys are typical difficult-to-cut materials, this paper investigates the cutting performance of various near-dry methods in turning of a titanium alloy from the view point of elongating the tool life. Those near-dry methods include regular MQL and hybrid mist supply operations, where the hybrid mist is a mixture of MQL mist and coolant mist which is atomized water-soluble cutting fluid. The regular MQL operation provided considerably long tool life compared with that of dry machining and the hybrid mist operation showed the possibility of making the tool life longer. The cutting performance was largely influenced by the type of MQL lubricants. In particular, a synthetic polyol ester lubricant having low viscosity indicated the successful cutting performance when it was combined with the coolant mist supply in the hybrid mist application.

Abstract: This paper presents shear cutting behaviors in thermosetting and thermoplastic CFRP laminates. Cross-ply laminates were fabricated from unidirectional thermosetting and thermoplastic CFRP prepregs for shear cutting tests. The tests were conducted by using three upper blades (Blades A, B and C) with different clearance and shearing angles at room and elevated temperatures up to around the glass transition temperature T_g. The cross-sections near the cutting surfaces were observed to quantitatively measure the length of burrs and removal part. In addition, double cantilever beam (DCB) tests were performed to measure mode I interlaminar fracture toughness of the thermosetting CFRP at various temperatures. It was found that the optimum cutting for the thermosetting CFRP is achieved by using Blade C at a temperature of 70 ^OC, which is slightly lower than T_g. However, optimum cutting conditions are not proposed for the thermoplastic CFRP yet since the dominant parameters are not always identified under the conditions within the present study.